CDC Warns Doctors About a Mystery Bacterial Outbreak With No Clear Origin

CDC Warns Doctors About a Mystery Bacterial Outbreak With No Clear Origin
A photo of Burkholderia pseudomallei cultured in chocolate agar after three days time (Photo: Todd Parker/CDC)

The U.S. Centres for Disease Control and Prevention is warning doctors about a strange cluster of illness in three states caused by a rarely seen bacteria in the U.S., one that’s killed at least one person and hospitalised two others so far. The illness, called melioidosis, can be highly fatal but isn’t normally considered contagious between people. Officials don’t know how these victims contracted the bacteria, though the cases do seem to be connected.

Since March 2021, the CDC announced in a health alert on Wednesday, at least three people in three non-adjacent states (Kansas, Texas, and Minnesota) have contracted melioidosis. The first victim, a man with preexisting lung issues, died 10 days into his hospitalisation. The other two, a woman and child, were identified in May. And while one patient has since been discharged to a transitional care unit, the other remains hospitalized.

“The CDC is working with state health officials in Kansas, Texas, and Minnesota to investigate three cases, including one death, of a rare, but serious bacterial infection called melioidosis,” a CDC representative told Gizmodo in an email.

Melioidosis is caused by the rod-shaped bacteria Burkholderia pseudomallei and can affect many species of animals and humans. Its symptoms are non-specific, resembling many other diseases, and depend on where the infection is located in the body. Most infections cause fever, for instance, but in the respiratory tract it may cause cough, chest pain, and reduced appetite. It also can spread to the bloodstream, where it’s capable of causing life-threatening sepsis, and can even reach the brain or nervous system.

Because it’s hard to diagnose melioidosis (some automated tests can even mistake the bacteria for another species, which happened in the first case), appropriate treatment is often delayed. But even with aggressive antibiotics given through IV, it’s still regularly fatal, killing between 10% to over 40% of its victims once symptoms begin. It can also lay dormant in the body, not causing illness until a person’s health declines for other reasons.

B. pseudomallei naturally lives everywhere in the soil and water of tropical environments, and that’s usually how people come into contact with it, particularly after a rainy season where the earth is disturbed. It has been known to become aerosolised and capable of spreading through the air and between animals or people, though only on rare occasions. Still, its high lethality, hard-to-trace nature, and airborne potential has led governments like the U.S. to consider it a high-risk bioterror threat, on par with other germs like Ebola, smallpox, and anthrax.

To date, according to The Centre for Food Security and Public Health at Iowa State University, the bacteria has never been found in the natural environments of North America. So when cases in the U.S are rarely identified, they’re usually traced back to travel to a country where it’s endemic. That doesn’t seem to be the explanation here, though, since none of the patients’ families had reported any travel out of the country or far from their homes lately. But the cases do appear to be linked in some way, because all three were infected with genetically similar strains of the bacteria.

“Testing suggests a common source of infection, but that source has not yet been identified,” the agency said. “CDC is working with states to assess exposures or products these individuals have in common, as well as environmental samples from the states where cases have been identified. Additionally, CDC experts are providing epidemiologic assistance to help investigate the cause of infection.”

The CDC does think there are less likely theories for the outbreak than others, though. According to William Bower, epidemiology team lead at the Bacterial Special Pathogens Branch of the CDC, the genetic analysis argues against the idea that B. pseudomallei has established a new home in the U.S., since the strains found here clearly don’t resemble strains found further south.

“At this time, there is no evidence to suggest the cases under investigation are the result of a biological attack,” he added.

Again, this isn’t the sort of disease that’s poised to become a major epidemic in the U.S., and there have been other rare cases in North America where travel can’t seem to explain what’s going on. For now, the CDC considers the risk to the public to be low. But this outbreak is a mystery that bears solving, especially if there’s a common source still around that could sicken others. Melioidosis in general is thought to be understudied and underappreciated as a source of illness. Though it’s estimated to kill at least 89,000 people worldwide every year, for instance, the toll may very well be higher.

In its alert, the CDC asks doctors to consider melioidosis as a possible diagnosis for compatible symptoms, even if there’s no travel history; it also asks them to consider rerunning tests using automated identification if they’ve come across the several other bacteria that B. pseudomallei can be mistaken for.

“CDC encourages healthcare workers to be aware of the potential for more cases and to report cases to their state health departments,” the CDC said.