A recent Texas study found that the West Nile virus is deadlier than researchers and doctors once thought.

The Centers for Disease Control and Prevention has stated the West Nile virus has a fatality rate of roughly 4 percent, but a recent study from the Baylor College of Medicine in Houston suggests the fatality rate could be as high as 13 percent.

The study analyzed data from all 4,162 cases of West Nile reported to the Texas Department of State Health Services between July 2002 and December 2012. Out of those cases, 289 people died of the disease within the first 90 days of infection. A remaining 268 people died after the initial onset of the illness, and it’s this number that has researchers and doctors taking notice.

The patients who died after 90 days had already recovered from the illness but were left vulnerable to other infectious diseases, according to the study. Those patients had a higher risk of dying from kidney problems and renal failure than the general population.

West Nile is a mosquito-borne virus that first came to America in 1999. It causes symptoms in about one out of every five people infected.

In Collin County this year, 21 people have tested positive for West Nile, according to the state health department. People who contract the West Nile virus fall into two categories. The first are people who develop West Nile Fever — 10 people have contracted this in Collin County. Second are the people who develop neuroinvasive disease, a condition where the virus travels to the brain or spinal cord, according to the CDC. Eleven people have developed this in Collin County in 2016.

One person in Grayson County died of the neurovinvasive disease in October.

“Just having experienced the first death in the county from the West Nile virus, we take it very seriously,” Josh Stevenson, the emergency preparedness manager for the Grayson County Health Department, said. “And this particular time of year is really the most dangerous time of year for West Nile Virus.”

Temperatures have stayed mild this year and it will take at least two hard freezes before mosquitoes will be killed off for the winter, Stevenson said.

In the meantime, evening events such as parades and farmers markets are getting more people outdoors, meaning more people can be bitten.

Stevenson said people should take precautions by applying a bug spray with deet whenever they’ll be outside around dawn or dusk, the time of the day the mosquitoes carrying West Nile are most active.

He said that 20 years ago the worst thing a person could get from a mosquito was a bump on the arm. Now, he said, there’s West Nile and the Zika virus to contend with and he urges people to take precautions and protect themselves.

“It’s not a nuisance anymore,” he said. “Now it’s a public health risk and just like we have to put on sunscreen when we go outside, now when you go outside during mosquito season you need to put on some deet and take precautions.”

Anna City Manager Philip Sanders said the city has not sprayed for mosquitoes this year and has no plans to.

“I encourage people to practice self-protection,” he said

In addition to using deet, the CDC recommends people remove all standing water from their yards, and limit their time outside during peak mosquito times.

Sanders said the city works with the Collin County Health Department to trap and test mosquitoes. Only if several tests came back positive for the virus in a populated area would the city would consider spraying.