Low seroprevalence of Murray Valley encephalitis and Kunjin viruses in an opportunistic serosurvey, Victoria 2011.

OBJECTIVE: To assess evidence of recent and past exposure to Murray Valley encephalitis virus (MVEV) and West Nile clade Kunjin virus (KUNV) in residents of the Murray Valley, Victoria, during a period of demonstrated activity of both viruses in early 2011. METHODS: A cross-sectional serosurvey using two convenience samples: stored serum specimens from a diagnostic laboratory in Mildura and blood donors from the Murray Valley region. Specimens were collected between April and July 2011. The main outcome measure was total antibody (IgM and IgG) reactivity against MVEV and KUNV measured using an enzyme immunoassay and defined as inhibiting binding of monoclonal antibodies by >50%, when compared to negative controls. Evidence of recent exposure was measured by the presence of MVEV and KUNV IgM detected by immunofluorescence. RESULTS: Of 1,115 specimens, 24 (2.2%, 95% CI 1.3-3.0%) were positive for MVEV total antibody, and all were negative for MVEV IgM. Of 1,116 specimens, 34 (3.1%, 95% CI 2.0-4.0%) were positive for KUNV total antibody, and 3 (0.27%) were KUNV IgM positive. Total antibody seroprevalence for both viruses was higher in residents born before 1974. CONCLUSIONS: Despite widespread MVEV and KUNV activity in early 2011, this study found that seroprevalence of antibodies to both viruses was low (<5%) and little evidence of recent exposure. IMPLICATIONS: Our findings suggest both viruses remain epizootic in the region and local residents remain potentially susceptible to future outbreaks.

The spread of influenza A(H1N1)pdm09 in Victorian school children in 2009: implications for revised pandemic planning.

BACKGROUND: Victoria was the first state in Australia to experience community transmission of influenza A(H1N1)pdm09. We undertook a descriptive epidemiological analysis of the first 1,000 notified cases to describe the epidemic associated with school children and explore implications for school closure and antiviral distribution policy in revised pandemic plans. METHODS: Records of the first 1,000 laboratory-confirmed cases of influenza A(H1N1)pdm09 notified to the Victorian Government Department of Health between 20 May and 5 June 2009 were extracted from the state's notifiable infectious diseases database. Descriptive analyses were conducted on case demographics, symptoms, case treatment, prophylaxis of contacts and distribution of cases in schools. RESULTS: Two-thirds of the first 1,000 cases were school-aged (5-17 years) with cases in 203 schools, particularly along the north and western peripheries of the metropolitan area. Cases in one school accounted for nearly 8% of all cases but the school was not closed until nine days after symptom onset of the first identified case. Amongst all cases, cough (85%) was the most commonly reported symptom followed by fever (68%) although this was significantly higher in primary school children (76%). The risk of hospitalisation was 2%. The median time between illness onset and notification of laboratory confirmation was four days, with only 10% of cases notified within two days of onset and thus eligible for oseltamivir treatment. Nearly 6,000 contacts were followed up for prophylaxis. CONCLUSIONS: With a generally mild clinical course and widespread transmission before its detection, limited and short-term school closures appeared to have minimal impact on influenza A(H1N1)pdm09 transmission. Antiviral treatment could rarely be delivered to cases within 48 hours of symptom onset. These scenarios and lessons learned from them need to be incorporated into revisions of pandemic plans.

Murray Valley encephalitis: a review of clinical features, diagnosis and treatment.

Murray Valley encephalitis virus (MVEV) is a mosquito-borne virus that is found across Australia, Papua New Guinea and Irian Jaya. MVEV is endemic to northern Australia and causes occasional outbreaks across south-eastern Australia. 2011 saw a dramatic increase in MVEV activity in endemic regions and the re-emergence of MVEV in south-eastern Australia. This followed significant regional flooding and increased numbers of the main mosquito vector, Culex annulirostris, and was evident from the widespread seroconversion of sentinel chickens, fatalities among horses and several cases in humans, resulting in at least three deaths. The last major outbreak in Australia was in 1974, during which 58 cases were identified and the mortality rate was about 20%. With the potential for a further outbreak of MVEV in the 2011-2012 summer and following autumn, we highlight the importance of this disease, its clinical characteristics and radiological and laboratory features. We present a suspected but unproven case of MVEV infection to illustrate some of the challenges in clinical management. It remains difficult to establish an early diagnosis of MVEV infection, and there is a lack of proven therapeutic options.

Contact tracing of in-flight measles exposures: lessons from an outbreak investigation and case series, Australia, 2010.

OBJECTIVE: To describe a 2010 outbreak of nine cases of measles in Australia possibly linked to an index case who travelled on an international flight from South Africa while infectious. METHODS: Three Australian state health departments, Victoria, Queensland and New South Wales, were responsible for the investigation and management of this outbreak, following Australian public health guidelines. RESULTS: An outbreak of measles occurred in Australia after an infectious case arrived on a 12-hour flight from South Africa. Only one of four cases in the first generation exposed to the index case en route was sitting within the two rows recommended for contact tracing in Australian and other guidelines. The remaining four cases in subsequent generations, including two health care workers, were acquired in health care settings. Seven cases were young adults. Delays in diagnosis and notification hampered disease control and contact tracing efforts. CONCLUSION: Review of current contact tracing guidelines following in-flight exposure to an infectious measles case is required. Alternative strategies could include expanding routine contact tracing beyond the two rows on either side of the case's row or expansion on a case-by-case basis depending on cabin layout and case and contact movements in flight. Releasing information about the incident by press release or providing generic information to everyone on the flight using e-mail or text messaging information obtained from the relevant airline, may also be worthy of consideration. Disease importation, inadequately vaccinated young adults and health care-related transmission remain challenges for measles control in an elimination era.

Public health response to imported case of poliomyelitis, Australia, 2007.

Australia, along with 36 other countries in the Western Pacific Region, was declared free of poliomyelitis by the World Health Organization in October 2000. Yet, the persistence of wild poliovirus in the 4 remaining polio-endemic countries-Afghanistan, India, Nigeria, and Pakistan-poses a risk for its importation into all countries declared polio free. We describe the public health response and outcomes resulting from the importation of a wild poliovirus infection in Melbourne, Australia, in July 2007. This response, based on an assessment of the risk for transmission, included offering vaccination with inactivated polio vaccine to the contacts and placing the index patient in isolation and the household contacts in quarantine until consecutive fecal specimens were negative for poliovirus by culture. The experience gained from the polio importation event in Australia may assist other polio-free countries to prepare for, and respond to, a similar event. No secondary clinical cases resulted from this importation.

Personal protective equipment and antiviral drug use during hospitalization for suspected avian or pandemic influenza.

For pandemic influenza planning, realistic estimates of personal protective equipment (PPE) and antiviral medication required for hospital healthcare workers (HCWs) are vital. In this simulation study, a patient with suspected avian or pandemic influenza (API) sought treatment at 9 Australian hospital emergency departments where patient-staff interactions during the first 6 hours of hospitalization were observed. Based on World Health Organization definitions and guidelines, the mean number of "close contacts" of the API patient was 12.3 (range 6-17; 85% HCWs); mean "exposures" were 19.3 (range 15-26). Overall, 20-25 PPE sets were required per patient, with variable HCW compliance for wearing these items (93% N95 masks, 77% gowns, 83% gloves, and 73% eye protection). Up to 41% of HCW close contacts would have qualified for postexposure antiviral prophylaxis. These data indicate that many current national stockpiles of PPE and antiviral medication are likely inadequate for a pandemic.

An outbreak of Barmah Forest virus disease in Victoria.

This report describes the epidemiological and clinical features of an outbreak of 47 cases of laboratory-confirmed Barmah Forest virus disease (BF disease) that occurred in Victoria between January and May 2002. Laboratory-confirmed cases were investigated, and information on travel history and clinical details was collected. Surveillance data from adult mosquito trappings and climatic conditions in the Wellington Shire were also reviewed. The response rate for interviews was 85 per cent (40/47). The most common symptoms reported by cases included arthralgia (95%), lethargy (90%) and maculopapular rash (72.5%). Transmission of BF disease in the Gippsland region was associated with unusually high numbers of Ochlerotatus camptorhynchus mosquitoes. This outbreak was of interest due to the fact that cases of BF disease outnumbered cases of Ross River virus disease (RR disease) in Victoria for the first time since data were available. Similar outbreaks of BF disease, in the absence of RR disease, occurred in Western Australia in 1993 and New South Wales in 1994/1995. Although the majority of BF disease cases reported regular outdoor activity during which they could be exposed to mosquito populations, they infrequently take precautions to limit exposure. Further efforts need to be made to educate people of the importance of using repellents and other personal preventative measures.