European public health officials are monitoring an outbreak linked to international travel on long-haul flights.

A cluster of 20 genetically linked Shigella sonnei sequence type (ST) 152 cases were first reported by the United Kingdom.

Austria, France, Ireland, and the Netherlands have also recorded genetically linked cases, suggesting a common source of infection. Austria and France have seven cases each while Ireland has three and the Netherlands has one.

Sick people reported intercontinental long-haul travel involving a single unnamed airport but to different final destinations prior to disease onset.

Of the 38 cases, 29 had recent international travel, with 22 going to countries in Asia, including Singapore, Thailand, India, Sri Lanka, United Arab Emirates, and Saudi Arabia. Four travelled to Africa and three to Australasia.

Patients had an isolation date or date of illness onset in January 2025, with the earliest case reported on Jan. 8 and latest case on Jan. 17. Of the 38 cases, 23 are female . Patients range in age from 15 to 70 years old.

The European Centre for Disease Prevention and Control (ECDC) said the common exposure is likely to have occurred during international transit, on flights operated by the same airline or with the same caterer, or at the airport.

Further cases may occur until the vehicle and source of infection has been identified and measures put in place to address it.

ECDC said it was monitoring the incident through the EpiPulse system and was in contact with EU member states.

Infection with Shigella can occur if a person ingests food or water contaminated by human feces, either via contaminated hands or objects which have been in contact with infected feces. Secondary infections are common due to the low infectious dose.

The incubation period is one to two days. Shigellosis symptoms include diarrhea that may be bloody or prolonged for more than three days, fever, abdominal pain and discomfort.

In 2022, 30 European countries reported 4,149 confirmed cases of shigellosis. For the 578 infections wher information on the suspected mode of transmission was known, transmission via food was recorded for 394 cases.