West Nile and Birds
Birds Carry West Nile Virus all Over North America
West Nile virus probably came to North America with a bird, and it's spreading. Mosquitoes are infected when they bite birds. Then they bite people.
In 1999, West Nile Virus appeared in New York. It was the first time the virus had been found in North America. Though it's not known exactly how West Nile virus came to the United States, it's thought that it came with a bird.
In the story of how West Nile spread to every part of North America since 1999, birds are key players. Many species of birds have been found to be infected with the virus, and as we all know, birds range widely and migrate long distances. Wherever they fly, the virus goes too. American Crows are hit hard by the infection, and many crows died in 1999 and subsequent years as the epidemic swept through crow families.
Crows became the sentinel bird for mapping the spread of West Nile virus. Where crows started dying, health officials tested them for the virus - and found it. It turns out however, that other birds with a wide range are more important in the yearly West Nile epidemic: in recent years, attention has centered largely on the American Robin.
Mosquitoes spread the virus from bird to bird, and it seems that American Robins are the favorite meal choice of mosquitoes. As well, robins don't die off in large numbers from the infection. Because they are repeatedly bitten by mosquitoes, and the virus continues to multiply and circulate in their blood, robins are a reservoir of West Nile virus that amplifies the disease in both the bird and the mosquito population throughout the spring and summer.
In the story of how humans become infected with West Nile, the mosquitoes are the key players. A recent publication from The Consortium for Conservation Medicine (PLoS Biol. 2006; 4(4):e82. Kilpatrick et al.) details how mosquitoes turn to feeding on humans when robins disperse in late summer - a change in mosquito feeding behavior that coincides with an annual rise in human cases of West Nile fever at that time.
Mosquito control will obviously help, and individuals can join in that effort by avoiding having pools and puddles of standing water on their property. West Nile virus is here to stay, however - we will never get rid of mosquitoes completely. The good news is that most cases of West Nile infection are extremely mild, so enjoy the birds and remember to wear a good insect repellent when you are outdoors and there are mosquitoes around.
Related content:
West Nile Neurological Threat.
