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News — No longer considered just a distant threat in tropical regions, the mosquito-borne virus Dengue fever is now making its presence felt in the U.S. Health officials have reported a concerning rise in cases of Dengue in recent months in states like Texas, Florida and Hawaii. Although the U.S. has largely been spared from large-scale outbreaks in the past, over the growing risk. The first locally acquired case of Dengue in 2024 was announced recently in Texas. With 106 travel-associated dengue cases, including one death, reported in Texas, this is the highest annual case count since 2002 in the Lone Star State.

Sasha R. Azar, Ph.D., an assistant professor and member of the Center for Tissue Engineering at Houston Methodist Research Institute, is quite familiar with the dengue viruses, and at present, he says, there are no vaccines or specific treatments for dengue infection approved in the U.S., so for those who are concerned, prevention with insect repellents, such as DEET or picaridin, or by elimination of mosquito breeding sites like standing water in and around homes are the best options.

With a background in arboviruses and mosquitoes, Dr. Azar also can discuss the following key points about dengue viruses:

• Dengue fever is caused by infection by one of the four closely related dengue viruses that are members of the viral family Orthoflaviviridae, which is a family that includes West Nile, Zika and yellow fever viruses, as well.
• Dengue is the most common arthropod-borne virus infection, with annual cases estimated at approximately 400 million, of which 20-100 million are estimated to result in symptomatic disease. The majority of infections occur in tropical and sub-tropical areas, often in regions below the equator.
• Infection generally occurs through the bite of an infected mosquito – often the yellow fever mosquito (Aedes aegypti) or the tiger mosquito (Aedes albopictus) – although infection via transfusion or transplant is possible, albeit highly unlikely given screening done prior to such procedures
• Human infection can be, and frequently is, asymptomatic. Most symptomatic cases present as a relatively mild febrile illness with symptoms such as fever, muscle aches, rash and nausea. Some patients may experience a more severe disease (classified as “dengue with warning signs") in which further symptoms, such as abdominal pain, vomiting, mucosal bleeding and altered mental status. In the most severe cases, classified as “severe dengue,” patients can experience plasma leakage, fluid accumulation and hemorrhage, as well as liver and other organ damage.
• There are four dengue viruses, and infection by one confers lifelong or near lifelong immunity to that particular dengue, such as Dengue 1 (DENV1). However, the antibodies against that specific virus are not as efficient at neutralizing the other three. A person exposed to one type of dengue who is subsequently exposed to one of the other three can present with more severe disease, a phenomenon commonly referred to as “antibody dependent enhancement.” Serious disease doesn’t only occur in the case of antibody dependent enhancement, as primary dengue infection can manifest as severe dengue, as well.
• With respect to Houston, both vectors (Aedes aegypti and Aedes albopictus) are present, but dengue itself is not endemic. However, the Gulf Coast is a sub-tropical environment that could, in theory, sustain an urban transmission cycle. Frequently, imported cases of dengue are reported in various states in the continental U.S. If a traveler who was infected while in a dengue endemic region comes to a non-endemic area with susceptible mosquitos, those mosquitos can potentially become infected and subsequently transmit the virus.
• What is critical to note is that sustained urban transmission requires many infected individuals and many mosquitoes in proximity. A few infected travelers infecting local mosquitoes is unlikely to cause a large-scale outbreak.
• -Currently, temperatures are anticipated to plummet. Aedes aegypti, in particular, do not tolerate temperatures below 50 degrees Fahrenheit well. Activity and blood feeding tend be reduced even at temperatures below 60 degrees Fahrenheit. As such, this local case is unlikely to result in appreciable levels of local transmission.

Dr. Azar is available for interviews, if you’d like to speak with someone, and I’d be glad to coordinate a time for him to chat with you. Please feel free to send me an email at [email protected] or text at 281-620-2502.