West Nile Virus

                                   Important Facts

 

 

 

 

What is West Nile virus (WNv)?

West Nile virus is a mosquito-borne disease that can cause encephalitis, or a brain infection.  Mosquitoes acquire the virus from birds and pass it on to other birds, animals and people.  In 1999, WNv first appeared in New York.  Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals.  It is not spread by person-to-person contact and there is no evidence that people can get the virus by handling infected animals.  West Nile encephalitis is caused by West Nile virus, a flavivirus previously only found in Africa, Eastern Europe, and West Asia.  West Nile virus is closely related to St. Louis encephalitis virus (SLE), which is found in the United States.

 

 

How does WNv spread?

Mosquitoes can become infected with WNv by feeding on birds that have the virus in their bloodstream.  Once a mosquito is infected with the virus it can transmit the virus to humans, birds, horses or other mammals through a bite.  People can only become infected with WNv after being bitten by an infected mosquito.  There is no evidence that people can get WNv from infected animals or people, or that people can transmit the WNv to other animals, birds or people.

 

 

Who is most at risk?

People over 50 years of age have the highest risk of developing a severe illness because as we age, our bodies have a harder time fighting off disease.  People with compromised or undeveloped immune systems are also at increased risk, however, anyone can get the virus.

 

 

What are the symptoms of WNv infection?

Most people bitten by infected mosquitoes do not develop any symptoms.  However when symptoms of infection do occur, they usually appear 5-15 days from the time you were bitten.  Most people who are infected show no or only mild symptoms such as: low grade fever, headache, and occasionally swollen lymph glands.  More severe signs and symptoms can include: high fever, stiff neck, muscle weakness, disorientation, brain inflammation (encephalitis), coma and rarely, death.  There is no specific treatment for WNv; however, in more severe cases, intensive supportive therapy is indicated.

What should I do if I think I have been infected with WNv?

Contact your family physician.

 

Why are birds being tested (especially blue jays and crows) for WNv?

They appear to be highly sensitive to the virus and provide a barometer for us to detect WNv activity in your community.  Knowledge of positive birds in your area allows mosquito control agencies to perform more targeted surveillance and control activities.

 

If I live in an area with positive birds and mosquitoes will I get WNv?

It is highly unlikely.  Even in areas where mosquitoes do carry the virus very few mosquitoes are infected (less than 1%).  If the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill.  The chances that you will become severely ill from one mosquito bite are extremely small.

 

CONTROL AND PREVENTION

 

What can I do to reduce my risk of getting WNv?

  1. Wear long pants and long sleeved shirts when outdoors particularly at dawn and dusk.
  2. Make sure screens on windows and doors are in good condition.
  3. Use mosquito repellent when outdoors.  Be sure to use according to the label – less than 10% DEET for children.
  4. Eliminate standing water, old tires, cans and blocked gutters from your property.
  5. Maintain your swimming pools.  Empty, invert or cover swimming pools when not in use.
  6. Keep birdbaths clean.  Change the water at least once a week.
  7. Report mosquito concerns to your local mosquito control agency.
  8. To control mosquitoes inside a house, use a “flying insect spray”.  Be sure to use according to directions on the label.

 

For more information regarding mosquitoes and measures for prevention and control of mosquito breeding, contact Harris County Mosquito Control at (713) 440-4800 or log on to www.harriscountyhealth.com.   If you live outside of Harris County, please contact your local mosquito control department.  Additional information is also available by logging on to www.cdc.gov.

                       

 

Harris County Mosquito Control, 3330 Old Spanish Trail Bldg. D, Houston Texas 77021-2230, (713) 440-4800

 

Updated 7/30/2002