Summer brings risk of mosquito-borne illness

July 14, 2018

“West Virginia is a historically low-incident mosquito-borne (illness) busy state,” said Miguella Mark-Carew, director of epidemiology and prevention services for the state Department of Health and Human Resources. “We do have endemic diseases like West Nile virus and La Crosse encephalitis that we get a handful of cases every year.”

Mark-Carew said normally the state does not see an increase in cases until August and September. The mosquito-borne illness season is generally from May to October.

Mark-Carew said there was a concern for West Nile virus in West Virginia, due to a high level nationally.

As of July 10, 30 states reported West Nile virus infections in people, birds or mosquitoes in 2018, according to data from the U.S. Centers for Disease Control and Prevention. Fourteen human cases across the nation have been reported to the CDC this year.

Mark-Carew pointed to 2012 for the concern, a year when 10 cases of West Nile virus in West Virginia were reported to the CDC. There were 5,674 cases reported to the CDC across the nation that year, while in the year prior there were only 712.

Most people infected with West Nile virus, spread mainly through mosquito bites, do not show symptoms, according to the CDC. About one in five people will develop symptoms like a fever and about one in 150 will become seriously or fatally ill.

Last year, there were four reported cases of La Crosse encephalitis and one case of the West Nile virus in the state, Mark-Carew said.

Like the West Nile virus, most who contract the mosquito-borne illness La Crosse encephalitis do not show any symptoms, according to the CDC. Those younger than 16 are most at-risk for severe symptoms. Fever, headache, nausea, vomiting and tiredness are some of the beginning symptoms. Severe symptoms include brain inflammation, seizures, coma and paralysis. Long-term disability or death due to the illness is rare.

La Crosse is the most common mosquito-borne illness in West Virginia, according to the state DHHR. There are 10 to 20 reported cases of La Crosse in West Virginia each year.

Most mosquito-borne illness cases are due to people traveling to other countries, Mark-Carew said. She pointed to two imported malaria cases last year, when the total of the state’s mosquito-borne illnesses were eight. The year before that, there was a single imported malaria case and 11 Zika cases.

There have been three imported malaria cases this year, and there are one to five cases reported in West Virginia annually, Mark-Carew said.

Mosquito-borne illnesses like Chikungunya and Dengue are seldomly diagnosed in West Virginia, according to a Kanawha-Charleston Health Department news release.

In 2017, mosquito surveillance was conducted in 97 places in 23 counties from May 17 to Oct. 26 by the West Virginia Bureau of Public Health’s Mosquito Surveillance Program.

The Kanawha-Charleston Health Department was one of four local health departments actively involved in 2017 mosquito surveillance, according to the West Virginia 2017 Mosquito Surveillance Report.

Mosquitoes were collected using traps and put into test tubes called pools that held between 10 and 50 mosquitoes. They were then sent for testing to a state lab.

The mosquitoes in 2017 were tested for La Crosse encephalitis, West Nile virus, St. Louis encephalitis and the Zika virus, according to the report.

While human cases of West Nile virus are less-reported than diseases like La Crosse, pool tests regularly find West Nile, according to DHHR.

Stanley Mills, director of environmental services for the KCHD, said that last year about 25 percent of the pools were positive for West Nile virus. Only one pool tested positive for La Crosse.

Mills said when pools test positive, it is not possible to know how many of the mosquitoes in it were actually infected.

Some of the ways to reduce the chance of contracting a mosquito-borne illness are the following, according to the 2017 report:

n Wear protective clothing such as long sleeves, pants and socks. Use insect repellent that contains DEET, picaridin, IR3535 or oil of lemon eucalyptus on exposed skin and clothing when outdoors.

n Be aware of the times of day when mosquitoes are most active. For many mosquitoes, peak hours are dusk and dawn. LAC-transmitting mosquitoes are active during the day.

n Ensure that window and door screens are intact to keep mosquitoes outside of homes. Remove breeding sites around the home (e.g. any containers that can accumulate water).

n Check with your health care provider when traveling abroad to learn more about mosquito-borne diseases found in that area of the world.

“Enjoy the outdoors, but also it’s important to be safe,” Mark-Carew said. “You protecting yourself then protects other people from getting the disease as well.”

Regardless of worry over mosquito-borne illness, people should avoid getting bitten anyway, Mills said.

“Mosquito bites are just not good, period. People have allergic reactions to them. Sometimes they get secondary infections from scratching,” Mills said.