In just one week, the number of West Nile virus cases in the U.S. has increased by 40 percent with more deaths and infections on the way. According to the Associated Press, 1,590 cases of West Nile have been reported to the CDC this year, with 66 deaths.
Two weeks ago, there were only 693 documented cases in the U.S. with 26 dead. Dr. Lyle Petersen of the CDC told the AP that this year “we think the numbers may come close” to the outbreaks of 2002 and 2003, in which nearly 3,000 severe illnesses were reported, with 290 deaths.
Petersen said that about half of this year’s West Nile cases have been severe illnesses, but several factors complicate West Nile tracking, including the fact that most people infected by the virus show only mild symptoms or none at all. The disease also has a two-week incubation period between the actual infective bite of a West Nile-carrying mosquito and the onset of symptoms.
In a typical season, cases peak in mid-August then taper off, continuing through October. This year’s case numbers, however, seem to just keep rising.
In patients, West Nile can manifest in its less severe form, West Nile fever, or as a more serious neuro-invasive illness like meningitis, which is inflammation of the tissue around the brain and spinal cord, or encephalitis, inflammation of the brain itself.
The CDC says that 80 percent of patients show no symptoms at all, but those who do can experience fever, head and body aches, nausea, swollen glands and sometimes a rash on on the chest, stomach and back. More severe symptoms can include neck pain, vision loss, numbness vomiting, seizures, paralysis and coma.
The virus is mostly dangerous to the very young and the very old, as well as people who are immune-suppressed or have underlying health conditions. The CDC warns, however, that healthy people can still develop symptoms.
West Nile has been identified this year in all of the states except Alaska and Hawaii, but Texas has been the hardest hit. Last week, Dallas Mayor Mike Rawlings (D) ordered aerial pesticide spraying for all of the greater Dallas County area in an effort to kill the mosquitos that carry the disease.
The virus was first identified in the U.S. in 1999. It’s carried by birds and small rodents, but is transmissible to humans through mosquito bites. Scientists are reluctant to attribute this year’s severe and rapidly growing outbreak to the warm winter months and early spring or any other single factor, but they do concede that climate change may play a role in the current prevalence of the disease.
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