CDC probes how people contracted a dangerous infection found in the tropics – without leaving the U.S.

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When a 63-year-old Texas man who had not left the United States in 30 years sought treatment for a fever, chest pain and difficulty breathing in November 2018, doctors discovered a surprising culprit: a bacteria that is endemic to Southeast Asia and northern Australia.

Nearly two years later, doctors and researchers remained flummoxed by the man’s melioidosis diagnosis, because nothing in his medical or personal history suggested that he had been exposed to soil or water infected with the disease-causing bacteria called Burkholderia pseudomallei.

Now, three states have launched investigations alongside the Centers for Disease Control and Prevention to discover how three more people in the United States contracted the rare and serious illness this year without traveling to the tropical climates where the infectious bacteria naturally occur.

Public health officials in Texas, Kansas and Minnesota, with the CDC, are probing melioidosis cases involving two adults and one child, according to a health advisory issued by the CDC on Wednesday. One person was hospitalized in March and died from the infection. The other two were diagnosed in May, with one of them still in the hospital more than a month later.

None of the people infected this year had recently traveled outside the country.

“These three cases are unusual because no recent travel outside the United States has been identified,” the advisory said.

The investigation comes about a year after the CDC published a case study about the Texas man diagnosed 2018, who was hospitalized but recovered after treatment. He lived on a small ranch in rural Atascosa County outside of San Antonio. The property did not have running water or a private well, so the man bought chlorinated water from the local municipal water utility and stored it in a tank that he climbed inside and scrubbed clean once or twice a month, according to a study reviewing his case.

But when researchers collected samples from the water tank and the soil around the man’s home, they failed to find the source of the rare bacteria, which hasn’t been recorded inside the continental United States.

“The source of this patient’s infection remains unknown,” researchers concluded in the June 2020 study.

They also urged further investigation because some scientists have theorized that the American southwest could have “suitable habitats for B. pseudomallei” that could allow the bacteria to live naturally in the soil.

Melioidosis infections can present like an infected wound, with swelling or ulcers at the exposure site, but they can also occur in the lungs, the bloodstream or widely spread throughout the body. People with diabetes, kidney disease, chronic lung disease, and alcoholism are more likely to develop severe infections. A wide range of symptoms, which can include fever, cough and difficulty breathing, can lead doctors to mistake the infection for other illnesses like tuberculosis or pneumonia, according to the CDC.

The confusion can be dangerous because if a patient infected with melioidosis isn’t treated with the proper medications quickly enough, the infection can turn deadly. The CDC estimates that 10 to 50 percent of melioidosis cases are fatal, depending on the level of medical care available.

Because the illness can kill without proper treatment and because the bacteria that causes the infection naturally lives in the soil in many parts of the world, officials have long monitored the potential for Burkholderia pseudomallei to be used as a biological weapon. In 2014, the bacteria was among vials of dangerous pathogens discovered improperly stored in National Institutes of Health and Food and Drug Administration labs. A year later, the bacteria escaped the Tulane National Primate Research Center in Louisiana and may have infected a veterinary clinic worker who was exposed.

Most cases of melioidosis diagnosed in the United States occur in people who have traveled to the regions where the bacteria naturally resides in the soil. An infection can occur if bacteria from the soil enters the body through an open cut or a break in the skin.

The three patients who sought treatment earlier this year reported a wide range of symptoms, according to the CDC, including cough and shortness of breath, fatigue, vomiting, intermittent fever and a rash.

The patient hospitalized in March had preexisting chronic obstructive pulmonary disease and cirrhosis, which may have exacerbated the melioidosis infection. That patient died 10 days after being admitted to the hospital, according to the advisory.

The Texas man in the 2018 case developed a lesion on his chest and experienced respiratory failure three days after being admitted into the hospital. After doctors identified the cause of the infection, he received the necessary antibiotics and began to recover.

It is not common for melioidosis to pass from person to person, and infections typically start after a person is exposed to contaminated water or soil. The CDC’s health advisory noted that a genetic analysis of the bacteria that caused all three of the 2021 cases suggests that the patients “may share a potential common source of exposure.”

“Genomic analysis of the strains suggests a common source, such as an imported product or animal,” the advisory said. “However, that source has not been positively identified to date.”