West Nile Virus

Cases of West Nile Virus infection are on the rise in the U.S.  Already over 1,100 cases and 41 deaths have been reported in 47 states.  Though most cases of the infection are relatively mild, more severe infections can be life-threatening, particularly in the elderly.  

West Nile Encephalitis, a viral infection that can cause swelling of the brain, was first seen in the U.S. in 1999.  The disease is native to Africa, Asia, Europe and Australia. 

Humans, birds and horses have died from the infection.  It is therefore presumed that the disease came to America in 1999 through the importation of an infected mosquito or bird from the Middle East.  

Infected birds carry the virus in their bloodstream.  Mosquitoes that bite these infected birds can then pick up the virus and transmit it to humans by biting them.  Many varieties of birds can harbor the virus, including crows, robins, sparrows, gulls, blue jays, hawks and falcons.  Since 1999, there have been about 30,000 confirmed West Nile infections and over 1,200 deaths from the disease in the U.S.  

Most infections occur in summer or early fall.  Risk factors for West Nile infection are outdoor activity, lack of application of insect repellents and standing water around residential areas that serve as a breeding ground for mosquitoes.  The peak time of day for mosquito bites is from dusk to dawn.  

Since the cause is viral, many of the typical symptoms can be very general: fever, headache, body aches, neck pain, nausea and vomiting.  About one in 150 infected persons will develop more severe illness with inflammation of the brain (encephalitis) and central nervous system.  These people can develop behavioral changes such as irritability, confusion and disorientation, as well as muscle weakness or rigidity, or tremors.  Persons older than 50 years old are at higher risk for developing severe illness.

To determine if someone has the disease, all of the signs and symptoms should be examined together.  If the sick individual has the typical symptoms, it is mosquito season, the individual is 50-plus-years-old, and there has been confirmed infection in regional birds or unexplained bird deaths, then West Nile infection would be suspected.  A blood test may then be performed to detect the virus.

Like most viral infections, there is no specific treatment for West Nile Encephalitis.  Medicines to treat high fever and discomfort can offer relief of symptoms.  Severely ill individuals may need hospitalization and observation.  

The key is prevention.  Insect repellents containing DEET, picaridin, IR3535 and the plant-based oil of lemon eucalyptus are all recommended by CDC.  Repellents containing DEET or picaridin provide the longest and most effective protection against mosquito bites.  

Use screens in windows and doors to keep mosquitoes outdoors.  Get rid of standing water around your home.  If standing water cannot be removed, use a mosquito larvacide (available at hardware stores).  Finally, see your doctor if you develop unusual symptoms.  No vaccine has yet been developed to prevent the disease in humans.  

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices Family Medicine in Chesterfield.

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