Why Is West Nile Becoming So Virulent In Australia?

West Nile Virus in Australia has typically been less potent than other strains of the virus found around the world. However, a more-potent strain began circulating there in 2011. WNV infections were confirmed in 1,000 horses and 10 percent of those infected died.

The original strain of West Nile in Australia was caused by Culex annulirostris mosquitoes found in the northern part of the country; it had originally been classified as a separate virus (the Kunjin virus), but was re-classified as a subtype of West Nile: WNVKUN.

It is not entirely clear why the more-virulent form of the disease happened, though researchers believe it most likely encompasses replication capacity and other environmental factors. To help narrow down what happened to the virus to make it more potent, researchers investigated the inflammatory response of cells to the virus.

Drs. Bixing Huang, Nic West, Jelena Vider, Ping Zhang, Rebecca Griffiths, Ernst Wolvetang, Peter Burtonclay and Warrilow infected cells with either the virulent strain of WNV or the strain that Australia used to have before 2011. The cell’s immune responses were then compared using two digital immune gene expression profiling systems, which allowed the scientists to compare the gene expression of 249 inflammation-associated genes.

The study team concluded that the NSW2012 isolate may have unique genetic characteristics that contributed to the outbreak, which is consistent with their hypotheses that the virulence of the disease is related to the inflammatory response. The scientists said both systems used in the study will be helpful in understanding the virus and will help detect emerging virulent viruses

find future applications in understanding virus pathogenicity, and ultimately for the establishment of early warning systems for the detection of virulent emerging viruses.

Read the study here.