According to the World Health Organization, there were 241 million cases of malaria in 2020, which led to 627,000 deaths. Of those, most were African children under age five.
At the end of July, the Incubator’s editorial and digital content assistant, Jade Lin, visited the Johns Hopkins Malaria Research Institute in Baltimore, where she learned about the science of malaria and its spread. She brings back with her greater understanding of the different ways people are fighting for global health.
Malaria is an infectious disease caused by Plasmodium parasites, which are transmitted from person to person by infected female mosquitoes. The disease occurs throughout the tropics and subtropics; however, Africa carries the overwhelming majority of the global malaria burden. Children under five are the most vulnerable to severe and deadly illness.
Around just two percent of mosquitoes carry the pathogen that causes malaria. However, in parts of Zambia, where Johns Hopkins works in partnership with the Macha Research Trust, people are contracting malaria three times yearly. The prevalence of malaria despite the low rate of infected mosquitoes is due to the sheer number of bites people are sustaining.
“We learned how infection is a game of probabilities,” said Jade. “What I found interesting was that those measures of probability can be used to get a rough estimate of transmission at the community level.”
When the rate of infected mosquitoes is multiplied by the number of mosquito bites a person sustains in a year, the product is the entomological inoculation rate—the number of infectious bites per year—which roughly corresponds to the intensity of transmission in a community.
Researchers at the Malaria Research Institute and Macha Research Trust were looking for ways to bring those numbers down through the study of mosquitoes, said Jade.
Characterizing the biology and behavior of the mosquito vectors is important for creating new interventions, understanding which may be effective, and deciding how they should be deployed. For example, the three species of mosquito most responsible for transmission of malaria all have a high preference for humans, are active at night, and rest indoors, so interventions like insecticide treated bed nets and indoor residual spraying have been highly effective. However, other species contributing to low levels of transmission are understudied and may have different behaviors. Those mosquitoes may have a different host preference or bite people outdoors. Differing adaptations, combined with lack of data, mean that it’s harder to design effective interventions.
“This example emphasized to me how science and research can inform public health efforts on the ground,” said Jade. “It was really fascinating to learn about.”
To learn more about the impacts of malaria and efforts to stop its spread, explore our Infectious Diseases Resource Pack. Harvard also has its own Defeating Malaria Initiative, which focuses on research and knowledge transfer to support the control and eradication of malaria.