West Nile – what is the actual risk?

Threatwatch is your early warning system for global dangers, from nuclear peril to deadly viral outbreaks. Debora MacKenzie highlights the threats to civilisation – and suggests solutions

The news this week is full of stories of West Nile virus, with Dallas, Texas declaring a health emergency and launching aerial insecticide spraying after 200 known cases and 10 deaths from West Nile this summer. But how much of a threat is the virus really? And could a minor bout of West Nile actually be your best protection for the coming years?

Anything that kills people, of course, is by definition a concern. What is most worrying about West Nile is that it appears to be on the rise – and virologists worry that this doesn't just mean more West Nile cases. It also means its nastier cousins, such as dengue, chikungunya and tick-borne encephalitis, could start booming as well.

West Nile virus normally infects birds, and is carried between them by mosquitoes. In temperate regions, the number of infected birds rises steadily after mosquitoes become active in spring. By late summer, so many birds have been infected that mosquito species that bite both birds and people occasionally carry the virus from a bird to a human. Horses are also severely affected.

Only one in five infected people develops any symptoms, and they are mostly flu-like. About one person in 150 – mostly the elderly or people with impaired immunity – develop serious, sometimes fatal, illness. Survivors of that may suffer kidney damage.

Read more: http://www.newscientist.com/article/dn22194-threatwatch-west-nile--what-is-the-actual-risk.html