West Nile Virus Risk In The UK
In response to cases of West Nile virus (WNV) in northern Italy, the UK's Department for Environment, Food and Rural Affairs (DEFRA) has performed an assessment of the risk of WNV emerging in the UK.
Among their conclusions (with my comments in italics) are:
- There is a continuous low risk of WNV introduction from migratory wild birds.
- Introduction of WNV from legal trade in horses is very low. Really, it's zero since horses can't spread the virus.
- WNV would cause "some impact" on the UK horse industry because of illness and death, and movement of horses from affected holdings would be subject to controls. "Some impact" is presumably an understatement, considering what has happened in North America. Restricting movement of horses doesn't make sense because infected horses can't transmit the virus, so there would be no reason to restrict any horse movement.
- The potential for WNV becoming established in the UK is "very low". I don't know the details about mosquito populations in the UK, but I suspect this is understating the issue. When WNV first emerged in North America, it was often stated that it wouldn't survive the winter and would not be a problem in the next year. That turned out to be (very) wrong.
If we've learned one thing from WNV (and other emerging infectious diseases), it's that prediction of risks is very difficult. An understanding of the biology of the organism, its vectors and its hosts can be used to make logical assumptions, but we get fooled time and again by diseases that don't do what they're "supposed to do". Will WNV emerge as a problem in the UK? Probably. Given the potential for expansion of the range of this virus in Europe, potential effects of climate change and the inherent unpredictability of infectious diseases, it's more likely than not that WNV will reach the UK sometime in the future.
Image from http://www.ci.berkeley.ca.us/ContentDisplay.aspx?id=16144
