The Ministry of Health has ordered health organizations across the country to strengthen prevention and control measures against norovirus infection, known as "stomach flu".

In an urgent circular yesterday, the ministry told hospitals to report abnormal increase in diarrhea cases immediately.

The circular comes after a survey showed that the rate of infection among under-5 children in 11 provinces was still 15 percent, about the average of previous years.

Also, experts warned that the illness had a high possibility of spreading across the country after recent outbreaks in Japan, Europe and the United States.

Norovirus is contagious and one of the most common gastrointestinal viruses among humans. Its symptoms include nausea, diarrhea, vomiting and abdominal cramps.

Symptoms usually appear within 24 to 48 hours of infection, and typically last for one to three days.

Monitoring should be strengthened in restaurants, schools, public places, construction sites and places migrant workers live, the circular said.

The ministry suggested that eating less raw food, especially seafood such as oysters, was the best way to avoid infection.

Despite the urgency shown by the ministry to prevent a large-scale outbreak, leading Chinese flu experts on Monday ruled out the possibility of an epidemic even though the number people suffering from colds had increased.

Survey results showed that despite a large number people suffering from colds this winter, the number of flu cases had "actually not risen" compared to the same period of previous years", said Xiao Donglou, deputy dean of Disease Prevention and Control Bureau with the Ministry of Health.

Some outpatient hospital departments, both in North and South China, have received up to 5,000 patients a day this winter, sparking concern that a flu epidemic could hit the country.

Shu Yuelong, of the National Center for Disease Control and Prevention, said the viruses that spread last winter were slightly different from those of this year.

Shu, however, warned that from December to January flu cases had seen a "rising trend" compared to October last year. But vaccinations are an effective way to avoid flu and are proving to be safe, he said.

source: China Daily/Xinhua