A ‘Hypervirulent’ Superbug Is Spreading and Scaring Health Experts

The World Health Organization is sounding the alarm about a “hypervirulent” superbug. The agency has received increasing reports of people being infected by worrying strains of Klebsiella pneumoniae—strains that can resist the last remaining antibiotics available against the bacteria and can severely sicken anyone. Little is known about widespread or common these bacteria are, so the WHO is pushing for countries to step up surveillance of the threat.

K. pneumoniae is a ubiquitous bacterium, commonly found in the soil and as part of the human microbiota, a.k.a. the neighborhoods of harmless and beneficial bacteria that live on or in our bodies. While K. pneumoniae doesn’t usually stir up trouble when it’s living in our mouths, skin, or guts, it can sometimes spark illness, particularly when it ends up in our lungs or other parts of the body. As a germ, K. pneumoniae is typically an opportunistic infection, sickening people who are already in poor health and/or have weakened immune systems.

Like many dangerous bacteria, K. pneumoniae has steadily evolved to resist the most common antibiotics used to treat it, already making it a serious problem. But in recent years, doctors have started to increasingly come across K. pneumoniae strains that not only resist carbapenem antibiotics—potent drugs that are often a last resort treatment for superbugs—but can cause severe infections in both immunocompromised and healthy people. These strains have been coined hypervirulent K. pneumoniae sequence type 23, or hvKp ST23.

This week, the WHO issued a grave update on the situation. In light of these increasing reports, the WHO’s Global Antimicrobial Resistance and Surveillance System on Emerging Antimicrobial Resistance Reporting (GLASS-EAR) sent out a request to countries around the world earlier this year, asking whether they had spotted recent cases of hvKp ST23 in their backyard. Of the 43 countries that responded, 16 reported cases of hvKp, including the U.S., Canada, the UK, and Japan, while 12 reported cases of hvKp ST23 specifically. But even these cases are only the tip of the iceberg, given the lack of tools needed to reliably and quickly detect these infections, the WHO found.

“Globally, there is no systematic surveillance that allows for the routine identification and information collection of hvKp strains,” the organization said in its report. “Identification of hvKp is challenging given that it is determined by available laboratory capacity to perform genomic sequencing tests or analysis of specific markers that may indicate hypervirulence, so the prevalence of hvKp-associated infections may be underestimated.”

For now, the WHO has assessed a moderate risk level for hvKp ST23, while acknowledging that much more data will be needed to understand just how big of a problem it really is—and how it could become in the near future. As a result, the WHO is calling for countries to improve their surveillance efforts of hvKp strains, which should include raising awareness of it among clinicians, testing labs, and public health systems.

“WHO recommends that Member States progressively increase their laboratory diagnostic capacity to allow for the early and reliable identification of hvKp, as well as reinforce laboratory capacities in molecular testing and detection and analyses of relevant virulence genes in addition to resistance genes,” the organization said.