According to Centers for Disease Control and Prevention (CDC), multidrug-resistant intestinal illness is spreading throughout the US.

The illness called shigellosis is caused by the shigella bacteria, which is extremely contagious. Although its outbreaks are rare, health officials are concerned as this strain is resistant to the antibiotic most commonly prescribed for adults.

On Thursday, health officials said that the Shigella sonnei bacteria are causing more than 200 illnesses since last May, with large recent 45 cases in Massachusetts, 25 cases in California and 18 cases in Pennsylvania.

Many cases were traced to people who had recently traveled to the Dominican Republic, India or other countries.

Shigella causes an estimated 500,000 cases of diarrhea in the United States every year. Shigella bacteria spread very easily from person to person through contaminated food or in pools and ponds.

It can cause watery or bloody diarrhea, abdominal pain, fever and malaise, which normally develop one or two days after exposure. Doctors usually prescribe antibiotics such as azithromycin for children and ciprofloxacin, sold as Cipro, for adults.

The CDC’s PulseNet laboratory network identified increase shigella infections with an uncommon genetic fingerprint in December 2014.

Further testing at the CDC’s National Antimicrobial Resistance Monitoring System (NARMS) lab found that the bacteria were resistant to ciprofloxacin.

Since ciprofloxacin-resistant Shigella is spreading, the CDC has recommended that doctors should test for resistance before prescribing an antibiotic.

The agency suggested that people should wash hands with soap and water, especially after using the toilet and before preparing food or eating. Children should be kept home from child care and other group activities while they are sick with diarrhea.

People should avoid preparation of food for others while ill with diarrhea and also avoid swimming for a few weeks after recovering.