Introduction | What It Is and How It's Transmitted | Prevention | Humans and West Nile | Animals and West Nile | Research and Surveillance | Resources About West Nile Virus
Most people who are bitten by a mosquito infected with West Nile virus do not become ill.
No one is sure just how many people have been infected by the virus. In 2002, a total of 4,156 human cases of laboratory-confirmed West Nile virus Infections were reported by 39 states and the District of Columbia. Two hundred and eighty-four deaths were reported in the same period.
Courtesy of CDC.
The onset of illness ranged from June 10 to November 4, with the majority of cases occurring in August and September.
In 2003, the first human case of West Nile virus was confirmed July 7 in South Carolina. By Sept. 30, 2003, CDC had received reports of 5,722 human cases, including 110 deaths.
People who do become ill from West Nile virus generally develop symptoms three to 14 days after being bitten by an infected mosquito.
About one in 100 to 150 people infected with West Nile virus develop a severe, potentially fatal form of the disease. West Nile can cause serious neurological disease, including encephalitis, an inflammation of the brain, or meningitis, inflammation of the tissues that cover the brain and spinal cord. Encephalitis is most common in persons 50 years of age and older.
While there is no specific therapy available for infection with the West Nile virus, the severe form of the disease may require intensive supportive care and hospitalization.
Courtesy of CDC.
About 20 percent of people infected with the virus develop West Nile fever. Commonly described as a flu-like illness, West Nile fever may be more severe than many health officials originally believed.
| Symptoms of West Nile Virus meningoencephalitis may include: |
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Headache High fever Neck stiffness Stupor Disorientation Coma Tremors Convulsions Muscle weakness Paralysis | |
Mild cases of West Nile fever tend to go unreported. But, among persons who seek medical treatment for their illness, its impact seems to be greater than first thought.
Preliminary results from Chicago Department of Public Health interviews with 100 patients who had documented West Nile fever show that the illness lasts an average of more than a month.
Almost all (96%) reported fatigue lasting a median of 30 days; 61% reported muscle weakness lasting a median of 28 days; 71% had a headache for an average of 10 days; and 53% reported difficulty concentrating for a median of 14 days. Three-fourths missed work or school for an average of 10 days.
The long-term Impact of West Nile virus Is unknown. CDC issues daily updates on human cases and West Nile activity in mosquitoes, birds, and animals.
Introduction | What It Is and How It's Transmitted | Prevention | Humans and West Nile | Animals and West Nile | Research and Surveillance | Resources About West Nile Virus
Oct. 8, 2003
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