Liu Minxia

    mllmx@msn.com

    SEVERAL schools in Shenzhen have been hit by Norwalk virus (Norovirus) outbreaks this month while major cities across China reported a sharper rise in cases this winter than last year, officials of the city’s center for disease control and prevention (CDC) said yesterday, inviting residents’ attention to methods of preventing and treating the seasonal affliction.

    In the past three weeks, several kindergartens and primary schools in Luohu, Nanshan and Bao’an districts reported Norovirus outbreaks, Ma Hanwu, deputy head of the CDC, told reporters yesterday, declining to specify the number of the schools or patients.

    One of the cases the center made public Dec. 2 happened in Luohu District’s Luofang Kindergarten, where 42 children and two teachers were hospitalized in the city’s first Norovirus outbreak this winter. The kindergarten suspended all classes for five days to prevent the possibility of a larger outbreak.

    The Luofang Kindergarten case was mainly caused by food contamination, while most of the other cases were caused by improper handling of the patients’ vomit, said Xie Xu, a director with the CDC’s infectious diseases department.

    Norovirus, also called the winter vomiting bug, affects people of all ages, but children are most vulnerable, said He Yaqing, a deputy director with the CDC’s clinical laboratory.

    The patients developed symptoms including abdominal pain and watery diarrhea, but the most striking symptom that Shenzhen’s younger patients exhibited this winter was vomiting, she said.

    “Norovirus becomes active every two or three years globally,” said He. “The virus is usually self-limiting, and severe illness is rare. It is not usually dangerous, and most people who contract it make a full recovery within two to three days. So there is no need to panic.”

    The virus is usually transmitted either through contaminated food or close contact with the infected, Xie said.

    Patients should be put under home quarantine for three more days after they recover, their vomit should be handled with extreme caution, and all the facilities they use should be disinfected, Xie said.

    Norovirus on surfaces can be rapidly deactivated by using sufficient heat or chlorine-based disinfectants, he said.

    “Only disinfectants containing 1,000 mg of chlorine per liter can efficiently deactivate the virus, while low concentrations of chlorine disinfectant can’t eliminate it,” he warned.

    Previous cases showed that those who take care of the patients are highly prone to the illness, and they should exercise extra caution with their personal hygiene, Xie said.

    School classes can be suspended when at least 30 percent of a class contracts the virus or when the virus spreads at a fast rate, according to Xie.

    Seafood, especially shellfish, and salad ingredients are considered the foods most often implicated in Norovirus outbreaks. Ingestion of raw or insufficiently steamed clams or oysters poses a high risk for Norovirus infection.