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West Nile Virus: By Beverly Clensey, CNP
July 7, 2015

Summer has just started.  People are enjoying the warm weather and outdoor activities like gardening, picnics, outdoor sports as a player or spectator, or just relaxing in the back yard.  What comes with the warmer weather from June to September are mosquitoes.  These pesky little insects can carry the West Nile Virus and make you sick.

The West Nile Virus (WNV) is the most common arbovirus.  An arbovirus is a group of viruses that is transmitted to other animals by an arthropod which includes insects, spiders, ticks, and mosquitos.  The WNV arthropod is the mosquito, but the animal that the mosquito gets the virus from is a bird. This mode of transmission is called the bird-mosquito-human cycle. The mode of transmission to humans is from the bite of an infected mosquito.

The first thing that happens in this cycle is a bird becomes infected with the virus.  More than 100 different birds have been reportedly infected with the virus.  The most common infected birds are crows, ravens, and blue jays. Some of the birds may die while others will show no symptoms of the virus.  The handling or eating the meat of an infected dead bird is a possible risk factor for WNV exposure.

The next step in the cycle is that the mosquito feeds on or bites the infected bird.  The mosquito then becomes a carrier of the WNV.  As a carrier, the mosquito can transmit the virus to an uninfected bird or another mammal like humans or horses. An infected female mosquito can transfer the virus to their eggs.  Therefore, the offsprings (baby mosquitoes) would be infected and become carriers of the virus.  In this step of the cycle, the WNV can be kept alive by increasing the number of birds that have the virus and the number of mosquitos that carry the virus.

The last step in the cycle is the mosquito bites a human.  The virus is transferred through the salvia of the mosquito and is absorbed into the human blood stream.  After a person is bitten or exposed to the mosquito salvia, symptoms range from no symptoms of the WNV to severe, life-threatening symptoms.  There is no human to human transmission of the WNV. Therefore, a person with WNV is not contagious.

Symptoms occur 2 to 14 days after being bitten. Most people will show symptoms within 2 to 6 days.  Approximately 80% of patients infected with WNV have no symptoms or present with non-specific symptoms. The nonspecific symptoms are fever, headache, fatigue, muscle aches, back pain, nausea, vomiting, diarrhea, and decreased appetite. A distinguishing symptom from other viral illness for WNV is a transient flat and bumpy, red rash. The non-specific symptoms may last a few days to several weeks.   The plan of care is symptom and supportive care with over the counter pain and fever lowering agents like ibuprofen, acetaminophen or naproxen.

In severe WNV, less than 1% will present seriously ill with severe neurological symptoms of encephalitis and/or meningitis. This occurs when the virus has spread to the brain and spinal cord. Encephalitis is when the brain becomes infected with the virus.  Meningitis is when the lining of the spinal cord and brain become infected with the virus.  Symptoms of encephalitis and meningitis are high fever, headache, seizures, and possible coma and muscle paralysis. These symptoms may last several weeks.  Full recovery from severe WNV occurs in 40% of the population. Some people will have long term disability while approximately 10% of the severe illnesses will end in death.  The people that are at greater risk for the development of WNV are those greater than 50 years of age, especially the elderly, those with chronic medical conditions, and those with recent mosquito bites.  The plan of care usually requires hospitalization for supportive care.

Prevention is the best plan of care. Limit exposure by staying in the house when mosquitos are most active. Mosquitos are most active in early morning and late evening.  Replace or repair damaged screens and windows to prevent mosquitos from getting in the house.

Apply insect repellent to your skin. The best insect repellents contain 10% to 35% DEET or diethyltoluamide.  The higher the percentage of DEET the longer the repellent is effective. The insect repellents work by affecting the smelling receptors of the mosquito that would have attracted the human scent or changes the human scent to a bad smell to the mosquito.

Wear protective clothing, long sleeve shirts and pants, to prevent direct mosquito contact with the skin. Spray your clothing, not your skin, with Permethrin containing products like Sawyer Permethrin Clothing Insect Spray or Repel Permethrin Clothing and Gear which adds an additional protection. A better result occurs if the clothing is sprayed on the inside and outside approximately one hour before outside activities. 

Remove any standing water near the perimeter of the house to control the mosquito population. Female mosquitoes lay their eggs in stagnant water.  Change water in bird baths and animal water bowls frequently. Clean gutters of debris, empty rain barrels, buckets, and tire swings to prevent stagnation of water. Use gloves when handling dead birds or animals. 

Electronic devices that emit high pitched sounds unheard by the human ear have not shown to notably control the mosquito population.  Other agents like Citronella, botanical oils like sandalwood, geranium, and soybean or eating strong smelling foods like garlic, onions, cruciferous vegetables or mineral sulfur have not shown helpful against mosquito bites.

Beverly Clensey is a certified nurse practitioner at Madison Health Primary Care in West Jefferson and is currently accepting new patients.  To make an appointment, call 614-879-8141.


Madden, Ken. (2003). West Nile virus infection and its neurological manifestations. Clinical Medical Research. April 1(2): pp.145-150 retrieved from http:// www.ncbi.nlm.nih.gov.




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