Public health authorities are urging at-risk residents in the Gulf Coast region of Mississippi to take extra precautions after an investigation turned up deadly bacteria living in the soil around the homes of two people who were sickened. 

The investigation was launched after two unrelated residents — one this year, and another in 2020 — were sickened by melioidosis in the area. Both are believed to have contracted melioidosis, also known as Whitmore’s disease, after they were exposed to a strain of a rare bacteria known as Burkholderia pseudomallei, which is typically seen only in tropical countries.

Though the bacteria has been found in Puerto Rico, Wednesday’s announcement marks the first time the bacteria has been discovered in the soil of a U.S. state.

Both individuals have since recovered, a spokesperson for Mississippi’s health department confirmed in an email. The CDC said in a health alert that the patients had been hospitalized for sepsis and were treated with antibiotics to battle the bacteria.

Patients typically develop symptoms an average of a week after they are exposed to the bacteria, often by touching contaminated dirt or puddles, the CDC said. 

Nicknamed the “great mimicker,” the disease is notoriously challenging for doctors to diagnose because of the wide variety of symptoms it can cause.  

Depending on which part of the body is infected, symptoms can include fever, swelling, cough, joint pain, or seizures. Any organ can be infected by the bacteria, including the brain.

Only a fraction of exposures to the bacteria — one study estimated 1 in 4,600 — result in disease. But for those who contract melioidosis, death rates can range from 10% in Australia to 35% in Thailand.

Laboratories also can struggle to accurately identify Burkholderia pseudomallei in samples collected from patients. A case in Texas from a recent unrelated outbreak was initially misidentified by scientists using an automated algorithm to investigate the sample. 

The CDC said that an average of 12 cases are typically diagnosed across the country each year, typically in people who have recently traveled to a tropical country abroad where the bacteria is entrenched in the environment. 

“Because of the identification of this bacteria on the Mississippi Gulf Coast, persons at high risk for severe infection living on the Gulf Coast should take recommended precautions,” Mississippi’s state epidemiologist, Dr. Paul Byers, said in a statement. 

The bacteria is believed to have been in the area since at least 2020 and poses a “very low” risk to the general public, according to the CDC. Many healthy people who come across the bacteria in the environment never end up with melioidosis. 

However, the two agencies say that some residents are at higher risk of severe disease and need to take precautions.

Those extra steps include avoiding mud, especially after heavy rains, and wearing gloves and boots to avoid touching soil contaminated with Burkholderia pseudomallei. 

“The most common underlying conditions that make a person more likely to become sick with or die from melioidosis include diabetes, excessive alcohol use, chronic lung disease, chronic kidney disease, and immunosuppressive conditions,” the CDC said. 

Before this year, previous hunts by public health officials had failed to turn up evidence of Burkholderia pseudomallei living in U.S. soil outside of Puerto Rico. There, scientists have previously reported the bacteria is “rare but ecologically established.”

However, there have been previous cases reported by state health departments, raising concern that the bacteria may be spreading more widely in U.S. soil. 

In 2018, a case was reported in a man in Texas who had not traveled outside the country for decades. Investigators failed to identify a source for the infection, which genomic sequencing suggested might be linked to a previous case from the same county some 15 years prior.

Four people were infected – two of whom died – in an outbreak last year. The CDC eventually linked those infections to contaminated aromatherapy sprays sold by Walmart.

The agency says it is continuing to investigate the potential spread of the virus with state health departments, which will require “extensive environmental sampling.” 

Wednesday’s announcement adds the continental United States to the list of countries that are believed to be facing endemic melioidosis, though federal scientists have estimated that the disease’s spread and toll is likely underreported around the world.

Earlier this year, the Council of State and Territorial Epidemiologists also voted to add the disease to the CDC’s list of nationally notifiable diseases for state health departments.

While it is not feasible to remove the bacteria from the soil, the agency says “public health efforts should focus primarily on improving identification of cases” for appropriate treatment.