West Nile Virus a North American Fixture

CNN (Internet / TV) June 6, 2005

Within two years of West Nile's 1999 introduction to North America in New York, the virus was in Canada. The following year, horses in Mexico had it. "That's one of the real mysteries about Mexico, that there are very few documented human cases if any, and the virus has been there for three years," said Dr. Scott Weaver, director for tropical and emerging infectious diseases at the University of Texas Medical Branch. "We don't see evidence of people in Mexico developing neurological diseases like encephalitis at the same rate that they do in the United States, and we're really not sure why," said Weaver, whose research efforts in Mexico have tracked various forms of the disease in horses. "One theory is that people in Mexico are exposed to more related flavivirus, which is a different virus of the same genus, and there may be some cross protection when a person ... develops antibodies that protect them to some extent against West Nile infection."

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