This past Monday, the Center for Disease Control and Prevention (CDC) reported that it was investigating four U.S. cases of melioidosis, a tropical bacterial infection rarely found in the United States.

More widespread in subtropical climates such as Southeast Asia and northern Australia, the U.S. cases this month are unique in that neither of the four patients, working with the state health departments in Texas, Kansas, Georgia and Minnesota, reported leaving the country. Usually, the CDC reports around a dozen cases of the melioidosis infection in the U.S. every year, but they tend to occur in patients who have traveled tropical areas outside of the country.

Melioidosis, which is also known as Whitmore’s Disease, is an infectious bacterial infection that may weaken the immune system. According to the CDC, it is found in contaminated soil, and is spread through humans and animals by direct contact with the contaminated area.

Health officials working with the four patients believe that they may have come in contact with an imported product or animal, but findings remain inconclusive.

The CDC , “has collected and tested more than 100 samples from products, soil, and water in and around the patients’ homes,” according to a statement released on Monday. “No samples have yet been positive for the bacteria.”

Though infectious, the CDC states that it is rare for someone to get the disease from another person. “While a few cases have been documented,” the CDC’s official website explains that, “contaminated soil and surface water remain the primary way in which people become infected.”

Signs and symptoms of melioidosis vary between the kind of infection and can be mistaken for tuberculosis and more common forms of pneumonia. A localized infection can lead to swelling, a pulmonary infection can show signs of cough and chest pain, and a bloodstream infection can lead to abdominal discomfort and joint pain. Generally, the CDC states that symptoms appear two to four weeks after exposure.

Is Melioidosis Serious?

Although the CDC has identified four cases in the United States, the Center for Disease Control and Prevention does not want the public to be worried about the unlikely widespread potential.

Two of the four patients have died while one has remained hospitalized, according to the CDC, but the fourth was released with no known risk factors for melioidosis. While previous underlying conditions can add a greater health risk, such as diabetes, liver disease, cancer, or another immune-suppressing condition not related to HIV, the CDC states that it is very rare for anyone to suffer as a result of contracting melioidosis after receiving proper medical treatment.

“People with certain medical conditions are more likely than others to get melioidosis if they come into contact with the germs that cause it,” the CDC’s official website warns, but, “there are only a few people diagnosed with melioidosis each year in the United States.”

“Person-to-person transmission risk is considered extremely low,” the statement continued, “as there have only been a few documented cases.” Healthcare personnel are also found generally not at risk as long as they follow standard precautions.

Further preventative measures and precautions have also been put in place, as healthcare works and clinicians have been asked to be aware of any acute, localized bacterial infections that may resemble melioidosis, regardless of if the patient has not traveled outside of the U.S.

Most children who get it do not carry any of the high risk factors, and the CDC’s prevention guidelines recommend standard precautions and hygiene when around standing water and agricultural soil. Notwithstanding, anyone experiencing chest pain, high fever, headache, or unexplained weight loss should still see their doctor.