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The following frequently asked questions about the West Nile Virus (WNv) are based on information posted on the Harris County Public Health & Environmental Services (HCPHES)'s web site. Also included are school guidelines for student use of insect repellent.

What is the West Nile Virus?

The virus is a mosquito-borne disease that may cause a range of symptoms or no symptoms at all, and, in very rare cases, death. The information that we have been given indicates that HCPHES Mosquito Control Division is spraying for mosquitoes in this area on a regular basis.

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, or animals through a bite. People can only become infected with WNv after being bitten by an infected mosquito. There is no evidence that people, birds, or domestic animals can transmit the WNv to others.

Who is most at risk?

People over 50 years of age have the highest risk of developing a severe illness if infected with WNv. People with compromised or underdeveloped immune systems are also at increased risk. However, anyone can contract the virus.

What are the symptoms of WNv infection?

If bitten by infected mosquitoes, most people do not develop any symptoms of infection. However if symptoms do occur, they usually appear 5-15 days after the time of the bite. Mild symptoms may include low grade fever, headache, and/or swollen lymph glands. In rare cases symptoms include high fever, stiff neck, muscle weakness, disorientation, brain inflammation (encephalitis), coma, and death. While there is no specific treatment for WNv, intensive supportive therapy is indicated for severe cases.

How can risk be reduced?

Eliminate any standing water around the house. Keep birdbaths clean, and change the water at least once a week.

Mosquitoes are most active between dusk and dawn. If outside activities cannot be avoided during late evening or very early morning hours, the following tips may be helpful:

• Apply insect repellent sparingly to exposed skin. Always read the instructions before using any insect repellent. The most effective repellents contain a chemical called DEET. The CDC recommends repellent with 30-35% DEET for adult use. Small children and infants should not use full-strength insect repellent containing DEET. Use repellent with less than 10% DEET for small children and/or consult your physician.

When applying repellent:

• Use sparingly. Do not cover skin/clothes heavily.
• Do not spray repellent directly onto your face. Put some on your hands then apply thin layer to face.
• Avoid the mouth and eyes. Repellent can irritate these areas.
• Keep repellent from contacting wounds, cuts, or irritated skin.
• Some insect repellent containing DEET will work for up to 10 hours
• Read the label and apply carefully.

What can parents do?

Parents may want to apply repellent in the morning before school as an extra precaution if students are waiting at a bus stop.

Even though the Health Department advises that no extra precautions need to be exercised during school hours, parents may send repellent to school under the following guidelines:

• Parents must provide written permission to school staff.
• No aerosols will be allowed in school. Parents may send insect repellent lotions, wipes, or pump sprays. Please select an application that your child can easily apply himself/herself. The repellents will be given to the teacher, stored in a secure location, and monitored so that only the student who brings the repellent may use it.
• The guidelines also apply to athletes and other students during extracurricular activities who are outside for extended periods of time in the afternoon and evenings.

It is important to report mosquito concerns to the Harris County Public Health & Environmental Services Mosquito Control Division at 713-440-4800.