These insect-borne diseases are on the rise. Greenville County can help you prevent them.

Liv Osby | The Greenville News

West Nile virus, Lyme disease and even plague are among the many diseases spread to people by mosquitoes, ticks and fleas, and nationwide the number of these illnesses tripled between 2004 and 2016.

What’s more, nine new insect-borne infections were identified or introduced in the country during that time, according to the U.S Centers for Disease Control and Prevention.

With summer bringing more time outdoors at backyard picnics, camping in the forest and lounging by the lake, the potential for getting one of these infections increases.

Recent rains also mean more of these insects.

“Zika, West Nile, Lyme, and chikungunya — a growing list of diseases caused by the bite of an infected mosquito, tick, or flea — have confronted the U.S. in recent years, making a lot of people sick,” CDC Director Dr. Robert R. Redfield said in a new report.

“And we don’t know what will threaten Americans next.”

More than 642,000 cases of disease from these insects were reported in the U.S. and its territories from 2004 through 2016, according to the CDC.

Tick-borne diseases accounted for more than 60 percent of them, and are expanding beyond their traditional geographic boundaries.

These diseases are widespread, difficult to control, and their growing numbers pose an increasing risk in the U.S., the CDC reports.

And federal health officials say the nation needs to be better prepared to deal with them.

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Small insects carrying major illnesses

The CDC looked at 16 notifiable vector-borne diseases including West Nile, Zika, chikungunya, dengue fever and Eastern equine encephalitis — which are spread by mosquitoes — as well as Lyme disease, ehrlichiosis, Rocky Mountain spotted fever, anaplasmosis, Southern tick-associated rash illness and tularemia, which are spread by ticks.

Nationwide, the most common tick-borne diseases in 2016 were Lyme disease and ehrlichiosis. West Nile, dengue and Zika were the most common mosquito-borne illnesses.

In South Carolina, Rocky Mountain spotted fever and Lyme disease are the major tick-borne diseases, according to the state Department of Health and Environmental Control

Rocky Mountain spotted fever grew from 45 cases in 2005 to 95 in 2017, while Lyme disease cases grew from 10 to 77 during that time.

There also were a handful of cases of erlichiosis.

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Early spotting can reduce chance of tick diseases

Rocky Mountain spotted fever is the primary tick-borne disease in the Upstate, said Dr. Bill Kelly, infectious disease specialist with Greenville Health System.

“And this actually could be a pretty bad tick year because of all the rain we've had, which means the vegetation the ticks live on and can hide in will be more abundant than in drought years,” he told The Greenville News.

“With ticks, it’s kind of an inevitable thing as we move more into forested areas ... but ticks have to be embedded for a number of hours before they can cause disease. So it’s important that people make sure they find them,” he added.

“But the tick that causes it is bigger, and people usually see it before it gets embedded.”

Most people who get Rocky Mountain spotted fever will have a fever, headache and rash, according to the CDC, but it can be deadly if not treated early.

More heat means more insects

So why are these diseases on the rise?

Climate change is one of the leading causes, said Dr. Leon Bullard, medical consultant with DHEC.

“The main reason we’re making a diagnosis more frequently is that vectors are increasing in numbers based on climate change,” he said.

“That means warmer temperatures that stay warmer for a longer period of time during the year," he added. "And moisture from tropical storms means more breeding grounds for mosquitoes.”

Another reason for the growing numbers, he said, is that physicians are becoming more aware of insect-borne diseases, so reporting has increased.

International travel also plays a role, with insects moving rapidly from one area of the world to another in planes and ships, he said.

Infected people can also bring an illness from another part of the world, he said. So someone with Zika can be bitten by a mosquito which can then transmit that infection to another person.

There have been a handful of cases of Zika, dengue fever and chikungunya in South Carolina, according to DHEC, but they have all been imported by people who traveled to another country.

In 2016, for instance, there were five cases of dengue, including two in Greenville County; 57 cases of Zika, including nine in Greenville County and one each in Pickens and Oconee counties; and three cases of chikungunya, two in Greenville County and one in Anderson County.

West Nile depends on 'right conditions'

West Nile virus is transmitted by mosquitoes in the Palmetto State, though.

“In South Carolina, West Nile virus is the one we should be most concerned about,” Bullard said.

Last year, there were 17 confirmed cases in Anderson, Beaufort, Greenville, Horry, Richland, Union and York counties, including one death in Anderson County, DHEC reports.

There were eight cases in 2016.

But West Nile is sporadic and depends on ecological conditions from year to year, such as the number of birds that have the virus, Kelly said. There were 29 cases in 2012, for instance, the CDC reports.

“It’s prevalent in an area for a year or two and then not so much for a while, then it pops back up,” Kelly said.“You need the right weather conditions and the right mosquito conditions and the right bird conditions at the same time to get a significant outbreak.”

Still, 9 out of 10 cases of West Nile are never reported, Kelly added, because those infected have no symptoms, which can range from fever and body aches to stiff neck, disorientation, coma, convulsions, paralysis and death in severe cases.

Kelly suspects the climate and mosquito ecology here aren't ripe for Zika and dengue to become major endemic diseases, compared with places like South Florida, where winters are warmer and different species of mosquitoes carry the germs.

“This time of year particularly, when you have people with unexplained fevers and things that just don’t look like common infections that we have here, if it looks right for it we’ll test for it,” he said. “But it’s seldom the first thing you think of unless there is a history of travel.”

Better prepared

So what can be done about this growing threat?

The CDC, which provides funding for state detection and response programs, said the nation needs to be better prepared by adding resources at the state and local level for diagnosing and reporting cases, for controlling mosquitoes and ticks, and for developing new diagnostic and control tools.

Bullard said DHEC keeps track of these diseases. If someone returns from another country with Zika, for instance, it will conduct mosquito control in that area so that local mosquitoes can’t contract the disease, he said.

And should there be an uptick in any of these diseases, the agency alerts health care providers to be on the lookout, since many of these illnesses mimic the flu, with aches and pains and fever, he said.

Counties run mosquito control programs, Bullard said. There is no eradication program for ticks because there aren't enough tick-borne illness cases to justify it, he said.

In Greenville County, spraying for mosquitoes is available from June 1 to Sept. 31 for residents in the nonincorporated areas of the county and in the cities of Greenville, Greer, Simpsonville and Travelers Rest. The free service is available by calling the mosquito hotline at 864-467-5988.

Anderson County sprays areas that have been identified by DHEC as harboring infected mosquitoes, said Stephen Combs of the county’s emergency management division. The county doesn’t do nuisance spraying for residents but there are private contractors that do, he said.

Kelly said he supports more public health infrastructure, along with efforts to identify mosquitoes and the diseases they’re carrying to help gauge the risks and react when necessary.

“Our nation’s first lines of defense are state and local health departments and vector control organizations,” the CDC's Redfield said, “and we must continue to enhance our investment in their ability to fight against these diseases.”

How to protect yourself

► Use insect repellent containing DEET, except on babies younger than two months old.

► Wear long-sleeved shirts and long pants when outdoors.

► Treat boots, pants, socks and tents with permethrin.

► Control ticks and fleas on pets.

► Look for ticks on family members and pets daily and remove them.

► Control these insects inside and outside the home by using intact window and door screens, using a mosquito net if there are no screens or if sleeping outdoors, and emptying any container where water can collect — from buckets to flower pots — where mosquitoes can breed.

► Change bird bath water at least weekly.

► Discard old tires where mosquitoes can breed.

Source: CDC

► Greenville County Mosquito Control Hotline: 864-467-5988

To learn more, go to www.cdc.gov/vector