The kinds of bacteria that can cause diarrheal ailments such as food poisoning lurk all around us. These germs, which include Escherichia coli and Shigella, can be especially easy to pick up when traveling internationally, as well as in places, such as a children's day care, that are hard to keep clean. In April the U.S. Centers for Disease Control and Prevention reported an outbreak of Shigella sonnei that has become resistant to ciprofloxacin—one of the last remaining medications in pill form that can kill that pathogen. Since then, a Scientific American investigation shows the worrisome strain is still circulating in the U.S. a year after it first emerged.

The CDC confirmed 275 cases of ciprofloxacin-resistant Shigella across the country between May 2014 and May 2015 and released somewhat more detailed data about confirmed reports in each state to Scientific American (chart below). Although these figures appear small, they almost certainly represent but a tiny fraction of the true number of ciprofloxacin-resistant cases. All Shigella infections are supposed to be reported to the cdc, but a lot of people who get sick do not go to the doctor. And those who do are sometimes not tested for the presence of Shigella, let alone drug resistance.

 
SOURCE: CENTERS FOR DISEASE CONTROL AND PREVENTION; Graphic by Nigel Hawtin