Pupils at two public schools in Rutland are being tested to see if a new strain of flu virus has hit the area.
The Fujian flu is spreading across the country
Health officials say as many as one-third of pupils at Oakham and Uppingham schools in Rutland may have contracted the Fujian flu, which originated in China.
The virus has already been detected in hospitals across the East Midlands.
Doctors say the Fujian strain is no more aggressive than other strains, and are advising vulnerable groups to have flu jabs.
The results of tests will be known later this week.
At least five children in the UK have died from the flu so far this year - with four deaths attributed to the Fujian strain.
The Fujian flu was recently responsible for Australia's biggest flu outbreak for five years.
But Public health specialist Dr Philip Monk says the public should not be unduly alarmed as Fujian is not a particularly dangerous strain.
"Young people are falling ill with this strain of flu because it is new to this country and they are not immune to it," he said.
But Dr Monk stressed that the young, old and chronically sick should seek medical advice and be vaccinated as a precaution.