The superbug gene found for the first time in the United States has health officials very worried, NBC News reported.
The gene, called mcr-1, was found in a woman from Pennsylvania who had a bad infection last month.
In her case, it was an E. coli bacteria. But scientists say this particular gene can turn up in any bacteria, including strains that are already hard to treat.
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Public health experts have been warning about antibiotic resistance for years. More than 2 million people in the U.S. are infected by drug-resistant germs each year, and 23,000 die of their infections, according to the Centers for Disease Control and Prevention.
What the CDC fears is a return to the "pre-antibiotic era," when people died by the millions from infections such as pneumonia or strep throat, from infected cuts and scrapes and after childbirth.