Seventy-four students infected with norovirus at a middle school in Anqiu, Shandong province, experienced nausea, vomiting and diarrhea on Saturday, the city's bureau of education and sports said on Monday night.

Norovirus is highly contagious and often food-borne. It is sometimes incorrectly referred to as "stomach flu" but is not related to the flu virus.

Hongyi Middle School organized medical treatment for the affected students and sent 14 to the hospital for observation and treatment.

Ten students remain hospitalized, four have been discharged, and the rest, who returned to school, no longer show symptoms.

After collecting and analyzing samples, the city's disease control and prevention center concluded that the norovirus infection, caused the illnesses.

The school in Anqiu cleaned and disinfected its facilities to reduce the risk of transmission.