West Nile Virus

Prevent Mosquito Bites

What is West Nile virus?
West Nile virus is an arthropod-borne virus (arbovirus) most commonly spread by infected mosquitoes. West Nile virus can cause febrile illness, encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord).

How do people get infected with West Nile virus?
Most people get infected with West Nile virus by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the virus to humans and other animals.

In a very small number of cases, West Nile virus has been spread through blood transfusions, organ transplants, and from mother to baby during pregnancy, delivery, or breastfeeding.

Who is at risk for infection with West Nile virus?
Anyone living in an area where West Nile virus is present in mosquitoes can get infected. West Nile virus has been detected in all lower 48 states (not in Hawaii or Alaska). Outbreaks have been occurring every summer since 1999. The risk of infection is highest for people who work outside or participate in outdoor activities because of greater exposure to mosquitoes.

How soon do people get sick after getting bitten by an infected mosquito?
The incubation period is usually 2 to 6 days after being bitten by an infected mosquito, but the beginning of sickness can range from 2 to 14 days. This period can be longer in people with certain medical conditions that affect the immune system.

What are the symptoms of West Nile virus disease?
Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.

About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.

Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent. About 10 percent of people who develop neurologic infection due to West Nile virus will die.

Who is at risk for serious illness if infected with West Nile virus?
People with certain medical conditions, such as cancer, diabetes, hypertension and kidney disease are at greater risk for serious illness.

What should I do if I think a family member might have West Nile virus disease?
Consult a healthcare provider for evaluation and diagnosis.

How is West Nile virus disease diagnosed?
Diagnosis is based on a combination of clinical signs and symptoms and specialized laboratory tests of blood or spinal fluid. These tests typically detect antibodies that the immune system makes against the viral infection.

What is the treatment for West Nile virus disease?
There are no medications to treat or vaccines to prevent West Nile virus infection. Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.
People with milder symptoms typically recover on their own, although some symptoms may last for several weeks.

In more severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

When do most cases of West Nile virus disease occur?
Most people are infected in the late summer to early fall months.

Where do most cases of West Nile virus disease occur?
West Nile virus disease cases have been reported from all 48 lower states. The only states that have not reported cases are Alaska and Hawaii. Seasonal outbreaks often occur in local areas that can vary from year to year. The weather, numbers of birds that maintain the virus, numbers of mosquitoes that spread the virus, and human behavior are all factors that can influence when and where outbreaks occur.

Find Kansas specific data on WNV human cases and mosquito surveillance updated weekly at http://www.kdheks.gov/epi/arboviral_disease.htm.
How can people reduce the chance of getting infected?
The most effective way to avoid West Nile virus disease is to prevent mosquito bites.
KDHE recommends the following precautions to protect against West Nile virus:

  • When you are outdoors, use insect repellent containing an EPA-registered active ingredient on skin and clothing, including DEET, picaridin, oil of lemon eucalyptus, or IR3535. Follow the directions on the package.
  • Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
  • Make sure you have good screens on your windows and doors to keep mosquitoes out.
  • Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.

Where can I find more information on West Nile virus?
Visit www.cdc.gov/westnile for more information about West Nile virus.

Weekly Kansas West Nile virus surveillance information can be found on our website here: http://www.kdheks.gov/epi/arboviral_disease.htm.

West Nile virus case counts are updated each Tuesday on our website here: http://www.kdheks.gov/epi/case_reports_by_county.htm

News Releases:
08-19-14 = First Human West Nile Virus Positive Case Reported in Kansas for 2014