Barmah Forest Virus Epidemic on the South Coast of New South Wales, Australia, 1994–1995: Viruses, Vectors, Human Cases, and Environmental Factors

Abstract

In 1995, the largest recorded outbreak of human disease resulting from infection with the mosquito transmitted alphavirus Barmah Forest (BF) virus occurred along the south coast of New South Wales, Australia. The virus was first isolated in early January from mosquitoes collected at Batemans Bay and predisposed the recognition of 135 human clinical cases. The cases of BF virus were identified initially from Batemans Bay during late January, and the majority (30%) of all cases came from this town. After 5 wk, all major centers on the south coast had clinical patients. Aedes vigilax (Skuse) were especially abundant at Batemans Bay, with levels up to 8 times greater than normal. This species yielded 111 isolates and appeared to be the major vector of BF virus. Attempts to examine if BF virus was maintained in the field by vertical transmission within Ae. vigilax populations were unsuccessful; no evidence of vertical transmission with BF virus, nor any other arbovirus, was found in > 17,000 adults emerging from field-collected larvae from the region following peak virus activity. In addition to BF virus, other viruses were recovered from field-collected adult mosquitoes, including Ross River (10 isolates), Edge Hill (21), and Stratford (10). Ae. vigilax again yielded the majority of these viral isolates. The BF virus outbreak appeared to be associated with several factors. A lack of recent BF virus activity in the region provided a highly susceptible human population, and unusual weather conditions of above average rainfall coupled with high tides resulted in extraordinarily large populations of Ae. vigilax.

Spatiotemporal variation of notified Barmah Forest virus infections in Queensland, Australia, 1993 – 2001

“…For example, in 1995, the largest recorded outbreak of human disease resulting from infection by BFv occurred along the south coast of New South Wales, Australia (Doggett et al 1999), when 135 cases of BFv were notified. The outbreak appeared to be associated with several factors.…”

Ross River Virus and Barmah Forest Virus Infections: A Review of History, Ecology, and Predictive Models, with Implications for Tropical Northern Australia

“…Although the first outbreak of BFV occurred during 1992 in the Northern Territory (Merianos et al 1992), subsequent outbreaks have been reported from southwest Western Australia in 1993(Lindsay et al 1995b, New South Wales in 1995 (Doggett et al 1999), and Victoria in 2002 (Passmore et al 2002). The 2005-2006 period marked the largest BFV epidemic on record in Australia, with 1,895 notifications (Liu et al 2006).…”

Wetlands and mosquitoes: a review

“…Muhar et al (2000) found that risk of Ross River virus in Brisbane, Australia was significantly related to several wetland habitats including intertidal and freshwater ones associated with floodplains. More recently, Barmah Forest virus has become a public health issue in Australia, with symptoms similar to Ross River virus and the two diseases have some mosquito vectors in common (Doggett et al 1999;Quinn et al 2005).…”