Avian influenza in Australia: a summary of 5 years of wild bird surveillance.

BACKGROUND: Avian influenza viruses (AIVs) are found worldwide in numerous bird species, causing significant disease in gallinaceous poultry and occasionally other species. Surveillance of wild bird reservoirs provides an opportunity to add to the understanding of the epidemiology of AIVs. METHODS: This study examined key findings from the National Avian Influenza Wild Bird Surveillance Program over a 5-year period (July 2007-June 2012), the main source of information on AIVs circulating in Australia. RESULTS: The overall proportion of birds that tested positive for influenza A via PCR was 1.9 ± 0.1%, with evidence of widespread exposure of Australian wild birds to most low pathogenic avian influenza (LPAI) subtypes (H1-13, H16). LPAI H5 subtypes were found to be dominant and widespread during this 5-year period. CONCLUSION: Given Australia's isolation, both geographically and ecologically, it is important for Australia not to assume that the epidemiology of AIV from other geographic regions applies here. Despite all previous highly pathogenic avian influenza outbreaks in Australian poultry being attributed to H7 subtypes, widespread detection of H5 subtypes in wild birds may represent an ongoing risk to the Australian poultry industry.

Survival of hendra virus in the environment: modelling the effect of temperature.

Hendra virus (HeV), a highly pathogenic zoonotic paramyxovirus recently emerged from bats, is a major concern to the horse industry in Australia. Previous research has shown that higher temperatures led to lower virus survival rates in the laboratory. We develop a model of survival of HeV in the environment as influenced by temperature. We used 20 years of daily temperature at six locations spanning the geographic range of reported HeV incidents to simulate the temporal and spatial impacts of temperature on HeV survival. At any location, simulated virus survival was greater in winter than in summer, and in any month of the year, survival was higher in higher latitudes. At any location, year-to-year variation in virus survival 24 h post-excretion was substantial and was as large as the difference between locations. Survival was higher in microhabitats with lower than ambient temperature, and when environmental exposure was shorter. The within-year pattern of virus survival mirrored the cumulative within-year occurrence of reported HeV cases, although there were no overall differences in survival in HeV case years and non-case years. The model examines the effect of temperature in isolation; actual virus survivability will reflect the effect of additional environmental factors.

Evaluating the effectiveness of early vaccination in the control and eradication of equine influenza--a modelling approach.

In August 2007, Australia which had previously been free of equine influenza, experienced a large outbreak that lasted approximately 4 months before it was eradicated. The outbreak required a significant national response by government and the horse industries. The main components of the response were movement controls, biosecurity measures, risk-based zoning and, subsequently, vaccination to contain the outbreak. Although not initially used, vaccination became a key element in the eradication program, with approximately 140000 horses vaccinated. Vaccination is recognised as a valuable tool for managing EI in endemically infected countries but there is little experience using it in situations where the objective is disease eradication. Vaccination was undoubtedly an important factor in 2007 as it enabled movements of some horses and associated industry activities to recommence. However, its contribution to containment and eradication is less clear. A premises-level equine influenza model, based on an epidemiological analysis of the 2007 outbreak, was developed to evaluate effectiveness of the mitigation strategies used and to investigate whether vaccination, if applied earlier, would have had an effect on the course of the outbreak. The results indicate that early use of strategic vaccination could have significantly reduced the size of the outbreak. The four vaccination strategies evaluated had, by 1 month into the control program, reduced the number of new infections on average by 60% and the size of the infected area by 8-9%. If resources are limited, a 1 km suppressive ring vaccination around infected premises gave the best results, but with greater vaccination capacity, a 3 km ring vaccination was the most effective strategy. The findings suggest that as well as reducing clinical and economic impacts, vaccination when used with biosecurity measures and movement controls could play an important role in the containment and eradication of equine influenza.

The impact of a monthly rest day on avian influenza virus isolation rates in retail live poultry markets in Hong Kong.

Retail live poultry markets (LPMs) may act as a reservoir of avian influenza viruses (AIV). In this study we test the hypothesis that a rest day in the LPMs where the stalls are completely emptied of poultry, cleansed, and restocked will reduce the isolation rates of avian influenza viruses. The isolation rate of H9N2 subtype viruses from chicken was significantly lower after the rest day than prior to it, indicating its impact in reducing transmission. In contrast, Newcastle disease virus (NDV) isolation rates appear unaffected by this intervention, possibly reflecting differences in herd immunity or virus transmission dynamics.

An update on avian influenza in Hong Kong 2002.

An outbreak of highly pathogenic avian influenza caused by multiple genotypes of H5N1 virus occurred in Hong Kong, commencing in January 2002. Infection in local chicken farms was preceded by the detection of virus in multiple retail markets and the main poultry wholesale market. The first case of this disease on a local farm was detected on February 1, 2002. By February 9, 2002, 15 farms were infected, and by late March a total of 22 infected farms had been identified. Three main clusters of infected farms were seen, suggesting multiple incursions of virus, and subsequent limited lateral spread to neighboring firms. Control of this disease has been effected through a combination of quarantine, tightening of biosecurity measures, and depopulation of infected and contact farms. About 950,000 birds have been destroyed. Vaccination using a killed H5 vaccine was introduced in April 2002 to farms in one zone where infection has persisted. None of the viruses isolated contained the internal genes found in the 1997 H5N1 virus.

Psychosocial effects of mastectomy: is it due to mastectomy or to the diagnosis of malignancy?

Twenty-three consecutive married and sexually active Chinese women treated for breast cancer were compared with a randomly selected group of 34 female patients suffering from different kinds of malignancies. A structured interview was used to study both groups. The breast cancer group were found to be less depressed and more emotionally stable than those suffering from other malignancies, suggesting that the diagnosis of malignancy was the more important factor in the psychosocial morbidity of these patients.