First Texas Case of West Nile Virus and a Global Increase in Dengue Virus Cases Highlights Need for Mosquito Precautions

Public health officials urge Texans to be vigilant in protecting against mosquito bites after confirming the first Texas case of West Nile virus and 10 travel-associated dengue cases for 2024. Precautions should be taken in Texas and while traveling internationally to countries where dengue is endemic.

The first case of West Nile in 2024 was reported in a Montgomery County resident who has been diagnosed with West Nile fever. As of today, the Texas Department of State Health Services has identified nearly 800 mosquito samples infected with West Nile virus in 24 counties.

West Nile virus is transmitted through the bite of infected mosquitoes. Most people exposed to the virus don’t get sick, but about 20 percent develop symptoms like headache, fever, muscle and joint aches, nausea and fatigue. In a very small proportion, less than one percent, the virus affects the nervous system, leading to the more serious West Nile neuroinvasive disease that can cause neck stiffness, disorientation, tremors, convulsions, paralysis and even death.

All of the dengue cases reported in Texas so far in 2024 were acquired while traveling internationally, but a small number of dengue cases have been acquired from mosquito bites in southern Texas in recent years. The Centers for Disease Control and Prevention recently alerted health care providers about the increased risk of dengue virus infections in the United States in 2024 based on an unprecedented number of cases being reported globally and higher-than-expected cases identified among U.S. travelers. Most dengue virus cases in the US have been linked to travel to places where the virus is endemic, including most tropical countries of the South Pacific, Asia, the Caribbean, South and Central America and Africa.

Dengue virus is transmitted by infected mosquitoes and about 25 percent of infections become symptomatic. After about three to 14 days, infected people may develop a fever, nausea, vomiting, rash, muscle aches, joint pain, bone pain, pain behind the eyes and headaches. Most people recover completely within two weeks. However, about one in 20 symptomatic people develop a severe infection called Dengue Hemorrhagic Fever that can be fatal if untreated.

“Unfortunately, many mosquitoes in Texas are capable of spreading diseases, such as West Nile and dengue. These diseases are often mild, but some people will develop severe illness,” said DSHS Commissioner Jennifer Shuford, MD, MPH. “So, it is important for Texans to know how to protect themselves against mosquito bites.”

Heavy, widespread rain from Hurricane Beryl has left behind standing water that provides mosquitoes ample breeding ground to multiply. An increase in nuisance mosquitoes may initially occur in areas impacted by the storm. This may be followed by an increase in the types of mosquitoes that can spread diseases like West Nile. People working on clean up and recovery should take steps to protect themselves from mosquito bites.

The Texas Department of State Health Services urges people to not give mosquitoes a biting chance by following these steps to protect themselves and their families from West Nile and other diseases spread by mosquitoes.

• WEAR long sleeves and pants. Create a barrier to mosquito bites by covering up.
• APPLY insect repellent. Use EPA-registered repellent such as those containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol or 2-undecanone.
• REMOVE standing water. Emptying out water that accumulates in toys, tires, trash cans, buckets, clogged rain gutters and plant pots will deny mosquitoes a place to lay their eggs and reproduce.

People should also keep mosquitoes out of their homes by using air conditioning and making sure window and door screens are in good repair. DSHS urges people with West Nile or dengue symptoms to contact their health care provider and mention any exposure to mosquitoes.

There were 154 cases of West Nile disease in Texas last year and 13 deaths.* Over the last five years, Texas has had 497 cases and 68 deaths. There were 79 cases of dengue in Texas last year, including one locally acquired case in Val Verde County. Mosquitoes remain active in much of Texas into November and December.

* Cases and attributed deaths for 2023 are provisional.

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(News Media Contact: pressofficer@dshs.texas.gov)