Four dozen British teens and three adults ended up in hospitals in Washington D.C. this past weekend during a school trip that began in New York City.

Although all of the students and adults were not exhibiting symptoms, at least a dozen were so sick with classic food poisoning symptoms that public officials in the nation’s capital decided to send the entire group to hospitals as a precautionary move, according to multiple U.S. and British media reports.

Some public health officials speculated that the illnesses could be caused by the highly contagious norovirus. Most of the British visitors, from Crookhorn College in Waterlooville, were released from hospitals without treatment. The entire group was booked into the Harrington Hotel in Washington D.C. Most had returned to their rooms there by Monday.

Hotel managers and Washington D.C. emergency officials said members of the group were already sick when they arrived at the Harrington.

A mother of one of the teenagers on the trip told The Daily Mail that the group was scheduled to fly back home tonight, arriving in England on Wednesday morning. That return trip could be delayed, the mother told the British paper. She said her daughter collapsed and has been in the hospital on IV fluids, unable to eat.

Norovirus is extremely contagious and can be spread through foods, beverages, personal contact, and contact with contaminated surfaces such as tables and fixtures in bathrooms. It usually hits within a few hours to a couple of days after exposure. Classic symptoms are severe diarrhea and vomiting, which can quickly dehydrate infected people. 

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