The West Nile Virus can cause infection that is spread by the bite of infected mosquitoes. It is named after the West Nile district of Uganda in Africa where the virus was first isolated in 1937. The virus has now been identified here in New Mexico. The virus was first recognized in the US in 1999 as the cause of severe and fatal human illness in metropolitan New York City. The principal transmission cycle of the virus involves several species of mosquitoes and various species of birds. Mosquitoes become infected with the virus when they feed on a bird carrying the virus in its blood. The virus is located in the mosquito's salivary glands. After an inoculation period of 10-14 days, the virus can be injected during blood feeding into another bird, person, or other animal where the virus replicates and may cause illness.

Following transmission by an infected mosquito, West Nile Virus multiplies in the blood system and crosses the blood-brain barrier to reach the brain. The virus interferes with normal central nervous system functioning and causes inflammation of brain tissue. Most people infected with the virus will not develop symptoms. Those who do may become ill 3-15 days after the bite of an infected mosquito. Mild illness includes symptoms such as fever, headache, body aches, and sometimes skin rash and swollen glands. These symptoms may generally last several days. The virus infrequently results in severe illness causing an inflammation of the brain marked by headache, high fever, stiff neck, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. These severe symptoms may last several weeks, although neurological effects may be permanent. A small number of cases have been fatal. The virus can occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, the virus can be transmitted year round. The risk of severe disease is higher for persons over 50 years of age or who are immunocompromised due to diabetes, HIV, cancer, transplant, etc.

It is important to know that in areas where the virus is circulating, very few mosquitoes are carriers. If a mosquito is a carrier, the odds of a bite transmitting the virus to a person are less than 1%. No specific treatment is available for the West Nile Virus. A vaccine is in the works. In the case of severe infection, hospitalization may be required to give intense supportive care. The most prudent action patients can take in areas with virus activity is prevention:

• By staying indoors at dawn, dusk, and in the early evening, patients can reduce their chances of being infected.
• Wearing long-sleeved shirts and long pants whenever outdoors.
• Apply insect repellents to exposed skin when outdoors. The most effective repellents contain DEET (N,N-diethyl-mtoluamide). The more DEET a repellent contains, the longer time it gives protection from mosquito bites. Use care in applying repellents to children—recommendations are DEET concentrations less than 10% be used in children and no more than 35% DEET for adults. Repellents may irritate the eyes and mouth, so avoid these areas as well as applying repellent to the hands of children. Clothing may be sprayed as well since mosquitoes may bite through clothing. Examples of products that contain DEET are OFF®, Repel®, and Cutter®. Soybean Oil (Bite Blocker®), and Citronella (Skin-So-Soft®, Bug Guard®, Buzz Away®) don't work as well as DEET and wear off faster. Vitamin B and ultrasonic devices are not effective in preventing mosquito bites.
• Do not allow water to stagnate in old tires, flowerpots, trash containers, swimming pools, birdbaths, pet bowls, clogged rain gutters, etc. They promote breeding grounds for mosquitoes to lay their eggs.
• If you leave house windows open, make sure they have screens.
• Place mosquito nets over infant carriers when outdoors with infants.

New Mexico residents can help the tracking of the virus by reporting dead or dying birds and horses that are suspected of being infected to the state health department at 1-800-879-3421, 8am to 5pm, Monday-Friday. Contact your health care provider if you have concerns about your health. If you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches, you should see your doctor immediately.

Reference: http://www.health.state.nm.us/ and http://www.cdc.gov/ (Centers for Disease Control and Prevention)

This weeks article submitted by Dale Atencio, Pharm D. candidate, University of New Mexico College of Pharmacy.

[Return to Archive Index]

[PageTop]