Surveillance is the organised monitoring of levels of virus activity, vector populations, infections in vertebrate hosts, human cases, weather, and other factors to detect or predict changes in the transmission dynamics of arboviruses. A sound surveillance program requires a thorough understanding of the biology, ecology and interactions of the vertebrate and mosquito hosts. The transmission of arboviruses depends on these interactions.
In NSW, the presence of arboviruses in the environment is achieved through surveillance of chicken flocks, trapping of mosquitoes for virus isolation, and by human case surveillance.
The emphasis of the chicken surveillance is on detecting the presence of flaviviruses (Murray Valley Encephalitis and Kunjin viruses) across northern, inland areas of NSW. Regularly during the arboviral season (November – April) chickens in the flocks are bled, and the samples are tested for antibodies to these flaviviruses.
The mosquito trapping program serves to identify species, density, age structure and virus infection rates which are critical for early predictive data for surveillance system.
The aim of the NSW Arbovirus Surveillance Program is to provide an early warning of Murray Valley Encephalitis virus and Kunjin in the state, in an effort to reduce the potential for human disease.
In NSW, mosquito trapping and monitoring is undertaken by the Institute for Clinical Pathology and Medical Research (ICPMR) on behalf of Health Protection NSW. Mosquito populations are routinely monitored at up to 30 locations across the State, through the months of November to April to detect unusual densities that may indicate increased arboviral activity. At inland monitoring locations, mosquitoes are also tested for the presence of both alphaviruses and flaviviruses.
NSW Health undertakes mosquito surveillance across NSW from November to April/May each year. In response to Japanese Encephalitis (JE) outbreak, NSW Heath expanded the mosquito surveillance network around infected piggeries and to areas where human cases were reported. The mosquito samples (including samples collected prior to JE outbreak) were tested for Japanese encephalitis virus (JEV).
*More recent samples have tested negative for JEV
In NSW, sentinel chicken surveillance is undertaken by the Institute for Clinical Pathology and Medical Research (ICPMR) on behalf of the Health Protection NSW. Sentinel chicken flocks located at inland locations are bled weekly during the mosquito season (November - April) to detect the transmission of Murray Valley Encephalitis virus and Kunjin virus.
NSW Health undertakes sentinel chicken surveillance in inland areas of NSW from December to April/May each year. The blood samples collected from the chicken flocks during the surveillance season were tested for Japanese encephalitis virus (JEV).
The NSW Arbovirus Surveillance and Mosquito Monitoring Program closed the season for 2021-22, with the week ending 14 May 2022. The start date of the 2022-23 season will be dependent on climatic conditions in Spring.
NSW Health, with support from the National Centre for Immunisation Research and Surveillance (NCIRS), recently conducted a time-limited serological (blood test) survey in 5 regional NSW towns. The purpose of this survey was to inform the public health response to Japanese encephalitis in NSW over the summer period 2022-23. The survey is now closed.