Europe at risk of West Nile fever spread by mosquitoes, say experts

The potentially fatal West Nile fever (WNF) could be spread in Europe much more easily than previously thought, scientists are warning. The mosquito-borne disease, which can cause fatal inflammation of the brain, is usually found in birds. However, new hybrid mosquitoes are passing the disease on from birds to humans.

WNF is commonly spread between birds, which act as reservoir hosts, by mosquitoes that only bite birds, but hybrid mosquitoes that bite both birds and humans are allowing the disease to spread. WNF usually has mild symptoms in humans but can potentially lead to severe neurological problems, including meningitis, brain inflammation or even death. Now, with increased cases of WNF in Europe, researchers in Portugal are investigating these hybrids and assessing the risks posed to humans. The scientists studied mosquitoes collected from nearby a bird reserve and observed their offspring, up to fifteen per cent of which were born hybrids. Similar results were found in mosquitoes carrying WNF in the USA, which has experienced several human outbreaks in the last decade.

However, the research team believes that European populations, having been exposed to the disease over a longer period of time than the USA population, are at less risk of serious infection. Report author Bruno Gomes explains that “hybrids exist in relevant numbers in the South of Europe, and we need to be alert for the possibility that other WNF cases will emerge, but the severity of disease is predicted to be nowhere close to what has been seen in the US.”

For further information on the report contact Bruno Gomes at bsilva@ihmt.unl.pt

Published: Tuesday, 8th December 2009 by Tom Freeman

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