The U.S. Centers for Disease Control and Prevention (CDC) warned Tuesday that last year saw the identification of 221 instances of “unusual resistance genes” in germs. Of all the germ samples sent to the CDC for testing, one in four had such traits.

The CDC calls these bugs “nightmare bacteria,” and not without reason. Antibiotic-resistant germs kill 23,000 Americans each year, and they were found in 11% of people who were screened even though they showed no symptoms.

“While antibiotic resistance (AR) threats vary nationwide, AR has been found in every state. And unusual resistance germs, which are resistant to all or most antibiotics tested and are uncommon or carry special resistance genes, are constantly developing and spreading,” the CDC said in a report.

So what can people do to protect themselves? On an individual level, it’s pretty much a matter of practicing good hygiene—washing hands, keeping cuts clean, and so on.

But the real protection will need to come from speedy containment, the CDC said.

“Rapid identification of the new or rare threats is the critical first step in CDC’s containment strategy to stop the spread of antibiotic resistance. When a germ with unusual resistance is detected, facilities can quickly isolate patients and begin aggressive infection control and screening actions to discover, reduce, and stop transmission to others,” the agency said.

The World Health Organization (WHO) recommended in November that farmers and the food industry should stop pumping antibiotics into healthy animals. Farmers do this to promote growth, but the practice also helps make people resistant to antibiotics.

Meanwhile, humanity is not coming up with loads of new antibiotics to ward off the growing threat. The discovery of teixobactin a couple years back provided hope that we might have our first new antibiotic in almost three decades—work continues on using it to create a commercially viable treatment.