Just two months ago, researchers in China identified a gene that can make bacteria resistant to a last-resort antibiotic called colistin. It was a bombshell discovery for people who follow superbugs. Now that gene has been detected in at least 19 countries, and scientists are alarmed.

Colistin is what doctors give you in the U.S. when nothing else works. Because it's toxic, it can have some harmful side effects, but colistin can help defeat infections that shrug off every other antibiotic in their arsenal. If bacteria resist everything, including colistin, you're out of luck.

A map detailing where colistin-resistant bacteria have been detected.

Source: Carmen Cordova/Natural Resources Defense Council

Since the paper identifying colistin-resistant E. Coli in China was published in the the Lancet Infectious Diseases journal on Nov. 18, the gene has been detected in 19 countries in bacteria from farm animals, retail meat, or humans, according to a new tally by the Natural Resources Defense Council, which advocates for reducing the use of antibiotics in farm animals. It is in Southeast Asia, Europe, Canada, and Japan.

That doesn't mean the gene, known as MCR-1, has spread to all those places in two months. Scientists are finding it retrospectively in older samples of bacteria now that they know what to look for. In Denmark, for example, the gene was found in bacteria from food inspections as far back as 2012, when the current system of monitoring was started.