Researchers at the University of Texas Medical Branch at Galveston recently published an article showing that West Nile viral infection is exacerbated by earlier bites from uninfected mosquitoes. The experimenters acknowledge that these findings may seem a bit counter-intuitive in light of other infectious disease research. For example, with parasites or bacteria, usually prior exposure stimulates an immune response that can counter further attacks from that organism. With West Nile the scientists also hypothesize that early nonvirulent foreign mosquito saliva triggers an inflammatory response. However, in this case the influx of immune cells only provides more susceptible cells for the virus to infect.
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