Five cases of the mosquito-borne infection malaria have been detected in the United States in the past two months, marking the first local spread in the country in 20 years.

Four of the cases were found in Florida, while the fifth was logged in Texas, according to the Centers for Disease Control and Prevention. The cases are believed to be locally acquired, a statement from the organization read, though the developments pose a concern for a potential rise in imported malaria cases with increased international summer travel.

Malaria, which is mostly found in tropical countries, can be life-threatening but is preventable and curable. The World Health Organization says in 2021 there were an estimated 247 million cases of malaria worldwide. Of those cases, an estimated 619,000 people died from the disease.

And it could get worse around the world, according to a scientific study published by The Lancet in 2021, which found that climate change will increase the suitability for both malaria and dengue, another mosquito-borne illness.

"Rising global mean temperature will increase the climatic suitability of both diseases particularly in already endemic areas," according to the study's authors. "The predicted expansion toward higher altitudes and temperature regions suggests that outbreaks can occur in areas where people might be immunologically naive and public health systems unprepared."

Mild symptoms of malaria include fever, chills and headaches, according to WHO, while severe symptoms can include difficulty breathing, fatigue, confusion and even seizures. However, it is preventable with medicine and taking measures to not get bit by mosquitoes carrying the organism.

The CDC said all of the recent cases in the U.S. have received treatment, "and are improving."

About 2,000 cases of malaria are logged in the U.S. each year, according to the agency. The last time mosquito-borne malaria occurred in the U.S. was in 2008, when eight cases were identified in Palm Beach County, Fla.