(CNN) — There are two more cases of locally acquired malaria in Sarasota County, according to the Florida Department of Health, bringing the total number of cases to six in the state.

At the end of June, the Florida department issued a statewide mosquito-borne illness advisory following the initial four cases of malaria.

The Texas Department of State Health Services said on Friday that it is still aware of only one case of malaria there, but they are still on the lookout for other cases. Texas is also monitoring the region’s mosquito population for the disease.

These locally acquired cases of malaria are the first in the United States in the last 20 years, according to the US Centers for Disease Control and Prevention.

Malaria spreads when a female Anopheles mosquito infected with a protozoan parasite from the Plasmodium genus bites a human. Most cases diagnosed in the United States are imported. Worldwide there are about 247 million cases each year, 95% are in Africa, according to the World Health Organization. Usually when someone has a rare case of malaria in the US it is after someone has traveled to a country where malaria is more common. Only about 2,000 cases of malaria are diagnosed in the US each year.

That could change with the climate crisis. Scientists have been warning people that malaria could become more common in the US as temperatures warm.

The CDC says that the risk of locally acquired malaria is still considered extremely low in the US and that there is no evidence to suggest that the cases in Florida and Texas are related to each other.

It would be “of limited value” to test mosquitoes for Plasmodium outside the area where the locally transmitted cases have been found, the CDC says, and there’s no reason to believe other areas are at higher risk of local malaria transmission.

With the busy summer travel season, the CDC said, more people could bring the disease back to the US. The CDC encourages people to use bug spray while traveling and when at home, especially in the warmer summer months.

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