West Nile Virus: Symptoms, prevention of mosquito-borne fever that flies under Tennessee's radar

Correction: A previous version of this story misspelled Jason Rasgon's last name. 

Before 1999, West Nile Virus was unheard of in the United States. Then, a case appeared in New York.

Then, a few more cases, in a few other states.

Since sometime in the early 2000s, thousands of cases of the mosquito-borne virus have been reported across 49 states — everywhere except Alaska, so far. 

Tennessee is no exception. West Nile is here to stay. 

The Volunteer State has seen 151 human cases since 2010, according to data from the Tennessee Department of Health. That number includes the nine seen so far in 2018, although those numbers are not yet final.

It's not going away

"Tennessee, as far as states go, has not had that many cases," Jason Rasgon professor of disease epidemiology at Pennsylvania State University said.

Rasgon has been studying West Nile for the past 15 years, and has kept an eye on the way it has spread across the country, to almost everywhere, including Hawaii and Puerto Rico. 

(Hawaii has only had one case, Rasgon said, in 2014, but it has been there.)

"No one talks about it. It hasn't been on the news like I'd want it to be," Tracy Boutsisomphone said. "I'd like some more information on what to do to protect my family."

Boutsisomphone, a mother of five who said her main concern is making sure her family stays safe, just started her first year working for a seasonal pumpkin patch in Nashville's 12 South neighborhood. 

The East Nashville-native makes sure to use bug spray while she works outside.

"I hadn't heard about any of the recent cases," she said. "It's the one (disease)  I worry about, and I just want a heads up."

Some areas more affected than others

Over the past 17 or 18 years, Tennessee has seen a couple of hundred cases, Rasgon said. Compared to states like California, which has seen more like 6,000 in that same period, Tennessee has gotten off somewhat lightly. 

Shelby County has seen the most cases over the years — 62 since 2010. In 2018, Shelby County has reported four deaths so far to the TDOH.

More:4 things to know about mosquito season

The next-most affected is Davidson County, which has seen 18 cases since 2010, including two so far in 2018. In total, 57 Tennessee counties have seen no cases since 2010, but the ones that have are spread all over the state.

One neighborhood in Nashville, near the intersection of Twelfth Avenue South and Acklen Avenue, has seen mosquito populations that tested positive for the virus three times so far this year.

Caroline Cathey, a junior at Belmont University, said she had received a note from the university's health department about the issue, but didn't worry about it as much as she "probably should."

"Not here," fellow Belmont junior Annicka Victorson, said. "I went to Africa in May and I was worried about it when I went there, and I got a shot, but not here."

How sick can it make me?

The majority of people infected, about 80 percent, will never know they have contracted West Nile. 

Others, just about 20 percent per TDOH, will experience flu-like symptoms for a few days — think fever, headache, weakness, stiff neck, nausea, vomiting, muscle aches and pains, rash and in some cases diarrhea and sore throat.

It is only about 1 percent of those infected who really see some serious health problems from West Nile. 

People over the age of 50 are at the highest risk of developing the most severe reaction to the virus, as are immunocompromised patients, including those with HIV or undergoing chemotherapy, Rasgon said. 

For that population of infected persons, the symptoms include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis, according to the Centers for Disease Control and Prevention.

At its most serious, it can cause encephalitis, Dr. William Schaffner, an infectious diseases specialist at Vanderbilt University Medical Center, said. Encephalitis is an infection of the brain that creates serious symptoms; West Nile can cause similar inflammation to the spinal cord.

By its nature, those conditions can exacerbate existing conditions, and more seriously threaten those with cancer, diabetes, hypertension, kidney disease and people who have received organ transplants.

The bad news is that recovery from the most severe reaction to West Nile can take weeks or months, and in some cases can leave permanent damage to the central nervous system. 

The CDC reports that about 10 percent of those who experience severe West Nile-related illness will die from it. 

More:67-year-old Shelby County man dies from West Nile virus

Is there any treatment?

"We don't have a medicine against West Nile," Schaffner said, "but we can take good care of you while your body gets rid of the virus."

Most treatment options for the less severe symptoms are the same as for most viral infections: over the counter pain relievers to reduce fever, the CDC recommends. 

In severe cases, anyone experiencing the high fever and related symptoms should seek medical attention quickly. 

Hospitals can offer supportive care, Schaffner explained, to run encephalitis diagnostic tests, and make sure a patient's heart, kidneys and other organs are running as smoothly as possible to help fight the virus. 

What is West Nile?

West Nile is a virus that, like its fellow infections, affects a host in a way that allows it to replicate itself and then be passed on to other hosts, Schaffner. 

In particular, West Nile likes to infect birds. 

"The West Nile Virus is not after us," Schaffner said. "It would like to get into another bird and perpetuate."

The problem, however, is that mosquitoes don't only target birds.

"Sometimes they'll go off target and bite us," Schaffner said, "and then we become ill."

How do humans get it?

Rasgon explained that some small animals can also be infected from being bitten by an infected mosquito. 

"We're kind of incidental, from the virus' point of view," he said. 

Humans, as well as horses, become "dead end" hosts, Rasgon explained. Even if a person is infected, the virus will not circulate at a high enough concentration in the blood stream to infect another mosquito. Without mosquito intervention, it won't be passed to another creature. 

In some rare cases, West Nile was transmitted through blood transfusion or organ transplant, according to Tiffany Taylor, spokesperson for Tennessee's American Red Cross branch. 

American Red Cross screens all donated blood for several diseases, including West Nile. 

"The Red Cross tests every unit of donated blood from all regions during the entire year for evidence of the virus using West Nile Virus Nucleic Acid Testing," Taylor said in an email. "In areas seeing West Nile Virus activity, we use even more sensitive NAT methods for detection of the virus."

What can you do to prevent it?

"West Nile, even at the height of its transmission, was never what I would consider a serious public health problem," Rasgon said. "It's more of a public relations problem. There just aren't enough people getting sick to warrant the resources and testing (for vaccine makers) to make a vaccine for it."

Most of the advice (from the CDC, from Rasgon, from Schaffner), is just to use common sense when attempting to avoid being bitten by mosquitoes. 

"No one wants to get bit, whether from an infected mosquito or not," Rasgon said. 

Insect repellent, long sleeves and pants, screens and air conditioning are all good options to help keep the pests at bay. 

Mosquito season can last well into October, Brian Todd with the Metro Public Health Department said, until the first killing frost. 

What can be done about the threat?

Nashville's Metro Public Health Department, under CDC guidelines that many municipal health departments also follow, runs a multi-pronged mosquito monitoring program from early March through late October. 

Crews will set up traps to collect batches of mosquitoes, which are sent to the state health department for testing. 

When they test positive for West Nile, the department will alert the neighborhood where the batch was collected of the threat, Todd said. 

"In Nashville, it's rare to have a human case," he said. "We're finding mosquitoes that have it, but that doesn't mean we're also having human cases."

The department also runs "backyard inspection" days to help residents find possible mosquito larvae breeding grounds. 

Areas of standing water that has stagnated, no matter how big or small, can breed mosquitoes. Once they hatch, they'll stay close to a food source — like a back patio where a family hangs out. 

Gutters, if water sits in the bottom of them, can also be a problem. 

Metro will also send crews out to known problem areas, usually low-lying where water will collect and stay, to apply a granular larvicide that will kill the mosquito crop but not harm pets, Todd said. 

Reach Mariah Timms at mtimms@tennessean.com or 615-259-8344 and on Twitter @MariahTimms.