More than 50 British pupils and their teachers are being held at a hotel in China for a week, after four of the children got swine flu.
The pupils with the virus are being treated in a Beijing hospital and are said to be doing OK.
The rest of the group are staying at their hotel under quarantine, in case they spread the virus to anyone else.
The group of mostly 14-year-olds, from across England, were in China to learn about its culture and language.
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Their parents have been told that the quarantine, in a four-star hotel, should last a week.
Chinese officials said the children were being well looked after and had regular contact with their families.
Since the outbreak of swine flu began, lots of countries have been screening anyone who wants to enter their country to see if they have the virus.
That's what happened in China, when the group arrived earlier in the week, and three of the four children were found to have high temperatures.
They were taken straight to hospital where it was confirmed they had the virus. A fourth classmate fell ill later in the week.