West Nile

Mosquitoes. That's right, mosquitoes. As creepy little transmitters of diseases such as the current Zika virus epidemic (linked with causing the birth defect microencephaly), West Nile virus, malaria, chikungunya, and dengue fever, mosquitoes kill over 1 million people every year according to the World Health Organization. This fascinating video from PBS shows how they suck your blood: I am using insect repellent this summer after watching that video!

Long time readers may have noticed that the subject of West Nile Virus (WNV) pops up periodically here (and here, here, here, here, here). It's more than a passing fancy. I was professionally involved in public health measures around West Nile after its introduction to the US in 1999 and have maintained an interest, even though flu occupies much (too much) of my time. WNV is a mosquito-borne flavivirus of birds that occasionally infects humans (in this sense it is like bird flu, although only in this sense; bird flu is not passed from birds to humans via mosquitoes). The resulting infection…

A fascinating paper in CDC's journal, Emerging Infectious Diseases has more details on a problem we first mentioned, on the basis of news reports, back in June. It's about a possible relationship between West Nile Virus infection and the mortgage crisis, but the paper also gives a dramatic example of how the physical, biological and social environment can affect disease patterns and risks in populations. Infection with West Nile Virus is primarily a disease of birds. It is transmitted from bird to bird by mosquito bites and the disease is maintained by the cycling between birds and mosquitoes…

Like most public health scientists I am fascinated by the complicated relationship between the environment and disease. You build a military base somewhere and sexually transmitted diseases follow. You build a dam in Egypt and urinary schistosomiasis, a chronic debilitating disease that also predisposes to bladder cancer, entrenches itself in an area because infected workers are attracted from far away endemic areas. They work and often urinate in the water, seeding the shallows of rivers and lakes with schistosome eggs. When the eggs get into the snails, they germinate, the schistosome…

You become infected with West Nile Virus (WNV) when a mosquito vector bites you. As the mosquito sucks your blood (the protein meal makes it possible for her to ovulate), she replaces some of it with her saliva. The virus is in the saliva and if it finds a suitable cell to infect, we're off to the races. If you are bitten by an uninfected mosquito you obviously can't get infected. But a new set of experiments in mice shows that having been previously bitten by the same species of mosquito markedly increases the chance and severity of infection with WNV in subsequent bites:. In their…