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Member Research & Reports

Member Research & Reports

Johns Hopkins: When Mosquitoes Are Biting During Rainy Season, Net Use Increases, Study Finds

The more rainfall a region in sub-Saharan Africa gets, the more mosquitoes proliferate there and the more likely its residents will sleep under their insecticide-treated bed nets to prevent malaria transmission, a new study from the Johns Hopkins Center for Communication Programs (CCP) suggests. CCP is based at the Johns Hopkins Bloomberg School of Public Health.

While it has become clear in recent years that net use is higher in the rainy season than in the dry season, the results, published last month in the American Journal of Tropical Medicine and Hygiene, are the first to quantify this phenomenon. This new data will allow malaria control programs to see what times of year net use is lagging and use the information to intensify behavior change messages to boost net use before malaria transmission peaks, even if it doesn’t seem like the mosquitoes are biting yet.

“What we are seeing by studying rainfall patterns is that in places with year-round rainfall, which means year-round malaria transmission, people who have bed nets are using them all year, which is great news,” says CCP’s Dr. Hannah Koenker, who led the study.

In countries with a dry season, the new data show that net use peaks six to eight weeks after rains begin, which corresponds with the time it takes mosquitoes to breed and build up their populations. Malaria transmission can happen before then, however. “By better understanding seasonal patterns of net use, we can make more informed decisions about how to most effectively deploy nets and when it makes sense to heavily promote their use,” she says.

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