(NewsNation) — For the first time in 20 years, U.S. health officials have confirmed the local spread of malaria.

In just two months, five cases have been found in the United States — one in Texas and four in Florida.

The Centers for Disease Control and Prevention says the chance of getting malaria still remains extremely low. Nonetheless, the health agency is still warning about the potential further spread.

The CDC says all five patients have been treated and are improving.

Malaria, a mosquito-borne illness, is mostly found in tropical countries. Health officials say it’s not the number of cases that are concerning, but the circumstances surrounding them.

“What’s different about this is these (people) had not traveled and were diagnosed locally as having acquired it in Florida and Texas,” said Dr. Deb Houry, chief medical officer at the CDC.

Sandra Fisher-Grainger, president of the Florida Mosquito Control Association, said the last time a locally acquired case was identified was in 2003 in Palm Beach County.

“It’s rare,” she said.

Mild symptoms of malaria include fever, chills and headaches, according to the World Health Organization. Severe symptoms can include difficulty breathing, fatigue, confusion and even seizures. 

The CDC says about 2,000 cases of malaria are logged in the U.S. each year, but those are people who acquired it from traveling abroad.

Travel season and climate change are among the reasons scientists believe the numbers could be worse than in years past.

People can protect themselves by wearing shoes, socks, long pants and long sleeves. Mosquito repellent should be applied to bare skin and clothing.