Summer brings West Nile Virus threat

06/05/2017 12:00 PM
TAHLEQUAH, Okla. – As spring turns to summer, more people will venture outdoors for activities, which means increased exposure to mosquitos and possibly the West Nile Virus some mosquitos carry.

Experts at the Centers for Disease Control believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall.

According to the CDC, the virus can be a life-altering and sometimes fatal disease. In 2012, the CDC reported 5,674 confirmed human cases of WNV with 286 of them resulting in death. The CDC states that every state in the U.S., except Hawaii and Alaska, reported WNV cases in 2012. In Oklahoma, 178 humans were diagnosed with WNV with 15 deaths in 2012, according to the Oklahoma State Department of Health.

The CDC states that about one in 150 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.

Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. Approximately 80 percent of people who are infected with WNV will not show any symptoms at all, according to the CDC.

The CDC has predicted it could be a bad year because of weather conditions that promoted breeding of the mosquitoes that spread the virus to people.

In Oklahoma, the WNV season runs from May to November. People are at greatest risk of exposure to infected mosquitoes from July through October in the state. People of any age can become ill after being bitten by an infected mosquito, but those over the age of 50 are at greater risk of developing serious illness involving the nervous system.

The OSDH advises use of insect repellents – particularly those containing DEET, picaridin, oil of lemon eucalyptus (PMD), or IR 3535 – when outdoors. The types of mosquitoes that transmit WNV are most active during early morning and evening hours, so take mosquito bite precautions during those times. It is also recommended to drain or treat standing water around your home with a mosquito larvacide to reduce mosquito-breeding sites.

How does WNV spread?

Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals.

In a small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.

How soon do infected people get sick?

People typically develop symptoms between three and 14 days after they are bitten by an infected mosquito.

How is WNV infection treated?

There is no specific treatment for WNV infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own, although even healthy people have become sick for several weeks. 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?

Milder WNV illness improves on its own and people do not necessarily need to seek medical attention for this infection though they may choose to do so. If you develop symptoms of severe WNV illness such as 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.

What is the risk of getting sick from WNV?

People over 50 at higher risk to get severe illness. People over the age of 50 are more likely to develop serious symptoms of WNV if they do get sick and should take special care to avoid mosquito bites.

Is there a vaccine against West Nile encephalitis?

No, but some groups are working towards developing a vaccine.

What can be done to prevent outbreaks of WNV?

Prevention and control of WNV and other arboviral diseases is most effectively accomplished through integrated vector management programs. These programs should include surveillance for WNV activity in mosquito vectors, birds, horses, other animals and humans and implementation of appropriate mosquito control measures to reduce mosquito populations when necessary. Additionally, when virus activity is detected in an area, residents should be alerted and advised to increase measures to reduce contact with mosquitoes.

How often should repellent be reapplied?

In general you should re-apply repellent if you are being bitten by mosquitoes. Always follow the directions on the product you are using. Sweating, perspiration or getting wet may mean that you need to re-apply repellent more frequently. Repellents containing a higher concentration (higher percentage) of active ingredient typically provide longer-lasting protection.

Which mosquito repellents work best?

CDC recommends using products that have been shown to work in scientific trials and that contain active ingredients that have been registered with the Environmental Protection Agency for use as insect repellents on skin or clothing. When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that EPA does not expect a product, when used according to the instructions on the label, to cause unreasonable adverse effects to human health or the environment.

Of the active ingredients registered with the EPA, CDC believes that two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature. Products containing these active ingredients typically provide longer-lasting protection than others:


• Picaridin

Oil of lemon eucalyptus, a plant-based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the U.S. it provided protection similar to repellents with low concentrations of DEET.

Can insect repellents be used on children?

Repellent products must state any age restriction. If there is none, EPA has not required a restriction on the use of the product.

According to the label, oil of lemon eucalyptus products should NOT be used on children under 3 years. In addition to EPA’s decisions about use of products on children, look to the opinion of the American Academy of Pediatrics. The AAP does have an opinion on the use of DEET in children. AAP has not issued recommendations or opinions on the use of picaridin or oil of lemon eucalyptus for children.

What guidelines are available for using a repellent on children?

• When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid children’s eyes and mouth and use it sparingly around their ears.

• Do not apply repellent to children’s hands.

• Do not allow young children to apply insect repellent to themselves; have an adult do it for them.
• Keep repellents out of reach of children.

• Do not apply repellent under clothing. If repellent is applied to clothing, wash treated clothing before wearing again.

How else can I protect children from mosquito bites?

Using repellents on the skin is not the only way to avoid mosquito bites. Children (and adults) can wear clothing with long pants and long sleeves while outdoors. DEET or other repellents such as permethrin can also be applied to clothing, as mosquitoes may bite through thin fabric. Also, mosquito netting can be used over infant carriers.

Prevention Tips

Be aware of peak mosquito hours

The hours from dusk to dawn are peak biting times for many species of mosquitoes. Take extra care to use repellent and protective clothing during evening and early morning or consider avoiding outdoor activities during these times.

Install or repair screens

Some mosquitoes like to come indoors. Keep them outside by having well-fitting screens on both windows and doors. Offer to help neighbors whose screens might be in bad shape.

Dispose of breeding grounds

Also, it may be possible to reduce the number of mosquitoes in the area by getting rid of containers with standing water that provide breeding places for mosquitoes.

Help reduce the number of mosquitoes in areas outdoors where you work or play, by draining sources of standing water. In this way, you reduce the number of places mosquitoes can lay their eggs and breed.

At least once or twice a week, empty water from flowerpots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.

Check for clogged rain gutters and clean them out.

Remove discarded tires, and other items that could collect water.

Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.


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