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West Nile Virus Infection Cases Reach Highest Level Since '99
By Matt Brown
"A total of 693 cases of West Nile virus disease in people, including 26 deaths, have been reported," says the CDC. "Of these, 406 (59 percent) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 287 (41 percent) were classified as non-neuroinvasive disease."
It's worth noting that not only is that case total the highest reported to the CDC since 1999, 80 percent of those cases come from only six states: Texas, Mississippi, Louisiana, Oklahoma, South Dakota and California. Moreover, almost half of all cases -- including nine deaths -- were reported from Texas, prompting one judge to declare a state of emergency in Dallas. In response, the state recently began spraying insecticide from crop-dusting planes in certain areas to kill WNV-infected mosquitoes.
- The current number of cases of West Nile virus (WNV) infection is the highest since the disease first was detected in the United States in 1999.
- Forty-three states have reported WNV infections in people, birds or mosquitoes, according to the CDC.
- Of the 693 human WNV cases confirmed, 26 deaths have been reported through Aug. 14.
Clinical Presentation Is Often Nonspecific
The most efficient diagnostic method is detection of IgM antibody to WNV in serum collected within eight to 14 days of illness onset or cerebrospinal fluid collected within eight days of illness onset. One caveat, however, is that serological tests for WNV cross-react with other closely related flaviviruses (e.g., Japanese encephalitis, St. Louis encephalitis, dengue).
CT is not useful in the diagnosis of severe WNV infection but can help exclude other etiologies of acute meningoencephalitis. Brain MRI is often normal but will sometimes display leptomeningeal enhancement or parenchymal signal changes. The CDC website offers more information about diagnostic testing, including instructions for submitting specimens for lab analysis.
Generally, mild WNV infections have good patient outcomes, but severe disease cases (i.e., West Nile encephalitis or meningitis) can be fatal. Roughly one in 150 people infected with WNV develop serious illness, with potential symptoms, including
- high fever,
- neck stiffness,
- muscle weakness,
- vision loss,
- numbness and
Unfortunately, no specific treatment is available for WNV infection. In severe cases, management consists of supportive care that often involves hospitalization, intravenous fluids, respiratory support and prevention of secondary infections.
Academy Has Tools to Help Answer Patients' Questions
Prevention Is Key to Avoiding Disease
"Prevention is the best, only way to avoid the disease," she said. "Also, people are advised not to touch dead birds. FPs may find it helpful to log into their state or local health departments to get specific information."
The CDC offers the following tips to prevent mosquito bites:
- when outdoors, use insect repellent containing an EPA-registered active ingredient;
- use insect repellent and wear long sleeves and pants when outside, or consider staying indoors;
- ensure screens on windows and doors are in good shape;
- empty standing water from flower pots, buckets and barrels;
- change the water in pet dishes frequently, and replace the water in bird baths weekly;
- drill holes in tire swings so water drains out; and
- empty children's wading pools and store them on their sides when not in use.
CDC: West Nile Virus: Information and Guidance for Clinicians