Why is 'St. Louis' included in the name of a rare mosquito-borne virus?

Aug 28, 2025 - 02:00
Why is 'St. Louis' included in the name of a rare mosquito-borne virus?

ST. LOUIS - St. Louis was once the site of an epidemic that inspired the name of a rare mosquito-borne virus across the Midwest.

According to the Centers for Disease Control and Prevention (CDC), St. Louis Encephalitis is a virus spread to people through the bite of an infected mosquito and can cause inflammation of the brain. Although many people infected with the disease do not have symptoms, those who become ill may experience fever, headaches, nausea, vomiting, and tiredness. Severe infections could result in a high fever, neck stiffness, disorientation, possibly coma, tremors or even death, according to Vector Disease Control International.

The VDCI also says that, as of today, there is still no cure for the virus, but treatment can include hospitalization, IV fluids and respiratory support.

In 1930, St. Louis had a population of 821,960 based on US census data collection, and about 328,500 of these citizens had a case of the virus, most without symptoms, according to the National Library of Medicine.

The city of St. Louis was included in the name of the virus after a widespread outbreak that was first identified in St. Louis in 1933, according to the Cleveland Clinic. During the outbreak, more than 1,000 clinical cases were reported, resulting in 201 deaths. An agent from this outbreak carried on and became known as St. Louis encephalitis.

As of June of last year, the virus was reported to have spread to Nevada. the Southern Nevada Health District reported that its Mosquito Surveillance Program detected two mosquito pools, comprised of 46 mosquitoes from two Nevada zip codes. They tested positive for the virus that causes St. Louis encephalitis, according to KLAS, Nexstar's Las Vegas affiliate.

As mentioned, there’s no cure, so the best practice is to prevent bites. To do that, the CDC recommends wearing insect repellent, wearing long-sleeved clothing, treating clothing and taking steps to control mosquitos indoors and outdoors. 

Experts from the Sophia M. Sachs Butterfly House say that while we may not enjoy mosquitoes and do want to avoid being bitten, we still need them in our ecosystem, since they are food for pollinators like birds and bats, and they are pollinators themselves.

The Butterfly House recommends going fragrance-free and using box fans as additional methods to deter mosquitoes. Standing water should also be removed to keep them from breeding. Not all mosquitoes bite humans, but tracking bites is important for monitoring mosquito activity.