In 2017, more than 200 cases of “nightmare bacteria” — bacteria that are immune to most antibiotics — were identified across the US, according to the Center for Disease Control and Prevention (CDC).

But far from being the stuff of mere nightmares, these bacteria pose a very real threat to public health. The germs’ resistance to antibiotics renders many medications useless against those infections, putting the health of hundreds of thousands of Americans at risk.

"Two million Americans get infections from antibiotic resistance, and 23,000 die from those infections each year," principal deputy director of the CDC Anne Schuchat said at a press briefing on Tuesday.

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The CDC tested nearly 6,000 antibiotic-resistant bacteria sampled from hospitals and nursing homes as part of a study of drug-resistant bacteria carried out from 2006 to 2017. A quarter of the antibiotic-resistant bacteria identified were also found to have genes that help them spread their drug-resistant traits, meaning they have the potential to turn other germs into “nightmare bacteria.” Of the thousands of samples tested, 221 bacteria from across 27 different states were found to carry “especially rare resistance gene[s].”

This is the first time the CDC has tested bacteria for these rare genes, so it is unclear whether the presence of these genes has been increasing in bacteria; however, Shuchuat said she was surprised at how quickly these germ traits have already spread.

While there’s no stopping bacteria from evolving to resist drugs, isolating patients infected with “nightmare bacteria” can help slow their spread, according to the CDC. In order to effectively target these dangerous germs, there will need to be a concerted effort to identify and response to cases between health care facilities, labs, and health departments, the CDC said.

Read more: Antibiotics Are Becoming Less Effective So Canada Is Planning For Antimicrobial Resistance

CDC officials have advocated for a containment strategy, which they predict could reduce the number of “nightmare bacteria” cases by 76% within three years, in a given area, CNN reported.

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