Results - Part 4

Vectorborne diseases

Vectorborne diseases are infections transmitted by arthropods such as such as mosquitoes and ticks. A vectorborne disease may involve a simple transfer via the arthropod, or may involve replication of the disease-causing organism in the vector.¹⁴ Vectorborne diseases of public health importance in Australia listed in this chapter are; arbovirus not elsewhere classified (NEC), Barmah Forest virus (BFV) infection, dengue virus (DENV) infection, Japanese encephalitis virus (JEV) infection, Kunjin virus (KUNV) infection, malaria, Murray Valley encephalitis virus (MVEV) infection and Ross River virus (RRV) infection. The vectorborne diseases yellow fever virus (YFV) infection, plague and certain viral haemorrhagic fevers are listed under quarantinable diseases. The National Arbovirus and Malaria Advisory Committee (NAMAC) provides expert technical advice on vectorborne diseases to the Australian Health Protection Principal Committee through the CDNA. NAMAC provides a detailed report of vectorborne diseases of public health importance in Australia by financial year.⁷⁰

Alphaviruses

Viruses in the genus Alphavirus that are notifiable in Australia are BFV and RRV. These viruses are unique to the Australasian region.⁷¹ Infection can cause a clinical illness, which is characterised by fever, rash and polyarthritis. The viruses are transmitted by numerous species of mosquito that breed in diverse environments.⁷² The alphavirus chikungunya is not nationally notifiable, and thus not included in this annual report, but it is notifiable in all states and territories except the Australian Capital Territory, and states and territories send information about cases to the Commonwealth for national collation and analysis.^70,73

The national case definitions for RRV and BFV require only a single IgM positive test to one of them, in the absence of IgM to the other.⁷⁴ False positive IgM diagnoses for BFV in particular are a known issue, and it is unclear what proportion of notifications might represent true cases. There was a large increase in notifications of BFV nationally subsequent to this reporting period (occurring from October 2012), which is suspected to be due to false positive notifications. This is under investigation and the laboratory case definition is under review.

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Barmah Forest virus infection

Epidemiological situation in 2011

In 2011, there were 1,870 notifications of BFV infection, for a rate of 8.3 per 100,000 population. This compares with a 5-year mean of 1774.0 notifications and a 5-year mean rate of 8.3 per 100,000.

Seasonality and place of acquisition

The seasonality of BFV notifications is less marked than for RRV, and a high proportion of interseasonal notifications are thought to be due to false positive diagnoses. Peak notification of BFV during the period 2006 to 2011 was between January and April, and 47% of cases were diagnosed during these months (compared with 57% for RRV).

Most notifications of BFV infection are from Queensland and New South Wales (78% of all cases from 2006 to 2011), but rates are highest in the Northern Territory. The number of BFV notifications increased markedly in Victoria between December 2010 and March 2011, and the notification rate for 2011 was 4.9 times the 5-year mean (Figure 62).

Figure: 62: Notifications of Barmah Forest virus infection, Australia, 2006 to 2011, by month and year and state or territory

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Age and sex distribution

BFV was most frequently reported in middle aged adults (median 46 years, range 0–90 years). Age specific rates were highest amongst the 60–64 year age group for males and the 55–59 year age group for females (Figure 63).

Figure: 63: Notification rates for Barmah Forest virus infection, 2011, by age and sex (n=1,869)*

* Sex was not available for 1 case, and this case is excluded from the figure.

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Ross River virus infection

Epidemiological situation in 2011

In 2011, there were 5,166 notifications of RRV, giving a rate of 22.8 per 100,000. This compares with a 5-year mean of 5060.4 notifications and a 5-year mean rate of 23.6 per 100,000.

Seasonality

Peak transmission for RRV during the period 2006 to 2011 occurred between January and April, and 57% of cases were diagnosed during these months.

Between 2006 and 2011, nearly half of all RRV infections were from Queensland (44% of all cases), but rates were highest in the Northern Territory. Significant increases in the number and rate of reported cases were noted in Victoria and South Australia (Figure 64), where rates were 6.0 and 3.2 times the 5-year mean, respectively.

Figure: 64: Notifications of Ross River virus infection, Australia, 2006 to 2011, by month and year and state or territory

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Over the spring and summer of 2010–11 the south-east of Australia experienced unusually wet weather and flooding resulting in increased mosquito and wild bird numbers. The noted increases in reporting of RRV occurred in the context of widespread evidence of seroconversions in sentinel chickens to flaviviruses and outbreaks of arboviral disease (KUNV and RRV) in horses, and equine cases were widely distributed across Victoria and New South Wales, and also in south-eastern parts of South Australia and Queensland and south-western parts of Western Australia.⁷⁵ Between January and June 2011, there were 982 clinically apparent cases of arboviral disease in horses and 91 horses died.⁷⁵ RRV infections predominated in equines in Victoria, and formed a significant proportion of infections in South Australia.⁷⁵

Age and sex distribution

RRV was most frequently reported in middle aged adults (median 43 years, range 0–92 years). Age specific rates were highest amongst the 50–54 year age group for females, and the 40–44 year age group for males (Figure 65).

Figure: 65: Notification rates for Ross River virus infection, 2011, by age and sex (n=5,164)*

* Sex was not available for 2 cases, and these are excluded from the figure.

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Flaviviruses

In Australia, flavivirus infections of particular public health importance are DENV, KUNV, MVEV and JEV. YFV is reported under Quarantinable diseases. Unspecified flavivirus infections are reported under arbovirus NEC. These infections are nationally notifiable.

DENV has 4 serotypes, each containing numerous genotypes, and the serotypes isolated from returning travellers (and thus involved in local outbreaks) vary by year and geographical region. Infection with 1 serotype probably confers lifelong immunity to that serotype,¹⁴ but subsequent infection with a different serotype is one factor thought to increase the risk of severe outcomes, along with the infecting serotype and genotype and host factors.^14,76–78 The clinical illness is characterised by mild to severe febrile illness with fever, headache, muscle/joint pain and sometimes a rash. A minority of cases progress to severe dengue with haemorrhage and shock. Aedes aegypti is the major vector of DENV in Australia.

Infection with MVEV, KUNV or JEV is usually asymptomatic or produces a non-specific illness, but a small percentage of cases progress to encephalomyelitis of variable severity. Culex annulirostris is the major vector of MVEV, JEV and KUNV. No specific treatment is available for these diseases and care is largely supportive. A vaccine is available to prevent JEV infection,⁴⁴ but there are no vaccines currently for DENV, MVEV or KUNV infection.

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Arbovirus NEC

Epidemiological situation in 2011

In 2011, there were 24 notifications of arbovirus NEC, compared with an average of 18 cases during the previous 5 years. These notifications comprised chikungunya (1 case), flavivirus unspecified (14 cases), Kokobera (1 case), Stratford (1 case), and the infecting organism was unknown or not supplied for a further 6 cases (Table 14).

Table: 14: Notifications of arbovirus NEC, Australia, 2011, by infecting organism and state or territory

Virus	ACT	NSW	NT	Qld	SA	Tas.	Vic.	WA	Total
Chikungunya	0	0	1	0	0	0	0	0	1
Flavivirus	0	0	0	0	0	0	14	0	14
Kokobera	0	0	0	2	0	0	0	0	2
Stratford	0	0	0	1	0	0	0	0	1
Unknown	0	0	0	6	0	0	0	0	6
Total	0	0	1	9	0	0	14	0	24

The majority of notifications in 2011 were from Victoria (14 cases), with the remainder being from Queensland (9 cases) and the Northern Territory (1 case). Information about the place of acquisition was available for 63% of cases (15/24), and all of these were acquired overseas.

The median age of cases was 30 years (range 15–72 years).

Dengue virus infection

Local transmission of dengue in Australia is normally restricted to areas of northern Queensland where the key mosquito vector, Ae. aegypti is present.^44,79,80 Dengue is not endemic in North Queensland, but local transmission can occur upon introduction of the virus to the mosquito vector by a viraemic tourist or a resident returning from a dengue-affected area overseas.⁸⁰

Epidemiological situation in 2011

There were 817 notifications of DENV infection in 2011, compared with 1,246 in 2010, and a 5-year mean of 737.8 cases. Most infections were acquired overseas (n=727) (Figure 66). There were 76 infections acquired in Australia. For a small number of cases (n=14), no information was supplied on the place of acquisition.

Figure: 66: Notifications of dengue virus infection, Australia, 2006 to 2011, by month and year and place of acquisition

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Serotype of dengue virus infections

Historically, imported and locally-acquired cases of DENV have involved all 4 serotypes. In 2011, serotype information was available for 51% of notifications (413/817), which was unchanged compared with the 5-year mean (51%). In 2011, 37% (130/352) of overseas-acquired cases with a known serotype were DENV serotype 1, and 32% (112/352) were DENV 2, similar to the 5-year mean of 33% for each (Table 15). Locally-acquired cases were most commonly DENV 2 (51%, 39/76) followed by DENV 1 and DENV 4 (each comprising 10%, 10/76), DENV 3 (1%, 1/76), and for 16 notifications, the infecting serotype was unknown.

Table: 15: Serotype of overseas acquired dengue virus cases, 2011, by serotype and place of acquisition

	Serotype
Country	DENV 1	DENV 2	DENV 3	DENV 4	Unknown/ untyped	Total
Indonesia	107	87	51	29	185	459
Thailand	5	3	17	2	58	85
India	2	2	1	0	22	27
Philippines	3	0	1	2	17	23
Malaysia	4	4	1	0	12	21
Papua New Guinea	3	4	2	0	6	15
Sri Lanka	2	0	1	0	10	13
Vietnam	1	3	1	0	8	13
East Timor	0	2	1	0	9	12
Bangladesh	1	2		0	8	11
Other countries	2	5	1	0	37	45
Unknown countries	0	1	0	0	2	3
Total	130	113	77	33	374	727

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Seasonality and place of acquisition

There were 727 DENV infections known to have been acquired overseas in 2011, down from 1,104 in 2010, which was the largest number of overseas-acquired cases since the disease was made nationally notifiable in 1991. Between 2006 and 2009, the number of cases known to have been acquired overseas ranged between 142 and 474. In recent years, improved diagnostic techniques, in particular the availability of the rapid NS1 antigen detection kit, have improved detection and would have contributed to the observed increase in reported numbers of overseas-acquired dengue in Australia,⁸¹ along with the dramatic re-emergence and geographical expansion of dengue overseas over the past 50 years and explosive outbreaks.⁷⁸

For 14 cases (2%), no information on the place of acquisition was available (Figure 66). Complete information on the country or region of acquisition was available for 98% (724/727) of overseas-acquired cases in 2011, compared with the 5-year mean of 82%. Cases acquired in Indonesia continue to account for the largest number and proportion of all notifications (Table 15), but in 2011, the number decreased to 459 cases acquired in Indonesia (63% of overseas acquired cases with a known country of acquisition), from 711 (63%) in 2010. Other frequently reported source countries in 2011 included Thailand, India and the Philippines.

Most of the 76 locally-acquired cases in 2011 were known to have been associated with one of 3 outbreaks of locally-acquired infection that occurred in Queensland in 2011. The largest of these was an outbreak of DENV 2 in Cairns and Innisfail, and was related to an importation from Papua New Guinea in 2010.⁷⁰ An outbreak of 13 cases of DENV 4 occurred in Innisfail between January and March, but the source of the outbreak was unknown and an outbreak of 9 cases of DENV 1 in Townsville was linked to an importation from Bali.⁸² One locally-acquired case in Western Australia was health-care associated; a physician in Perth sustained a needle-stick injury whilst taking blood, 5 days prior to symptom onset.⁸³

The peak months for overseas-acquired dengue in 2011 were December, January and February, together accounting for 49% of cases. For locally-acquired cases, 95% of cases were diagnosed between January and March 2011.

Age and sex distribution

DENV infections acquired overseas in 2011 were most commonly reported amongst younger and middle aged adults (median 37.5 years, range 0–86 years), with a peak of notifications amongst males aged 20–24 and 25–29 years and females aged 25–29 years (Figure 67). Males and females each comprised 50% of overseas acquired cases. For locally-acquired cases, infections were more commonly reported amongst middle aged and older adults (median 43 years, range 2–78 years), with peak notifications amongst males and females aged 40–44 years (Figure 68). Males and females each comprised 50% of locally-acquired cases.

Figure: 67: Notifications of overseas-acquired dengue, 2011, by age and sex (n=723)*

* Age was not available for 1 case.

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Figure: 68: Notifications of dengue virus infection acquired in Australia, 2011, by age and sex (n=76)

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Kunjin virus infection

Epidemiological situation in 2011

In 2011, there were 2 notifications of KUNV infections in Australia, compared with an average of 1.8 cases per year between 2006 and 2010.

The first case, with onset in April 2011, was a 60-year-old man from the Northern Territory who was IgM positive for KUNV and negative for MVEV, BFV and RRV. The infection was acquired in the Barkly region. The case was non-encephalitic, and recovered from infection.⁷⁰

The second case, with onset in December 2011, was in a 44-year-old female from New South Wales who seroconverted to KUNV and was negative for BFV and RRV. The specific region in which the case was likely to have been exposed was unclear, but the case was a resident of the South Coast of New South Wales.

There were only 11 cases of KUNV infection between 2006 and 2011, and the median age of these cases was 41 (range 20–80 years) and 64% of cases (7/11) were male (Table 16).

Table 16: Notifications of Kunjin virus infection, Australia, 2006 to 2011, by month and year

Year	Month	State or territory of residence	Age group	Sex
2006	March	WA	25–29	Female
2006	April	WA	20–24	Male
2006	April	Qld	40–44	Female
2007	October	Vic.	55–59	Male
2008	July	Qld	30–34	Male
2009	February	Qld	25–29	Male
2009	March	NT	35–39	Female
2010	February	Qld	40–44	Male
2010	June	NT	80–84	Male
2011	April	NT	60–64	Male
2011	December	NSW	40–44	Female

While there was a large number of equine cases of KUNV infection during the previously mentioned outbreak of arboviruses in horses (see RRV infections, Epidemiological situation), there was only 1 human case during the outbreak period (February to August 2011),⁷⁵ and the human case acquired the infection outside the areas where equine cases were reported.

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Japanese encephalitis virus infection

There were no notifications of JEV infection in 2011. The last notified case was in 2008 and was acquired overseas.

Murray Valley encephalitis virus infection

Epidemiological situation in 2011

In 2011, there were 16 notifications of MVEV infection, compared with a 5-year mean of 1.4 cases. A confirmed case in a Canadian resident that was acquired in Australia and diagnosed in Canada was not notified to the NNDSS. Details of ^{these cases have been reported elsewhere.70}

The outbreaks of MVEV infection in humans occurred in the context of the previously mentioned widespread evidence of seroconversions in sentinel chickens to flaviviruses and outbreaks of arboviral disease (KUNV and RRV) in horses (see RRV infections, Epidemiological situation).⁷⁵

Seasonality and place of acquisition

Twelve of the 16 notified cases were acquired in areas of regular enzootic viral activity (the Pilbara and Kimberley regions of Western Australia, and the northern two-thirds of the Northern Territory), or where epizootic disease activity is not unexpected (the Midwest and Goldfields region of Western Australia).⁷⁰ For the remaining 4 cases, the infection was acquired in areas where epizootic activity is rare (New South Wales, South Australia).

Of the confirmed cases, 15 (94%) had dates of onset between March and May 2011 (Figure 69).

Figure: 69: Notifications of Murray Valley encephalitis virus infections, Australia, 2006 to 2011, by month and year and notification status

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Age and sex distribution

In 2011, the median age of confirmed MVEV cases was 31 years (range 1–67 years) and there were equal numbers of cases in males and females.

Malaria

Malaria is caused by a protozoan parasite in the genus Plasmodium, and 5 species are known to infect humans; Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium knowlesi,^14,84 Malaria is a serious acute febrile illness that is transmitted from person-to-person via the bite of an infected mosquito of the genus Anopheles. Malaria is the most frequently reported cause of fever in returned travellers world-wide.⁸⁵ Australia was declared free of malaria in 1981,⁸⁶ but suitable vectors are present in Northern Australia, and the area remains malaria-receptive. A recent case series in the Northern Territory showed that malaria cases were reported in travellers returning from endemic areas, but also reflected current events such as military operations and increased refugee arrivals from particular areas.⁸⁷

Epidemiological situation in 2011

There were 411 notifications of malaria in Australia in 2011, an 18% decrease compared with a 5-year mean of 550.4 cases, and continuing the trend of decreasing notifications since 2005 (Figure 70). The largest number of cases was reported by Queensland (137 cases), but population rates were highest in the Northern Territory (10.0 per 100,000).

Figure: 70: Notifications of malaria, Australia, 2006 to 2011, by month and year and place of acquisition

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Seasonality and place of acquisition

Most infections in 2011 were acquired overseas, but 6 locally-acquired cases were associated with an outbreak in the Torres Strait in April 2011.⁸⁸ The last outbreak of locally-acquired infection on the mainland was in North Queensland in 2002.⁸⁹

Complete information on the country or region of acquisition was supplied for all but one of the cases known to have been acquired overseas, and the remaining cases were listed as overseas, country unknown. The most frequent country of acquisition was Papua New Guinea (28% of cases with complete information) and the most frequent infecting species was P. falciparum (reported in 54% of cases with complete information) (Table 17). No place of acquisition was supplied for cases that are classified as ‘Unknown’.

Table: 17: Notifications of malaria, Australia 2011, by infecting species and country of acquisition

	Malaria species
Place of acquisition	P. falciparum	P. malariae	P. falciparum and P. malariae	P. ovale	P. vivax	Plasmodium unspecified	Total
Papua New Guinea	34	4		2	55	3	98
India	2				41	3	46
Sudan	21			1		1	23
Uganda	18		1	3			22
Tanzania	21			1			22
Ghana	20						20
Indonesia	5				12		17
Sierra Leone	14	1			1		16
Australia	7						7
Other countries	55	5	1	4	30	3	98
Unknown	24	1	0	1	15	1	42
Total	221	11	2	12	154	11	411

There was no discernible seasonality in notifications between 2006 and 2010, but in 2011, 13% of notifications were for cases diagnosed in January, compared with 6% to 10% of cases each month over the previous 5 years. This appears to have been due to an increase in cases from Papua New Guinea (23/55 cases notified in January 2011). The outbreak of malaria reported in the Torres Strait related to people moving between Papua New Guinea and the Torres Strait and occurred in March and April 2011,⁸⁸ shortly after the observed increase in imported cases from Papua New Guinea in January 2011.

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Infecting species for malaria infections

The infecting species was supplied for 97% (400/411) of cases in 2011 (Table 17). P. vivax was associated with Asia and the Pacific, whilst most cases acquired in African countries were P. falciparum.

Age and sex distribution

In 2011, malaria was most commonly reported in males (74%, 303 of the 409 cases for whom sex was stated) with a peak of notifications in males in the 20–24 and 25–29 year age groups (Figure 71). The median age of cases was 32 years (range 2–85 years).

Figure: 71: Notifications of malaria, Australia, 2011, by age group and sex (n=409)*

* Two cases for whom sex was not supplied are excluded from the figure.

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Zoonoses

Zoonoses are those diseases and infections that are naturally transmitted between vertebrate animals and humans.⁹⁰ Approximately 60%–70% of emerging human infectious diseases are zoonoses ^91,92,93 and more than 70% of emerging zoonoses originate from wildlife.⁹² An emerging zoonosis is defined by WHO as ‘a zoonosis that is newly recognised or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range’.⁹⁴

The zoonoses notifiable to the NNDSS included in this chapter are: anthrax, Australian bat lyssavirus (ABLV), lyssavirus (unspecified) infection, brucellosis, leptospirosis, ornithosis, Q fever, and tularaemia.

Several zoonoses notifiable to the NNDSS are included under other headings in this report. For example, Salmonella and Campylobacter infections are typically acquired from contaminated food and are listed under the gastrointestinal diseases section. Rabies is listed under Quarantinable diseases.

Anthrax

Anthrax is caused by the bacterium Bacillus anthracis and mainly causes cutaneous infection. However, it can also cause gastrointestinal and respiratory infections. Anthrax is primarily a disease of herbivores; humans and carnivores are incidental hosts. It can be an occupational hazard for veterinarians, and agriculture, wildlife and industry livestock workers who handle infected animals or by-products.

In Australia, the areas of anthrax risk are well defined and include the northern and north-eastern districts of Victoria and central New South Wales.⁹⁵ Anthrax occurs only sporadically in livestock in the at-risk areas, and rare or isolated incidents or cases have historically occurred in Queensland, South Australia, Tasmania and Western Australia.⁹⁵

Epidemiological situation in 2011

There were no notifications of anthrax in 2011. Over the previous 10 years, only 3 human cases of anthrax were reported in Australia; in 2006, 2007 and 2010.^96–98 All had domestic farm or animal related exposures and all were cutaneous anthrax. Australia has never recorded a human case of inhalational or gastrointestinal anthrax.

There were no reports of anthrax in livestock in Australia in 2011, and the last reported case of anthrax in livestock was in November 2010.⁹⁹

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Australian bat lyssavirus and lyssavirus (unspecified) infections

ABLV belongs to the genus lyssavirus, which also includes the rabies virus. Both invariably result in progressive, fatal encephalomyelitis in humans.¹⁰⁰ ABLV was identified in Australia in 1996 ^101,102 and is present in some Australian bats and flying foxes. Australia is free of terrestrial rabies.

The best way to prevent ABLV infection is to avoid contact with bats. For people whose occupation (including volunteer work) or recreational activities place them at increased risk of being exposed to ABLV, rabies virus vaccine is effective in preventing infection. Pre-exposure vaccination with rabies virus vaccine is recommended for bat handlers, veterinarians and laboratory personnel working with live lyssaviruses.¹⁰³ Post-exposure prophylaxis for ABLV consists of wound care and administration of a combination of rabies virus vaccine and human rabies virus immunoglobulin (HRIG), depending on exposure category and prior vaccination or antibody status.^44,103

Epidemiological situation in 2011

There were no notifications of ABLV or lyssavirus (unspecified) in Australia in 2011. Subsequent to this reporting period, a fatal case of ABLV infection was reported in Queensland in 2013, for a total of 3 cases of ABLV infection in humans (1996, 1998 and 2013). All cases occurred after close contact with an infected bat and all were fatal.^104,105,106 In 2013, the Queensland Department of Agriculture, Fisheries and Forestry confirmed ABLV infection in 2 horses on a Queensland property. These were the first known equine cases of ABLV infection.^107,108 The Bat Health focus group in the Australian Wildlife Health networks gathers and collates information from a range of organisations on testing of bats for ABLV. In 2011 there were 7 ABLV detections compared with 9 detections in bats during 2010.¹⁰⁹

There were also no notifications of rabies (see Quarantinable diseases chapter).

Brucellosis

Brucella species that can cause illness in humans include Brucella melitensis acquired from sheep and goats, Brucella suis from pigs and Brucella abortus from cattle. B. abortus was eradicated from Australian cattle herds in 1989 and B. melitensis has never been reported in Australian sheep or goats.⁹⁵ Therefore, all cases of B. melitensis or B. abortus in Australia are related to overseas travel. B. suis is confined to some areas of Queensland, where it occurs in feral pigs. Eales et al (2010) found that feral pig hunting was the most common risk factor for infection for brucellosis cases in Townsville during 1996 to 2009.¹¹⁰

Internationally, brucellosis is mainly an occupational disease of farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.¹⁴

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Epidemiological situation in 2011

In 2011, there were 39 notifications of brucellosis (a rate of 0.2 per 100,000) compared with the 5-year mean of 37 notifications between 2006 and 2010. Seventy-seven per cent of notifications were from Queensland (30/39) (Figure 72), a state-specific rate of 0.7 per 100,000. Since 1991, 84% of notifications have been from Queensland.

Figure 72: Notifications of brucellosis, Australia, 2006 to 2011, by month and year of diagnosis and state or territory*

* No notifications from the Australian Capital Territory, the Northern Territory, South Australia or Tasmania in 2011.

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The species of the infecting organism was available for a third of notifications (n=13). Eight notifications were for B. suis, all of them from Queensland, with 7 of 8 males aged between 17 and 45 years. There were 5 overseas-acquired cases of B. melitensis, with the country of acquisition listed as India (n=2), Syria (n=1), Turkey (n=1) and an unspecified overseas country (n=1).

The median age of notified cases of brucellosis was 30 years (range 11–77 years) and 82% of cases (32/39) were male.

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Leptospirosis

Leptospirosis is caused by spirochaetes of the genus Leptospira, which is found in the genital tract and renal tubules of domestic and wild animals. In affected areas, where there is exposure to infected urine of domestic and wild animals, this disease can be an occupational and recreational hazard (such as in certain agricultural sectors and swimming or wading in contaminated water).^111,112 The last reported death in Australia attributed to leptospirosis was in 2002.¹¹³

Epidemiological situation in 2011

In 2011, there were 217 notifications of leptospirosis (a rate of 1.0 per 100,000), a 71% increase compared with the 5-year mean of 127.4 notifications (2006–2010). Cases were reported in all jurisdictions, with Queensland accounting for 72% (157/217) of notifications (Figure 73). A large increase was observed in leptospirosis notifications from Queensland in the first part of 2011. Much of this increase appears to be associated with extensive flooding experienced in central and southern Queensland between December 2010 and January 2011.^114,115

Figure 73: Notifications of leptospirosis, Australia, 2006 to 2011, by month and year of diagnosis and state or territory

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Age and sex distribution

The median age of leptospirosis notifications was 43 years (range 4–79 years) and 91% (197/217) of cases were male. The highest notification rate was observed in the 55–59 year age group for males (Figure 74).

Figure 74: Notification rate for leptospirosis, Australia, 2011, by age group and sex (n=217)

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Typing information

The WHO/FAO/OIE Collaborating Centre for Reference and Research on Leptospirosis routinely conducts PCR-based serotyping for leptospirosis cases from Queensland (from whence the majority of cases are reported), and collates national data that may be submitted to the laboratory from other states or territories. These data may differ from that submitted to NNDSS. The WHO/FAO/OIE collaborating centre reported on 189 serotyped cases of leptospirosis nationally in 2011, of which 49% (93/189) were serovar Arborea, 10% (19/189) were Zanoni, 11% (22/189) were Australis, 14% (27/189) were Hardjo and the remainder were a range of serotypes, each representing 3% or fewer cases.

Typing information was available for 75% (163/217) of notifications to NNDSS, and of these, 46% were serovar Arborea.

Ornithosis

Ornithosis (or psittacosis) is caused by infection with the bacterium Chlamydophila psittaci and is transmitted to humans primarily from infected parrots of many species, but also poultry and a range of other birds.¹¹⁶ Transmission to humans can occur via the inhalation of contaminated dried faeces, nasal or eye secretions and dust from the feathers. Individuals at risk of contracting ornithosis include bird owners and those with occupational exposure to birds.¹¹⁷

Epidemiological situation in 2011

In 2011, there were 85 notifications of ornithosis (a rate of 0.4 per 100,000 population) compared with the 5-year mean of 96.8 notifications (2006 to 2010). The number of ornithosis notifications in 2011 was a 44% increase from 2010 (n=59), which was the lowest since 2001 (Figure 75).

Figure 75: Notifications of ornithosis, Australia, 2006 to 2011, by month and year of diagnosis and state or territory*

* No notifications from the Australian Capital Territory, the Northern Territory or South Australia in 2011.

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In 2011, there were notified cases of ornithosis in New South Wales, Queensland, Tasmania, Victoria and Western Australia. The majority of notifications in 2011 were from Victoria (68%, 58/85), where a significant increase in case numbers was reported compared with 2010 (n=36) and 2009 (n=40).¹¹⁸

Age and sex distribution

The median age of ornithosis notifications was 54 years (range 0–87 years) and 61% (52/85) of notified cases were male.

Q fever

Q fever is caused by infection with the bacterium, Coxiella burnetii. The primary reservoirs of these bacteria are cattle, sheep and goats. C. burnetii is resistant to environmental conditions and many common disinfectants.¹¹⁹ Q fever is most commonly transmitted via the airborne route, where the organism is carried in dust contaminated with tissue, birth fluids or excreta from infected animals.¹²⁰ Prior to the commencement of vaccination programs in Australia, approximately half of all cases in New South Wales, Queensland and Victoria were amongst abattoir workers.^121,122

The Australian Government funded the National Q Fever Management Program (NQFMP) between 2001 and 2006 for states and territories to provide free vaccine to at-risk groups (such as abattoir workers).¹²³

Adults at risk of Q fever infection, including abattoir workers, farmers, veterinarians, stockyard workers, shearers and animal transporters should be considered for vaccination. The administration of the Q fever vaccine requires a pre-vaccination screening test to exclude those recipients with a previous (unrecognised) exposure to the organism. A Q fever vaccine may cause an adverse reaction in a person who has already been exposed to the bacterium. Vaccination is not recommended for children under 15 years of age.⁴⁴

Epidemiological situation in 2011

In 2011, there were 338 notifications of Q fever (a rate of 1.5 per 100,000), compared with the 5-year mean of 375.2 notifications (2006–2010).

Between 1991 and 2001, and prior to the introduction of the NQFMP, Q fever notification rates ranged from between 2.5 and 4.9 per 100,000.¹²⁴ In 2011, the highest notification rates were from Queensland (3.6 per 100,000, n=164) and New South Wales (1.8 per 100,000, n=131). Cases also occurred in Victoria (n=24), Western Australia (n=10) and South Australia (n=7). There was 1 notification each from the Australian Capital Territory and the Northern Territory and none from Tasmania (Figure 76).

Figure 76: Notifications of Q fever, Australia, 2006 to 2011, by month and year of diagnosis and state or territory*

* No notifications from Tasmania in 2011.

Text version of Figure 76 (TXT 1 KB)

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Age and sex distribution

The median age of Q fever notifications was 45 years (range 3–88 years) and 74% of cases (249/338) were male. The highest notification rate was observed in the 40–44 year age group for males (Figure 77).

Figure 77: Notification rate for Q fever, Australia, 2011, by age group and sex (n=338)

Text version of Figure 77 (TXT 1 KB)

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Tularaemia

Tularaemia is caused by infection with the bacterium Francisella tularensis. The most common modes of transmission are through arthropod bites, handling infected animals, inhalation of infectious aerosols or exposure to contaminated food or water. Small mammals such as rodents, rabbits and hares are often the reservoir.¹²⁵

Epidemiological situation in 2011

In 2011, there were 2 notifications of tularaemia, both from Tasmania with exposure to sick or injured wildlife. This is the first time that F. tularensis type B had been detected in the Southern Hemisphere.¹²⁶ Both cases were in women who had been bitten by possums along the same stretch of road in a remote location, one in February and one in September 2011.¹²⁷

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Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2011 and classified as ‘other bacterial infections’ in the NNDSS. A total of 1,928 notifications were included in this group in 2011, which accounted for less than 1% of all the notifications to NNDSS, an increase in cases and a similar proportion as notified in 2010 (n=1,852 and 1% of total).

Legionellosis

Legionellosis, caused by the bacterium Legionella, can take the form of either Legionnaires’ disease, a severe form of infection of the lungs or Pontiac fever, a milder influenza-like illness. The species that are most commonly associated with human disease in Australia are L. pneumophila and L. longbeachae. Legionella bacteria are found naturally in low levels in the environment. In the absence of effective environmental treatment Legionella organisms can breed to high numbers in air conditioning cooling towers, hot water systems, showerheads, spa pools, fountains or potting mix.

Epidemiological situation in 2011

In 2011, there were 348 notifications of legionellosis, representing a rate of 1.5 per 100,000. Compared with the previous reporting period the overall number of legionellosis cases increased in 2011 by 16%. This number of annual notifications was the highest since 2006 (Figure 78).

Figure 78: Notifications of legionellosis, Australia, 2006 to 2011, by species

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Data on the causative species were available for 95% (n=332) of cases reported in 2011. Of the cases with a reported species there were roughly equal proportions of Legionella longbeachae (n=167) and L. pneumophila (n=164) (Table 18). A single case was reported with an infective species of L. bozemanii.

Table 18: Notifications of legionellosis, Australia, 2011, by species and state or territory

	State or territory
Species	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Australia
* 4 deaths. † 4 deaths.
L. longbeachae	0	32	3	20	30	5	12	65	167*
L. pneumophila	0	59	2	23	10	2	55	13	164†
L. bozemanii	0	0	0	0	0	0	1	0	1
Unknown species	4	4	0	2	0	0	6	0	16
Total	4	95	5	45	40	7	74	78	348
Rate (per 100,000)	1.1	1.3	2.2	1.0	2.4	1.4	1.3	3.3	1.5

Over the period 2006 to 2011, annual notifications of L. longbeachae ranged from 136 to 181 cases, while annual notifications of L. pneumophila ranged from 100 to 164 cases (Figure 78). Annual notifications of L. pneumophila have steadily increased since 2008.

Mortality data were available for 62% of notifications in 2011. There were 8 reported deaths due to legionellosis, which was an increase on the 7 deaths reported in 2010. Half of the deaths were associated with L. pneumophila infection and the remaining half was associated with L. longbeachae (Table 18). Mortality data should be interpreted with caution given the large proportion of cases reported without death data to the NNDSS.

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Geographical distribution

Jurisdictional-specific rates of legionellosis in 2011 varied from 1.0 per 100,000 in Queensland to 3.3 per 100,000 in Western Australia (Table 18).

Unlike the previous 3 years, the geographic distribution of L. longbeachae and L. pneumophila in 2011 aligned with longer historical trends.¹²⁴ L. longbeachae made up the majority of notifications in South Australia and Western Australia, while L. pneumophila was the most common infecting species in the eastern states (New South Wales, Queensland and Victoria).

Age and sex distribution

In 2011, legionellosis was predominantly seen in older males. Males accounted for the majority (67%) of the notifications of legionellosis resulting in a male to female ratio of 2:1. Overall, the age group with the highest notification rate was the 75–79 year age group (7 per 100,000). The highest age and sex specific rates were observed in men aged 75–79 years (11.5 per 100,000 population) and women aged 65–69 years (3.5 per 100,000, n=10) (Figure 79). The 8 cases that were reported to have died due to legionellosis ranged in age between 58 and 95 years (median 77 years); 7 deaths were males and 1 death was a female.

Figure 79: Notification rate for legionellosis, Australia, 2011, by age group and sex

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An infecting species analysis by age group shows that 91% of L. longbeachae notifications were reported in persons 40 years or over and is most predominant in the 75–79 year age group (3.6 per 100,000). Similarly 90% of L. pneumophila infections notified were in persons aged 40 years or over and is most predominant in the 80–84 year age group (3.6 per 100,000).

Seasonality

In 2011, diagnoses of legionellosis were highest in April and December, with 43 cases notified in each month (Figure 80). L. pneumophila occurred most frequently in the autumn months, with 58 cases reported over the months March to May 2011. L. longbeachae cases peaked in spring 2011, with 47 cases reported over the months September to November 2011, the majority (n=20) of which occurred in October. These patterns seen in 2011 are consistent with peaks in notifications experienced in previous years.

Figure 80: Notifications of legionellosis, Australia, 2007 to 2011, by month of diagnosis and species

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Place of acquisition

Place of acquisition was reported for 68% (n=235) of legionellosis cases notified in 2011. Of cases with a place of acquisition reported, most (n=218, 93%) were reported as having been acquired within Australia. A small number (n=17) of cases was reported as acquired overseas. Indonesia (n=9) and China (n=3) were the most commonly reported overseas place of acquisition.

Leprosy

Leprosy is a chronic infection of the skin and peripheral nerves due to the bacterium Mycobacterium leprae. Leprosy is a rare disease in Australia. Its incidence world-wide is declining due to factors including economic development, the use of Bacillus Calmette–Guérin vaccine and high coverage of multi-drug therapy. ¹⁴

Epidemiological situation in 2011

There were 8 notifications of leprosy in 2011, representing a rate of less than 0.1 per 100,000. All cases of leprosy reported in 2011 were reported as non-Indigenous (Figure 81).

Figure 81: Notifications of leprosy, Australia, 1992 to 2011, by year of diagnosis and Indigenous status

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Compared with the previous reporting period the number of leprosy cases decreased in 2011 by a third, from the 12 cases reported in 2010. Since 1992 annual notifications of leprosy ranged from 4 to 23 cases.

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Geographical distribution

In 2011, cases of leprosy were notified in New South Wales (n=3), Victoria (n=3), South Australia (n=1) and Western Australia (n=1).

Age and sex distribution

In 2011, notified cases of leprosy were predominantly seen in males, with a male to female ratio of 3:1. The median age of cases was 31 years (range 22–65).

Meningococcal disease (invasive)

Meningococcal disease is caused by the bacterium Neisseria meningiditis and becomes invasive when bacteria enter a normally sterile site, usually the blood (septicaemia), cerebrospinal fluid (meningitis) or both. The bacterium is carried by about 10% of the population without causing disease, and is transmitted via respiratory droplets. It occasionally causes a rapidly progressive serious illness, most commonly in previously healthy children and young adults. There are 13 known serogroups of meningococcus. Globally, serogroups A, B, C, W135 and Y most commonly cause disease.¹⁴ Historically, N. meningitidis serogroups B and C have been the major cause of invasive meningococcal disease (IMD) in Australia.

Epidemiological situation in 2011

In 2011, there were 241 notifications of IMD representing a rate of 1.1 per 100,000. While case numbers were 5% higher compared with 2010, they continue the downward trend in overall case numbers and were below the 5-year mean of 279 cases (Figure 82).

Figure 82: Notifications of invasive meningococcal disease, Australia, 2000 to 2011

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Data on serogroup were available for 90% of cases in 2011. Of these, 76% were caused by serogroup B organisms, 5% each by serogroup W135 and serogroup Y and 4% by serogroup C. Notifications of IMD caused by serogroup C organisms have decreased substantially following the introduction of the National Meningococcal C Vaccination Program in 2003, with less than 25 cases reported annually since 2006.

Mortality data were available for 56% of cases reported to the NNDSS in 2011. Of these, 15 were reported as having died from IMD, including 12 due to serogroup B, 2 due to serogroup Y and 1 due to serogroup W135 (Table 19). Mortality data should be interpreted with caution given the large proportion of cases reported without death data to the NNDSS.

Table 19: Deaths due to invasive meningococcal disease, Australia, 2011, by serogroup and state or territory

	State or territory
Serogroup	ACT	NSW	NT	Qld	SA	Tas.	Vic.	WA	Australia
B	0	4	0	2	2	0	2	2	12
C	0	0	0	0	0	0	0	0	0
W135	0	0	0	0	0	1	0	0	1
Y	0	0	0	1	0	0	1	0	2
Unknown	0	0	0	0	0	0	0	0	0
Total	0	4	0	3	2	1	3	2	15

Geographical distribution

Cases were reported from all states and territories, ranging from 2 cases in the Australian Capital Territory to 72 cases in New South Wales (Table 20). Jurisdictional-specific rates ranged from 0.5 per 100,000 in Australian Capital Territory to 2.0 per 100,000 in Tasmania.

Table 20: Notifications of invasive meningococcal disease, Australia, 2011, by serogroup and state or territory

	State or territory
Serogroup	ACT	NSW	NT	Qld	SA	Tas.	Vic.	WA	Australia
B	2	44	3	49	18	6	43	19	184
C	0	2	0	3	2	1	1	0	9
W135	0	4	0	2	1	3	2	0	12
Y	0	4	0	3	0	0	3	2	12
Unknown	0	18	1	4	0	0	1	0	24
Total	2	72	4	61	21	10	50	21	241
Rate (per 100,000)	0.5	1.0	1.7	1.3	1.3	2.0	0.9	0.9	1.1

Age and sex distribution

In 2011, sex was evenly distributed with a male female ratio of 1:1; however age specific variations did occur. This was particularly the case in the 0–4 year age group where the male to female ratio was at 1.8:1 and in the 10–14 year age group where it was 4.5:1.

The majority of cases reported (69%) were less than 25 years of age. Of those, the highest proportion (30%) and age specific rate, at 5 per 100,000, were cases less than 5 years of age. High rates also occurred amongst the 15–19 year age group (2.8 per 100,000) followed by the 20–24 year age group (1.6 per 100,000) (Figure 83).

Figure 83: Notification rate for invasive meningococcal disease, Australia, 2011, by age and sex

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Serogroup B accounted for the majority of cases across all age groups including those less than 25 years of age, where it accounted for 84% of cases. While rates of serogroup B infection remain high compared with the other serogroups, they continue to trend downwards. This was noted in 2011 for the 0–4 year age group where the rate of 4.0 per 100,000 represents a 43% decline from 2006 when the rate was 7.0 per 100,000 (Figure 84).

Figure 84: Notification rate for serogroup B invasive meningococcal disease, Australia, 2006 to 2011, by select age group

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There were no reported cases of IMD due to serogroup C amongst children and adolescents less than 20 years of age in 2011 and rates continue to be low, at less than 0.2 per 100,000 across all age groups (Figure 85).

Figure 85: Notification rate for serogroup C invasive meningococcal disease, Australia, 2006 to 2011, by select age group

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Seasonality

In 2011, diagnoses of IMD were highest across the winter months. This was consistent with the normal seasonal pattern of this disease (Figure 86).

Figure 86: Notifications of invasive meningococcal disease, Australia, 2006 to 2011, by serogroup and month and year of diagnosis

Text version of Figure 86 (TXT 1 KB)

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Vaccination status

Of the 9 cases of IMD due to serogroup C only 1 case was less than 24 years of age (and therefore eligible for vaccination) and this case was reported as not vaccinated.

Laboratory based meningococcal disease surveillance

The Australian Meningococcal Surveillance Programme (AMSP) was established in 1994 for the purpose of monitoring and analysing isolates of N. meningitidis from cases of IMD in Australia. The program is undertaken by a network of reference laboratories in each state and territory, using standardised methodology to determine the phenotype (serogroup, serotype and serosubtype) and the susceptibility of N. meningitidis to a core group of antibiotics. Annual reports of the AMSP are published in CDI with the latest report published for 2012.¹²⁸

Tuberculosis

Tuberculosis (TB) is an infection caused by the bacterium Mycobacterium tuberculosis. TB is transmitted by airborne droplets produced by people with pulmonary or respiratory tract TB during coughing or sneezing. While Australia has one of the lowest rates of tuberculosis in the world, the disease remains a public health issue in overseas-born and Indigenous communities.

Epidemiological situation in 2011

In 2011, there were 1,331 notifications of TB, a small increase (1%) on the number of cases reported in the previous year (n=1,312). While the substantial decline in the rate of TB since the 1960s has been maintained, notifications in the last decade tend to have increased (Figure 87).

Figure 87: Notification rate for tuberculosis, Australia, 1960 to 2011

Text version of Figure 87 (TXT 1 KB)

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At the time the annual report snap shot was agreed, the New South Wales TB data was affected by a data quality issue, resulting in an undercount of the number of TB cases in New South Wales and consequently nationally. The issue was identified and subsequently resolved in the NNDSS. For the revised case totals please refer to the NNDSS data on the Department of Health’s web site (www.health.gov.au/nndssdata). The analysis presented in this report relates to data agreed in the creation of the snap shot.

Geographical distribution

New South Wales (n=470), Victoria (n=371) and Queensland (n=223) accounted for 80% of all cases of TB diagnosed in Australia. Notification rates were highest in the Northern Territory (14.3 per 100,000), Victoria (6.6 per 100,000) and New South Wales (6.4 per 100,000). Rates in the remaining jurisdictions were all lower than the national notification rate of 5.9 per 100,000.

Age and sex distribution

In 2011, TB was predominantly seen in young adults and older males. Males accounted for more than half (56%) of the notifications of TB, resulting in a male to female ratio of 1.3:1. Overall, the age group with the highest notification rate was the 25–29 year age group (15.8 per 100,000). The highest age and sex specific rates were observed in men aged 85 years or over (20.5 per 100,000) and in women aged 25–29 years (15.4 per 100,000) (Figure 88).

Figure 88: Notification rate for tuberculosis, Australia, 2011, by age group and sex

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Enhanced surveillance

Enhanced data is collected on all cases of TB. These data were not finalised at the time core notification data were finalised for this report. Further analyses, including identification of risk groups and reporting on treatment outcomes, can be found in the TB annual report series, which is published in CDI.

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Acknowledgements

The authors wish to thank the following people for their contribution to this report.

Rachael Corvisy, Office of Health Protection

Members of the National Surveillance Committee

The National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, in particular, Clayton Chiu, Aditi Dey, Deepika Mahajan, Robert Menzies, and Helen Quinn

Author details

Coordinating author: Rachael Corvisy

Data management: Mark Trungove

Bloodborne diseases: Amy Bright

Gastrointestinal diseases: Rachael Corvisy, Gerard Fitzsimmons

Quarantinable diseases: Katrina Knope

Sexually transmissible infections: Amy Bright

Vaccine preventable diseases: Nicolee Martin, Kellie Gavin, Christina Bareja

Vectorborne diseases: Katrina Knope

Zoonoses: Timothy Sloan-Gardner, Katrina Knope

Other bacterial infections: Nicolee Martin, Christina Bareja

With contributions from:

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National organisations

Communicable Diseases Network Australia and subcommittees

Australian Childhood Immunisation Register

Australian Gonococcal Surveillance Programme

Australian Meningococcal Surveillance Programme

Australian Sentinel Practice Research Network

Australian Quarantine Inspection Service

The Kirby Institute

National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases

National Enteric Pathogens Surveillance Scheme

OzFoodNet Working Group

World Health Organization Collaborating Centre for Reference and Research on Influenza

State and territory health departments

Communicable Diseases Control, ACT Health, Australian Capital Territory

Communicable Diseases Surveillance and Control Unit, NSW Ministry of Health, New South Wales

Centre for Disease Control, Northern Territory Department of Health and Community Services, Northern Territory

Communicable Diseases Branch, Queensland Health, Queensland

Communicable Disease Control, South Australian Department of Health, South Australia

Communicable Diseases Prevention Unit, Department of Health and Human Services, Tasmania

Health Protection Branch, Department of Health, Victoria

Communicable Diseases Control Directorate, Department of Health, Western Australia

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Abbreviations

7vPCV

7 valent pneumococcal conjugate vaccine

13vPCV

13 valent pneumococcal conjugate vaccine

23vPPV

23 valent pneumococcal polysaccharide vaccine

ABLV

Australian bat lyssavirus

AFP

acute flaccid paralysis

AGSP

Australian Gonococcal Surveillance Programme

AIDS

acquired immunodeficiency syndrome

AMSP

Australian Meningococcal Surveillance Programme

ANCJDR

Australian National Creutzfeldt-Jakob Disease Registry

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ATAGI

Australian Technical Advisory Group on Immunisation

BFV

Barmah Forest virus

CDI

Communicable Diseases Intelligence

CDNA

Communicable Diseases Network Australia

CDWG

Case Definitions Working Group

CJD

Creutzfeldt-Jakob disease

COB

Country of birth

CRS

congenital rubella syndrome

DENV

dengue virus

Hib

Haemophilus influenzae type b

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HIV

human immunodeficiency virus

HPAIH

highly pathogenic avian influenza in humans

HRIG

human rabies immunoglobulin

HUS

haemolytic uraemic syndrome

IMD

invasive meningococcal disease

IPD

invasive pneumococcal disease

JEV

Japanese encephalitis virus

KUNV

Kunjin virus

MMR

measles-mumps-rubella

MVEV

Murray Valley encephalitis virus

NAI

Neuraminidase inhibition

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NAMAC

National Arbovirus and Malaria Advisory Committee

NDP

no data provided

NEC

not elsewhere classified

NIP

National Immunisation Program

NN

not notifiable

NNDSS

National Notifiable Diseases Surveillance System

NQFMP

National Q Fever Management Program

NSC

National Surveillance Committee

PCR

polymerase chain reaction

RRV

Ross River virus

RVC

Regional Verification Commission

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SARS

severe acute respiratory syndrome

STEC

Shiga toxin-producing Escherichia coli

STI(s)

sexually transmissible infections(s)

TB

tuberculosis

TSI

Torres Strait Islander

VPD(s)

vaccine preventable disease(s)

VTEC

verotoxigenic Escherichia coli

VZV

varicella zoster virus

WHO

World Health Organization

WHOCC

World Health Organization Collaborating Center

YFV

yellow fever virus