Public health measures to halt the spread of Covid-19 had an unintended consequence in Latin America and Southeast Asia in 2020: Hundreds of thousands of people were killed, according to a study published this month in The Lancet. prevent dengue virus infections. The research offers leads for new strategies to combat a dangerous tropical disease that infects more people every year.
The study found a marked decrease in infections from April 2020 in many regions where dengue fever is spread by mosquitoes; the study estimates that there were 720,000 fewer dengue cases worldwide in the first year of the pandemic due to movement restrictions.
“We’ve found really unexpected net benefits from Covid restrictions that will help us better fight dengue in the future,” said Dr. Oliver Brady, an epidemiologist at the London School of Hygiene and Tropical Medicine, the study’s senior author.
More than 5 million people around the world were infected with dengue in 2019 – also known as “dengue fever” because of the severe joint and muscle pain it causes.
dr. Brady said he and other infectious disease researchers feared disaster early in the pandemic as resources were diverted to Covid-19 and other disease control measures — such as spraying for mosquitoes — were interrupted. The huge decline in dengue cases was a happy surprise, and they were eager to find out what might be causing it. They eliminated other potential factors, including environmental changes and decreases in dengue reporting by public health authorities. That left only the serious disruption of people’s movement as a plausible explanation, he said.
School closures, in particular, appear to have played a key role in reducing dengue cases. The main dengue vector, Aedes aegypti mosquitoes, are diurnal eaters. Most dengue control programs focus on people’s homes, spraying to kill mosquitoes and checking for stagnant water that could spawn them, assuming that is where the transmission is taking place. “But if the house was the really risky place and mosquitoes just bite in the house, you’d expect stay-at-home orders to increase the risk — but we don’t see that in many countries,” he said.
The researchers are not suggesting that home orders should go ahead, but the extraordinary circumstance provided some unexpected insight. dr. Brady said their findings suggest that biting takes place in school or in the workplace, meaning mosquito control should be concentrated in public places. Dengue may also have decreased during home deliveries because when people became infected, they didn’t go outside where new mosquitoes could bite them and then pass the virus on to other people.
The dengue findings may be relevant to other closely related mosquito-borne viruses, including Zika and chikungunya, the study suggests. But dr. Brady warned that the 2021 dengue data, which should be available soon, and for a period after the pandemic, could bring bad news: the infection rate could rise back to pre-Covid levels or worse, if vector control programs were tightened. executed. disrupted, while immunity levels may have dropped because fewer people were exposed, he said.
