Physical distancing and non-respiratory notifiable diseases in the Northern Territory, March-May 2020.

ABSTRACT: Strict physical distancing measures and border controls have been introduced in the Northern Territory (NT), and across Australia, to reduce the spread of coronavirus disease 2019 (COVID-19). These measures have been associated with reduced incidence of other respiratory illnesses such as influenza. It is currently unclear what effect these measures have on non-respiratory communicable diseases. The incidence of notifiable non-respiratory communicable diseases within the NT, from 15 March to 15 May 2020, the period of most restrictive physical distancing, was monitored and is here compared with two control periods: (i) the 4 months immediately prior and (ii) the same two-month period from the preceding 5 years. During the study period, there was a decline in incidence of communicable enteric illnesses, particularly in shigellosis and rotavirus where person-to-person spread is the main transmission route. There was an increase in chlamydial conjunctivitis in areas with endemic trachoma, which is under further investigation. There was no observed increase in conditions associated with crowding, such as those related to group A streptococcal infection.

The first 2 months of COVID-19 contact tracing in the Northern Territory of Australia, March-April 2020.

The Northern Territory (NT) Centre for Disease Control (CDC) undertook contact tracing of all notified cases of coronavirus disease 2019 (COVID-19) within the Territory. There were 28 cases of COVID-19 notified in the NT between 1 March and 30 April 2020. In total 527 people were identified as close contacts over the same period; 493 were successfully contacted; 445 were located in the NT and were subsequently quarantined and monitored for disease symptoms daily for 14 days after contact with a confirmed COVID-19 case. Of these 445 close contacts, 4 tested positive for COVID-19 after developing symptoms; 2/46 contacts who were cruise ship passengers (4.3%, 95% CI 0.5-14.8%) and 2/51 household contacts (3.9%, 95% CI 0.5-13.5%). None of the 326 aircraft passengers or 4 healthcare workers who were being monitored in the NT as close contacts became cases.

An outbreak of Salmonella Saintpaul gastroenteritis after attending a school camp in the Northern Territory, Australia.

An outbreak of salmonellosis occurred following attendance at a school camp between 5 and 8 August 2014 in a remote area of the Northern Territory, Australia. We conducted a retrospective cohort study via telephone interviews, using a structured questionnaire that recorded symptoms and exposures to foods and activities during the camp. A case was anyone with laboratory confirmed Salmonella Saintpaul infection or a clinically compatible illness after attending the camp. Environmental health officers from the Environmental Health Branch undertook an investigation and collected water and environmental samples. We interviewed 65 (97%) of the 67 people who attended the camp. There were 60 students and 7 adults. Of the 65 people interviewed, 30 became ill (attack rate 46%); all were students; and 4 had laboratory confirmed S. Saintpaul infection. The most commonly reported symptoms were diarrhoea (100% 30/30), abdominal pain (93% 28/30), nausea (93% 28/30) and fever (70% 21/30). Thirteen people sought medical attention but none required hospitalisation. Illness was significantly associated with drinking cordial at lunch on 7 August (RR 3.8, 95% CI 1.3-11, P < 0.01), as well as drinking cordial at lunch on 8 August (RR 2.1, 95% CI 1.1-4.2, P=0.01). Salmonella spp. was not detected in water samples or wallaby faeces collected from the camp ground. The epidemiological investigation suggests the outbreak was caused by environmental contamination of food or drink and could have occurred during ice preparation or storage, preparation of the cordial or from inadequate sanitising of the cooler from which the cordial was served. This outbreak highlights the risks of food or drink contamination with environmental Salmonella. Those preparing food and drink in campground settings should be vigilant with cleaning, handwashing and disinfection to prevent outbreaks of foodborne disease.

An outbreak of salmonellosis associated with duck prosciutto at a Northern Territory restaurant.

In June 2015, an outbreak of salmonellosis occurred among people who had eaten at a restaurant in Darwin, Northern Territory over 2 consecutive nights. We conducted a retrospective cohort study of diners who ate at the restaurant on 19 and 20 June 2015. Diners were telephoned and a questionnaire recorded symptoms and menu items consumed. An outbreak case was defined as anyone with laboratory confirmed Salmonella Typhimurium PT9 (STm9) or a clinically compatible illness after eating at the restaurant. Environmental health officers inspected the premises and collected food samples. We contacted 79/83 of the cohort (response rate 95%); 21 were cases (attack rate 27%), and 9 had laboratory confirmed STm9 infection. The most commonly reported symptoms were diarrhoea (100%), abdominal pain (95%), fever (95%) and nausea (95%). Fifteen people sought medical attention and 7 presented to hospital. The outbreak was most likely caused by consumption of duck prosciutto, which was consumed by all cases (OR 18.6, CI 3.0-∞, P < 0.01) and was prepared on site. Salmonella was not detected in any food samples but a standard plate count of 2 x 107 colony forming units per gram on samples of duck prosciutto demonstrated bacterial contamination. The restaurant used inappropriate methodology for curing the duck prosciutto. Restaurants should consider purchasing pre-made cured meats, or if preparing them on site, ensure that they adhere to safe methods of production.

Prevention of perinatal hepatitis B virus transmission: are we following guidelines?

It is recommended that infants born to women with hepatitis B infection should have serological review following completion of a four dose vaccination schedule. A review was undertaken on 102 neonates who received hepatitis B immunoglobulin to ascertain the proportion that were fully immunised and then followed up. Of the 66 infants for whom data were available, 65 (98.5%) had appropriately received four doses of hepatitis B vaccine in infancy and a further child had received three doses. Only 19/66 (29%; 95%CI: 18-41%) infants had documented follow-up serology results, one of whom was infected and one of whom was immune through clearance of infection. All children who had no serology documented were traced and offered testing in primary care. Our results demonstrate that although adherence to the vaccination schedule in this group of infants was good, mechanisms for ensuring that infants receive serology testing need to be strengthened.

The changing epidemiology of Murray Valley encephalitis in Australia: the 2011 outbreak and a review of the literature.

Murray Valley encephalitis virus (MVEV) is the most serious of the endemic arboviruses in Australia. It was responsible for six known large outbreaks of encephalitis in south-eastern Australia in the 1900s, with the last comprising 58 cases in 1974. Since then MVEV clinical cases have been largely confined to the western and central parts of northern Australia. In 2011, high-level MVEV activity occurred in south-eastern Australia for the first time since 1974, accompanied by unusually heavy seasonal MVEV activity in northern Australia. This resulted in 17 confirmed cases of MVEV disease across Australia. Record wet season rainfall was recorded in many areas of Australia in the summer and autumn of 2011. This was associated with significant flooding and increased numbers of the mosquito vector and subsequent MVEV activity. This paper documents the outbreak and adds to our knowledge about disease outcomes, epidemiology of disease and the link between the MVEV activity and environmental factors. Clinical and demographic information from the 17 reported cases was obtained. Cases or family members were interviewed about their activities and location during the incubation period. In contrast to outbreaks prior to 2000, the majority of cases were non-Aboriginal adults, and almost half (40%) of the cases acquired MVEV outside their area of residence. All but two cases occurred in areas of known MVEV activity. This outbreak continues to reflect a change in the demographic pattern of human cases of encephalitic MVEV over the last 20 years. In northern Australia, this is associated with the increasing numbers of non-Aboriginal workers and tourists living and travelling in endemic and epidemic areas, and also identifies an association with activities that lead to high mosquito exposure. This outbreak demonstrates that there is an ongoing risk of MVEV encephalitis to the heavily populated areas of south-eastern Australia.

Seroepidemiologic effects of influenza A(H1N1)pdm09 in Australia, New Zealand, and Singapore.

To estimate population attack rates of influenza A(H1N1)pdm2009 in the Southern Hemisphere during June-August 2009, we conducted several serologic studies. We pooled individual-level data from studies using hemagglutination inhibition assays performed in Australia, New Zealand, and Singapore. We determined seropositive proportions (titer ≥40) for each study region by age-group and sex in pre- and postpandemic phases, as defined by jurisdictional notification data. After exclusions, the pooled database consisted of, 4,414 prepandemic assays and 7,715 postpandemic assays. In the prepandemic phase, older age groups showed greater seropositive proportions, with age-standardized, community-based proportions ranging from 3.5% in Singapore to 11.9% in New Zealand. In the postpandemic phase, seropositive proportions ranged from 17.5% in Singapore to 30.8% in New Zealand, with highest proportions seen in school-aged children. Pregnancy and residential care were associated with lower postpandemic seropositivity, whereas Aboriginal and Torres Strait Islander Australians and Pacific Peoples of New Zealand had greater postpandemic seropositivity.

Imported malaria in the Northern Territory, Australia--428 consecutive cases.

Malaria is a notifiable disease in Australia with an average of 600 notifications per year in returned travellers or newly arrived refugees, migrants and visitors. Although endemic disease has been eliminated from the tropical north of Australia, the region remains malaria receptive due to the presence of efficient mosquito vectors. This study analyses enhanced surveillance data collected by the Centre for Disease Control on all cases of malaria notified in the Northern Territory from 1 January 2000 to 31 December 2010. There were 428 malaria episodes notified that occurred in 391 individuals with a median age of 26 years. Of these, 71.4% were male, 40.5% were Australian nationals and 38.0% were prescribed chemoprophylaxis. Primary infection consisted of 196 (51.3%) cases of Plasmodium falciparum, 165 (43.2%) P. vivax, 2 (0.5%) P. ovale, 1 (0.3%) P. malariae and 18 were mixed infections. There were 46 episodes of relapsed infection. Residents of non-malarious countries were most likely to have acquired primary infection in East Timor (40.6%), Papua New Guinea (27.8%), Indonesia (18.7%) and Africa (6.4%). Primary infection was diagnosed after a median 19 days (interquartile range (IQR) 7-69) after arrival in Australia for cases of P. vivax compared with 4 days for P. falciparum (IQR 2-11). Screening protocols led to the diagnosis of 27.2% of cases. Eighty-seven per cent of patients were admitted to hospital at the time of their malaria diagnosis with median duration of 3 days (IQR 2-4) and one patient died. Resettlement of people from endemic countries, as well as military and civilian activities, influences the prevailing notification rates and Plasmodium species type.

West nile virus (Kunjin subtype) disease in the northern territory of Australia--a case of encephalitis and review of all reported cases.

West Nile virus Kunjin subtype (WNV/KUNV) is enzootic across the tropical north of Australia, with epizootic spread into other jurisdictions. The clinical spectrum of illness in humans is poorly described. We report a clinical case of WNV/KUNV encephalitis and performed a retrospective chart audit of all cases of WNV/KUNV notified in the Northern Territory from 1992 to 2010. Thirteen cases of WNV/KUNV disease were identified; case notes were available for 10 of these presentations. Six of these patients had confirmed infection and presented with neuroinvasive illness, whereas the other four suspect cases comprised three cases with arthralgia, myalgia, and/or rash and one case with fever alone. On the available evidence, WNV/KUNV is of lower virulence compared with the New York 1999 strain. Difficulties in serological diagnosis, especially when paired acute and convalescent sera are not available, may adversely impact the accuracy of the epidemiological and clinical understanding of this virus.

Acute post-streptococcal glomerulonephritis in the Northern Territory of Australia: a review of 16 years data and comparison with the literature.

Data relating to acute post-streptococcal glomerulonephritis (APSGN) from the notifiable diseases surveillance system in the Northern Territory of Australia was extracted and analyzed. Isolates of Streptococcus pyogenes from confirmed cases were emm sequence typed. From 1991 to July 2008, there were 415 confirmed cases and 23 probable cases of APSGN notified. Four hundred fifteen (94.7%) of these were Indigenous Australians and 428 (97.7%) were people living in remote or very remote locations. The median age of cases was 7 years (range 0-54). The incidence of confirmed cases was 12.5/100,000 person-years, with an incidence in Indigenous Australian children younger than 15 years of age of 94.3 cases/100,000 person-years. The overall rate ratio of confirmed cases in Indigenous Australians to non-Indigenous Australians was 53.6 (95% confidence interval 32.6-94.8). Outbreaks of disease across multiple communities occurred in 1995 (N = 68), 2000 (N = 55), and 2005 (N = 87 [confirmed cases]). Various emm types of S. pyogenes were isolated from cases of APSGN including some types not previously recognized to be nephritogenic. The widespread outbreak in 2005 was caused by emm55.0 S. pyogenes. Acute post-streptococcal glomerulonephritis continues to occur in remote Indigenous communities in Australia at rates comparable to or higher than those estimated in developing countries. Improvements in preventative and outbreak control strategies are needed.

Meningitis and a febrile vomiting illness caused by echovirus type 4, Northern Territory, Australia.

In July 2007, a cluster of meningitis cases caused by an echovirus 4 strain was detected in 1 indigenous community in the Top End of the Northern Territory of Australia. Illness was characterized by fever, vomiting, and headache. Over the next 4 months, additional cases of meningitis and the fever and vomiting syndrome emerged in other indigenous communities and subsequently in the major urban center of Darwin. We describe the epidemiology of 95 laboratory-confirmed meningitis cases and conclude that the epidemic fever and vomiting syndrome was caused by the same enterovirus. Nucleotide sequencing of the whole genome verified this enterovirus (AUS250G) as a strain of echovirus type 4. Viral protein 1 nucleotide sequencing demonstrated 96% homology with an echovirus 4 strain responsible for a large outbreak of meningitis in the Yanbian Prefecture of China in 1996.

Predictive indicators for Ross River virus infection in the Darwin area of tropical northern Australia, using long-term mosquito trapping data.

OBJECTIVES: To describe the epidemiology of Ross River virus (RRV) infection in the endemic Darwin region of tropical northern Australia and to develop a predictive model for RRV infections. METHODS: Analysis of laboratory confirmed cases of RRV infection between 01 January 1991 and 30 June 2006, together with climate, tidal and mosquito data collected weekly over the study period from 11 trap sites around Darwin. The epidemiology was described, correlations with various lag times were performed, followed by Poisson modelling to determine the best main effects model to predict RRV infection. RESULTS: Ross River virus infection was reported equally in males and females in 1256 people over the 15.5 years. Average annual incidence was 113/100 000 people. Infections peaked in the 30-34 age-group for both sexes. Correlations revealed strong associations between monthly RRV infections and climatic variables and also each of the four implicated mosquito species populations. Three models were created to identify the best predictors of RRV infections for the Darwin area. The climate-only model included total rainfall, average daily minimum temperature and maximum tide. This model explained 44.3% deviance. Using vector-only variables, the best fit was obtained with average monthly trap numbers of Culex annulirostris, Aedes phaecasiatus, Aedes notoscriptus and Aedes vigilax. This model explained 59.5% deviance. The best global model included rainfall, minimum temperature and three mosquito species. This model explained 63.5% deviance, and predicted disease accurately. CONCLUSIONS: We have produced a model that accurately predicts RRV infections throughout the year, in the Darwin region. Our model also indicates that predicted anthropogenic global climatic changes may result in an increase in RRV infections. Further research needs to target other high-risk areas elsewhere in tropical Australia to ascertain the best local climatic and vector predictive RRV infection models for each region. This methodology can also be tested for assessing utility of predictive models for other mosquito-borne diseases endemic to locations outside Australia.