Climate change is causing a shift in weather patterns, some of which can worsen malaria conditions. A higher average surface temperature from global warming could lead to higher mosquito migration in areas that were previously uninhabitable by Anopheles mosquitoes.
`The Centers for Disease Control and Prevention reported on June 26, 2023, that five cases of locally transmitted malaria had been identified – four in Florida and one in Texas – since May 2023. These are the first cases of locally acquired mosquito-borne malaria in the U.S. since 2003.
The Conversation spoke with Dr. Rajiv Chowdhury, a global health expert from Florida International University, about the significance of these cases and why they’re appearing now.
What is malaria and how did these people become infected? Malaria is a serious and sometimes life-threatening disease caused by the bite of a female mosquito from the genus Anopheles, the vector that transmits malaria.
The most common symptoms are fever, chills, headaches, muscle aches and fatigue. These symptoms typically occur from 10 to 15 days after people are infected with the parasite. However, if untreated, more severe symptoms may appear that include impaired consciousness, difficulty breathing, convulsions, abnormal bleeding and more, which can ultimately lead to death.
The five cases in Florida and Texas were caused by the Plasmodium vivax parasite, which is the most common malaria-causing parasite strain outside of the African continent. All are believed to be locally acquired, which means they were not connected to any international travel. In addition, there is no evidence to suggest that the cases in the two states are related. Plasmodium vivax is the most globally widespread of all Plasmodium strains and can cause severe, often fatal, infections.
All five patients have reportedly recovered, and surveillance for additional cases is ongoing.
Why might these cases be surfacing now? There could be several factors driving the emergence of locally acquired malaria.
For one, climate change is causing a shift in weather patterns, some of which can worsen malaria conditions. A higher average surface temperature from global warming could lead to higher mosquito migration in areas that were previously uninhabitable by Anopheles mosquitoes.
These higher temperatures could also enhance the growth rate and transmissibility of the parasites responsible for malaria. These include Plasmodium parasite variants such as vivax, knowlesi and falciparum.
The effects of climate change can also lead to higher rainfall and sea level rise in many places – both of which can result in more areas or open spaces with stagnant water that typically serve as effective breeding grounds for mosquitoes.
Given these changes in local conditions, more cases could occur in populations that were previously “immunologically naïve” to malaria. In other words, since these people have never been exposed to it, their immune systems are ill-equipped to fight it.
Furthermore, when people travel to countries or areas where climate-driven malaria cases are on the rise, there is a greater possibility of bringing those infections back to the U.S., where local mosquitoes could be exposed to the parasite in an infected person’s blood.
Lastly, due to misuse and overuse of common antimalarial medications, such as artemisinin, antimicrobial resistance has become a major problem in many regions of the world. This drives up the number of drug-resistant cases, the severity of the illness and the possibility of larger outbreaks.
This is further complicated by emerging resistance to insecticides among Anopheles mosquitoes.