COVID-19’s impact on dengue transmission
Written by Lori Uildriks, Pharm.D., BCPS, BCGP on November 4, 2020 — Fact checked by Rita Ponce, Ph.D.
A recent study has demonstrated that physical distancing measures resulted in a significant increase in reported cases of dengue in Thailand but unchanged rates in Malaysia and Singapore.
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Dengue is transmitted to humans through the bite of certain species of Aedes mosquitos that carry one of the virus’s four serotypes: dengue viruses 1–4. These mosquitos mostly inhabit subtropical and tropical places worldwide, including some hot, humid parts of the United States.
Globally, dengue is commonplace in more than 100 countries, with 40% of the world’s population living in at-risk areas. Outbreaks of the disease are a significant health problem in the Caribbean, Africa, the Pacific Islands, Southeast Asia, the Americas, and the Middle East.
Approximately 400 million individuals worldwide contract dengue each year. About 1 in 4 people develop a resulting illness, with 22,000 individuals dying from severe disease anually.
Southeast Asia and the Western Pacific region are disproportionately burdened by dengue, with 75% of the cases arising in these countries.
In Southeast Asia, all four serotypes of the dengue virus are in active circulation, causing multiple outbreaks, which can be persistent, each year. In Malaysia, Thailand, and Singapore, the activity of all four serotypes results in substantial increases in dengue cases.
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With an initial infection, a person usually either has no symptoms or mild ones. Subsequent infections with a different serotype increase the risk of severe disease.
Severe dengue is a medical emergency and can cause internal bleeding, shock, and sometimes death.
Mild cases of dengue cause a fever accompanied by a rash, nausea, and sometimes vomiting. Often, there is pain in the muscles, joints, bones, and behind the eyes.
Warning signs of severe dengue usually begin 24–48 hours after the fever resolves. People with any of the following symptoms require immediate medical attention:
• abdominal tenderness and pain
• bleeding from the gums or nose
• vomiting three or more times in 24 hours
• agitation, irritability, or fatigue
• blood in vomit or stool
There is no cure for dengue, and treatment only addresses the symptoms. In most individuals, dengue symptoms last 2–7 days.
While there is a vaccine for dengue, the varying rates of antibodies among different populations pose a challenge to vaccination efforts.
Dengue is primarily controlled through mosquito management. This involves tracking mosquito populations, removing areas of standing water where they lay eggs, using pesticides to kill larvae and adults, and introducing mosquito predators.
Another option involves introducing mosquitoes that carry Wolbachia, a type of bacteria that blocks the insects’ ability to carry harmful viruses such as dengue.
Singapore, Malaysia, and Thailand focus on mosquito control in primarily residential areas, where the risk of exposure is highest. These countries also target high-density urban areas with the greatest incidences of dengue cases.