The CDC just published an article on the prevalence of West Nile Virus among the homeless in Houston, Texas. With a 6.8% prevalence rate in a population of 397, and a 16.4% seroprevalence rate in those homeless for more than a year, the homeless in Houston could be considered a high risk group. Participants were tested for HIV, Hep B and C, and WNV infections. Blood samples were collected and tested for WNV antibodies by igG ELISA and hemagglutination inhibition (HI) tests.
One interesting aspect of this study was the finding that marijuana use predicted WNV infection, which is difficult to explain. Some possible explanations proposed by the article included 1) this finding was due to chance, 2) people using marijuana spend more time outside between dusk and dawn and thus could be experiencing greater exposure to the Culex mosquito, 3) mosquitos could be attracted to marijuana smoke, or 4) marijuana use could affect cognition or slow a person's reaction to a mosquito drawing blood. This epidemiological study will help public health authorities determine appropriate intervention and prevention strategies.