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CDC Announces Presence of Rare, Tropical Illness in Three Non-adjacent States and Genetic Testing Indicates There May Be a Common Source of Exposure

Microbiologists will want to take note of the CDC’s statement that the illness can masquerade as other diseases

It is the latest example of a bacterium uncommon in the United States that has infected patients in this country—one of whom has died. The three infected patients live in separate states, but genetic analysis indicates their cases may be related.

Microbiologists and clinical laboratory managers may want to read the recent official health advisory from the Centers for Disease Control and Prevention (CDC).  It announced that the Kansas Department of Health and Environment, the Texas Department of State Health Services, and the Minnesota Department of Health, were working with the CDC to investigate “three cases of Burkholderia pseudomallei (melioidosis) infections.”

According to the health alert, “Based on genomic analysis, these three cases (one male, two females; two adults and one child) may share a potential common source of exposure. The first case, identified in March 2021, was fatal. Two other patients were identified in May 2021, one of whom is still hospitalized. One has been discharged to a transitional care unit. None of the patients’ families reported a history of traveling outside of the continental United States.”

The CDC warned, “Symptoms of melioidosis are varied and nonspecific and may include pneumonia, abscess formation, and/or blood infections. Due to its nonspecific symptoms, melioidosis can initially be mistaken for other diseases such as tuberculosis, and proper treatment may be delayed.”

Microbiology Laboratories Should Be on Alert

Melioidosis is typically only seen in subtropical and tropical regions and can be highly fatal. It is unknown how the trio of patients who contracted the illness became infected, but according to the CDC the cases do appear to be connected.

“Testing suggests a common source of infection, but that source has not yet been identified,” a CDC representative told Gizmodo. “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 added.

Peter Hotez, MD, PhD

“Melioidosis is a serious neglected tropical disease of Southeast Asia, India, and Australia where it is a major cause of pneumonia, abscesses, and sepsis. The fact that it may be gaining a foothold in the US is concerning,” pediatrician Peter Hotez, MD, PhD (above), Dean of the National School of Tropical Medicine, Professor of Pediatrics and Molecular Virology and Microbiology at Baylor College of Medicine, and Director of the Center for Vaccine Development at Texas Children’s Hospital, told Gizmodo. Clinical laboratories and microbiologists will want to monitor these cases for future developments. (Photo copyright: Baylor College of Medicine.)  

Melioidosis, also called Whitmore’s disease, was first described by Alfred Whitmore, an English pathologist, in 1912 in what is now present-day Myanmar. The bacterium (Burkholderia pseudomallei) can be found in contaminated soil and water. It is predominately found in tropical climates in Southeast Asia and northern Australia and can affect humans and many species of animals.

Researchers believe the disease may be acquired through the inhalation of contaminated dust particles or water droplets, the ingestion of contaminated water or soil-contaminated food, or other contact with tainted soil, especially through skin abrasions. It is very rare to contract melioidosis from infected individuals.

Melioidosis Masquerades as Other Illnesses

The symptoms of melioidosis are wide-ranging and non-specific and can resemble those of other illnesses. In addition, there are several types of the illness, and they can each act differently depending on where the infection is in the body. The most common symptoms of melioidosis include:

Localized Infection:

  • Localized pain or swelling
  • Fever
  • Ulceration
  • Abscess

Pulmonary Infection:

  • Cough
  • Chest pain
  • High fever
  • Headache
  • Anorexia

Bloodstream Infection:

  • Fever
  • Headache
  • Respiratory distress
  • Abdominal discomfort
  • Joint pain
  • Disorientation

Disseminated Infection:

  • Fever
  • Weight loss
  • Stomach or chest pain
  • Muscle or joint pain
  • Headache
  • Central nervous system/brain infection
  • Seizures

According to the CDC, the time between an exposure to Burkholderia pseudomallei and the first emergence of Melioidosis symptoms is not clearly defined but could range from one day to many years. However, most infected individuals begin experiencing symptoms of melioidosis within two to four weeks after exposure.

Melioidosis is difficult to diagnose, and some automated bacterial reading instruments can mistake Burkholderia pseudomallei for other bacteria. It is estimated that the disease accounts for 89,000 deaths per year worldwide. Delays in diagnosis and treatment often lead to poor patient outcomes and the mortality rate can exceed 40% in some regions, Nature reported. 

The illness is typically treated with appropriate drug therapies including intravenous antimicrobial medications, such as Ceftazidime or Meropenem, followed by an oral antimicrobial therapy such as Trimethoprim-sulfamethoxazole or Amoxicillin/Clavulanic Acid. It may take several months for a patient to be cured of melioidosis, depending on the extent of the infection.

Deadly Bacterium’s Countries of Origin and Spread to the US

According to CDC data, the greatest number of melioidosis cases are reported in Thailand, Malaysia, Singapore, and northern Australia. Cases also have been reported in other Asian countries as well as Mexico and Central America.

Burkholderia pseudomallei does not occur naturally in the US, and cases of melioidosis identified in the US are usually only seen in world travelers and immigrants who come from countries where the disease is widespread. The bacterium has been found in soil in Mexico, so it is possible that it could spread to parts of the US, which has led to concern among microbiologists.

“Due to changes in weather patterns, some pathogens that normally were not present in a particular area might start causing disease,” Alfredo Torres, PhD, Associate Provost, Department of Microbiology and Immunology, University of Texas Medical Branch, told Gizmodo. “Therefore, it is important to make the health professionals aware of this pathogen and the disease that it causes, so quick identification can be done, and treatment is properly used to save lives. Without that, it might be too late for the next melioidosis patient when the proper diagnosis is done.”

The CDC has suggested that healthcare workers consider melioidosis as a possible diagnosis for patients who have compatible symptoms, even if they have not recently traveled outside of the US.

CDC Suggests Rerunning Certain Clinical Laboratory Tests

Because Burkholderia pseudomallei can be mistaken for other bacteria, the CDC also urges the rerunning of clinical laboratory tests using automated identification, especially if another bacterium that is often mistaken for Burkholderia pseudomallei is present, Gizmodo noted.

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

The CDC considers the risk of melioidosis to the public in the US to be low, and that the chances of a potential outbreak are unlikely. However, the origins of these three cases remain a mystery and warrant further investigation.

Microbiologists and clinical laboratories should be aware of and remain alert about this potentially fatal illness. It is possible that more cases will arise in the future, especially in the three states where it has already been found.

—JP Schlingman

Related Information

CDC Warns Doctors about a Mystery Bacterial Outbreak with No Clear Origin

CDC: Melioidosis

What is Melioidosis? CDC Investigates Three Cases of Rare Bacterial Infection in the US

CDC Probes How People Contracted a Dangerous Infection Found in the Tropics—without Leaving the US

Nature Reviews Disease Primers: Melioidosis

Potentially Fatal Fungus Invades Hospitals and Public Is Not Informed