International travelers are bringing a multidrug-resistant intestinal illness to the United States and spreading it to others who have not traveled, according to a report released by the Centers for Disease Control and Prevention (CDC). Shigella sonnei bacteria resistant to the antibiotic ciprofloxacin sickened 243 people in 32 states and Puerto Rico between May 2014 and February 2015. Research by the CDC found that the drug-resistant illness was being repeatedly introduced as ill travelers returned and was then infecting other people in a series of outbreaks around the country.

CDC and public health partners investigated several recent clusters of shigellosis in Massachusetts, California and Pennsylvania and found that nearly 90 percent of the cases tested were resistant to ciprofloxacin (Cipro), the first choice to treat shigellosis among adults in the United States. Shigellosis can spread very quickly in groups like children in childcare facilities, homeless people and gay and bisexual men, as occurred in these outbreaks.

“These outbreaks show a troubling trend in Shigella infections in the United States,” said CDC Director Tom Frieden, M.D., M.P.H. “Drug-resistant infections are harder to treat and because Shigella spreads so easily between people, the potential for more – and larger – outbreaks is a real concern.  We’re moving quickly to implement a national strategy to curb antibiotic resistance because we can’t take for granted that we’ll always have the drugs we need to fight common infections.”

In the United States, most Shigella is already resistant to the antibiotics ampicillin and trimethoprim/sulfamethoxazole. Globally, Shigella resistance to Cipro is increasing. Cipro is often prescribed to people who travel internationally, in case they develop diarrhea while out of the United States. More study is needed to determine what role, if any, the use of antibiotics during travel may have in increasing the risk of antibiotic-resistant diarrhea infections among returned travelers.

“The increase in drug-resistant Shigella makes it even more critical to prevent shigellosis from spreading,” said Anna Bowen, M.D., M.P.H., a medical officer in CDC’s Waterborne Diseases Prevention Branch and lead author of the study. “Washing your hands with soap and water is important for everyone. Also, international travelers can protect themselves by choosing hot foods and drinking only from sealed containers.”