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West Nile Virus Infection Symptoms

Medical Author: Charles P. Davis, MD, PhD
Medical Editor: Melissa Conrad Stöppler, MD

West Nile Virus has reached epidemic levels in Texas in 2012. Many other states (43 as of August, 2012) also reported infections, and many report an increase in the number of people diagnosed with the disease. The US CDC considers this to be the largest outbreak in the U.S. since 2004. The disease is caused by a virus that is transmitted by a mosquito vector when the "mosquito bites" (injects a mouth part into human skin to obtain a blood meal) a human host. As of August 17, about 230 people have been diagnosed with the disease, and 10 have died in Texas. In the first time in about 45 years, health officials in Texas have launched airplanes to spray insecticide that kills mosquitoes to slow or halt this epidemic in the Dallas region.

Signs and symptoms of the West Nile virus infection range from no symptoms at all, to a rapidly fatal brain infection (encephalitis). In areas where the virus is common (Texas, in 2012, has had about 50% of all the incidences of infection in the U.S.), about 80% of people infected are more likely to show no symptoms of the infection or have only a mild, flulike illness rather than a severe brain infection. Even in an area of outbreak or epidemic, the likelihood of a person developing the more severe symptoms after infection with West Nile virus varies from 1 in 100-300 people.

The following are the symptoms to be aware of about 3 to 14 days after an infected mosquito bites a person and transmits the West Nile virus:

  • West Nile virus infection typically begins with the abrupt onset of fever, chills, muscle aches, headache, and overall feeling of illness. Headache is particularly common and may be severe. The person may have sensitivity to light with pain behind the eyes.
  • Most people fully recover. In others, particularly the elderly and some young children, the disease can progress to cause encephalitis or meningitis and infrequently, death.

Prevention of mosquito bites is key to avoiding infection with West Nile virus. The CDC recommends the following:

If a person develops any of the symptoms described above about 3 to 14 days after mosquito bite(s) occur, they should seek medical care for diagnosis and treatment. Although there is no specific West Nile virus treatment or vaccine available for humans, medical management and treatment of the symptoms early on may reduce complications or the severity of the disease.

REFERENCES: West Nile Virus.

United States. Centers for Disease Control and Prevention. "West Nile Virus."

Last Editorial Review: 8/17/2012 6:31:44 PM

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