Why it matters: A resurgence in travel could lead to more cases.
The United States eradicated malaria decades ago, but there were nearly 250 million cases of malaria worldwide by 2021, a vast majority in Africa, according to the World Health Organization. Before the Covid-19 pandemic, about 2,000 cases of malaria were reported each year in the United States, almost all in people who contracted the disease abroad, the CDC said. (Pregnant women can pass the parasites to their children, and the disease can also be spread through blood transfusions, though such incidents are rare in the United States, according to the CDC bureau says.)
But when people infected in other countries return to the United States, local mosquitoes can feed on them and pass on the parasites. “Things like this happen,” said Colin Carlson, a biologist at Georgetown University. “You expect that in a country that has achieved disease elimination. Every now and then you have reintroductions and a little bit of local transmission.”
Dr. Carlson said he didn’t think the nation was on the brink of a major malaria outbreak. But as international travel increases this summer, cases of imported malaria could increase, the CDC noted.
Background: The role of climate change is unclear.
Malaria is most prevalent in warm climates, and some Anopheles mosquitoes have already expanded their range in ways consistent with climate change, Dr. Carlson in a recent study.
But it’s hard to say whether the new cases in the US are related to climate change. It’s possible that weather conditions in the southern United States have become more conducive to malaria transmission, but the region was already warm enough for the disease to spread, Dr. Carlson up.
Still, climate could be contributing to these cases in more nuanced ways, he said, perhaps making the disease more prevalent in places where Americans travel. That could result in more imported cases, giving the parasites more opportunities to spread within the United States.
“If travelers return from places that are on the frontline of climate impacts, there will only be more opportunities for malaria transmission,” said Dr. Carlson. “We live in a connected world and the effects of climate change in other countries can be health problems in our country.”
What’s Next: Officials will monitor more cases.
The CDC is working with state health authorities to investigate the new cases. Officials are actively monitoring more potential cases and are working to control local mosquito populations, the agency said.
People can protect themselves by using insect repellents, wearing long pants and long sleeves, and using window screens, among other things. Those planning to travel should research the risk of malaria at their destination and talk to their doctors about preventive measures, the CDC said.
