What's Going Around?

West Nile Virus

West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. Despite the fact that west nile virus is a global health threat, there is little understanding of the pathogenesis of this disease. Since there is currently no specific treatment for west nile virus, it is important to understand the biology of this virus to help devise vaccines and new treatments for the West Nile Virus infection. From laboratory testing we do know that an IgM WNV antibody is generally detectable by the time that symptoms appear, while the IgG antibody may not be detectable until 4-5 days following onset of illness.

What's Going Around, West Nile Virus

In general an IgM antibody is considered your first specific immune response against too many organisms. It is generated by the immune system when the body is initially exposed and usually dissipates a few months after an illness. An IgG antibody is the secondary specific immune response against that organism and will remain in the body long period of time.

Diagnosing WNV infection is sort of a tricky process. The laboratory will first look for the specific IgM antibody to WNV that is produced by the immune system in a current infection. The lab will also look for the IgG antibody to WNV that would indicate past infection. The first tricky part is the IgM antibody to WNV has been known to linger in patients for up to a year or more after the first exposure. However testing for the IgM antibody is still the most reliable means to indicate a current infection. The second tricky part to consider is that the antibodies induced by WNV are also cross-reactive with other flaviviruses (a similar family of viruses like St. Louis Encephalitis and Dengue) further complicating diagnosis. A positive diagnosis for a current infection comes only if the patient has physical symptoms combined with a positive IgM antibody that has been confirmed by yet another assay, such as the plaque reduction neutralization assay performed at the Center for Disease Control to rule out those other cross-reactive viruses.

What Are the Symptoms of WNV?

  • No Symptoms in Most People. Approximately 80 percent of people who are infected with WNV will not show any symptoms at all.

  • Mild Symptoms in Some People. Up to 20 percent of the people who become infected will display mild symptoms, including fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms typically last a few days.

  • Serious Symptoms in a Few People. Less than 5%, about 10 in 200 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. Less than 10% of the seriously ill patients will die.

What Causes all the Damage?

Possibly adding to the damage caused by the virus is a protective coating called a viral capsid. It is a destructive protein that can trigger what''s called apoptosis (the automatic self-destructive program within each cell) inside infected cells.

How Soon Do Infected People Get Sick?

Typically symptoms develop in people between 3 and 14 days after they are bitten by the infected mosquito.

How is WNV Infection Treated?

There is no specific treatment for WNV infection. In cases with mild symptoms, people experience symptoms such as fever and aches that pass on their own. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing and nursing care.

What Should I Do if I Think I Have WNV?

For most people you might not know you have even had it. A mild case of WNV illness improves on its own, and people do not generally need to seek medical attention for this infection. If your symptoms of WNV develope into a severe illness, unusually severe headaches or confusion, seek medical attention immediately. Severe WNV illness usually requires hospitalization. Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that could be WNV.

How Can I Prevent WNV?

When dealing with West Nile virus, prevention is your best approach. Fighting mosquito bites reduces your risk of getting this disease, along with other diseases that mosquitoes can carry. Take the commonsense steps below to reduce your risk, such as:

  • Avoid places where mosquito bites are more prevalent, open fields near ponds etc...

  • Clean out standing water where you live, work or play. Standing water provides a place for egg laying.

  • Help your community control the disease by reporting dead birds. Birds can carry the disease then transmit the virus when the mosquito grabs a blood meal from the infected bird. Dead birds that test positive can alert local authorities that the bird population in that area might be infected and allowing insecticides to be sprayed to control the mosquito population that might feed on those birds.

  • Get double protection: wear long sleeves during peak mosquito biting hours, and spray DEET repellent directly onto your clothes.

The #1 Thing to Remember about WNV

The chance that any one person is going to become ill from a mosquito bite remains low. Most people who are infected with the virus will not develop any symptoms at all. The risk of severe illness and death is highest for people over 50 years old and the immuno-compromised.

What's Going Around?