The Delaware Division of Public Health (DPH) would like to alert the medical community of evidence of West Nile Virus (WNV) in Delaware. To date, there have been no confirmed cases in humans in Delaware this season. However, two cases have been confirmed in chickens as part of Delaware’s sentinel surveillance system. Additionally, seven wild birds have tested positive since July 8, 2012.
Approximately 80 percent of all people infected by WNV experience no symptoms. About 20 percent of those who become ill with WNV typically have mild symptoms. Less than 1 percent of humans infected with WNV develop more serious symptoms which can result in long term health effects or death. Infection should be considered in adults 50 years of age or older who have onset of unexplained encephalitis or meningitis in late summer or early fall. The local presence of WNV enzootic activity or other human cases of WNV infection should further raise the index of suspicion.
West Nile virus first appeared in Delaware birds and horses in 2000. Delaware’s first confirmed human case of West Nile virus occurred in 2002. In 2003, 17 human cases were confirmed, including two deaths. While there were no reported human cases in 2004, 2006, and 2009, two cases were confirmed in 2005 and one in 2007, 2008 and 2011.
The DPH Laboratory (DPHL) performs WNV testing for humans, birds and horses. Methods include antibody testing, as well as Polymerase Chain Reaction (PCR) and culture. In humans, the preferred specimen is cerebrospinal fluid (CSF). CSF should be collected within 8 days of illness onset, while serum specimens should be collected within 8-14 days of illness onset. False positive antibody results for WNV may occur in patients recently vaccinated for, or infected with, related flaviviruses (i.e., yellow fever, Japanese Encephalitis, dengue)
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