West Nile Virus Begins to Percolate in Texas
By Jessica Ridge

Arboviral, or arthropod-borne, disease season in Texas is underway, with 17 cases of West Nile virus and 26 cases of dengue in humans confirmed in the state by mid-August, warranting vigilance and patient education.  

Arboviral illnesses are a subset of vector-borne illnesses, a broader category of diseases that can be transmitted to humans by mosquitoes, fleas, lice, and ticks, among other vectors.  

Susan McLellan, MD, an infectious diseases physician at UTMB John Sealy School of Medicine in Galveston, describes West Nile and dengue as the two arboviruses most commonly diagnosed in Texas. With no way to determine from looking at a patient with a fever whether they might have West Nile, dengue, or another arbovirus that may be imported, thinking about those diseases as a possibility and asking about travel and other exposures is important, she says. 

“West Nile virus we have every year,” said Dr. McLellan, who sits on the Texas Medical Association’s Committee on Infectious Diseases. “Dengue is pretty rare to be acquired in the continental U.S. at the current time, although with climate change that could change, and there continues to be a concern that dengue could spread further within the continental U.S., with local spread.” 

She notes that it’s typical to begin seeing cases of West Nile virus in summer and points out that the current number of cases in Texas is not an increase over recent years, which a graph from the Texas Department of State Health Services’ (DSHS) arboviral activity report illustrates. 

Current year data for West Nile virus case counts by state and county are maintained by the Centers for Disease Control and Prevention. 

The virus is “the [arboviral disease] most likely to worry about acquiring here in the boundaries of Texas,” Dr. McLellan said. “Many people will only have a fever, and often in that case it may not be recognized as West Nile virus unless they get a specific test.”  

West Nile can cause severe brain infection, meningitis, or severe encephalitis, she says, with older patients more likely to be affected. 

With no obvious identifier for arboviral diseases, physicians should be mindful of their possibility, Dr. McLellan says. Cases are typically first visible in counties and areas where there are strong programs for surveillance, she notes, often via mosquito trapping or the use of sentinel birds.  

As some of those proactive efforts may be dropped or scaled back amid a pullback in federal funding of public health efforts, “we miss chances to know ahead of time and to be aware,” Dr. McLellan said. 

Additional arboviruses endemic to Texas include St. Louis encephalitis and Eastern equine encephalitis, Dr. McLellan says. Chikungunya and Oropouche arboviral diseases have been more associated with travel.  

DSHS describes dengue as endemic in most tropical countries of the South Pacific, Asia, the Caribbean, the Americas, and Africa, with sporadic outbreaks having occurred along the Gulf Coast and in far South Texas.  Dr. McLellan emphasized the importance of checking travel history as part of a physician’s evaluation of a sick patient. 

Dr. McLellan recommends physicians counsel patients on simple infection prevention methods, namely preventing mosquito bites. DSHS provides actionable tips for preventing mosquito bites and mosquito breeding. 

Physicians can also tell patients to call their county health department to let them know if mosquitoes are becoming a nuisance, and to ask if they will spray or increase other control measures. Combined with proactive surveillance, those communitywide measures are part of a larger public health infrastructure. 

“It’s incredibly important that we maintain funding and understand the importance of the activities that are done by our public health partners,” Dr. McLellan cautions. “The main thing is to take it seriously.”