Vietnam is bracing to cope with an outbreak of cholera, which has expanded to eight provinces in the north and infected nearly 60 people since the beginning of this year, a health official said Wednesday. The Ministry of Health on Tuesday sent an urgent message to provinces nationwide, requiring them to take the necessary measures to contain the outbreak, according to the director of the Health Ministry's Preventive Medicine Department, Nguyen Huy Nga.

The message urges provinces to tighten food hygiene, crack down on unhygienic food vendors, contain the outbreak and closely monitor infected people.

According to the Ministry of Health, at least 57 people have tested positive for cholera since the outbreak occurred in mid-March. Hanoi has the highest number of patients, with 29 infected.

"Uncooked vegetables are certainly to blame for the outbreak this time," Dr Nguyen Thi Tuong Van from Vietnam's National Institute of Infectious and Tropical Diseases was quoted as saying on the VnExpress news website. "It's best not to eat uncooked vegetables."

Late last year, more than 300 people were infected with cholera in an outbreak that expanded to 11 provinces in northern Vietnam, prompting local authorities to place a ban on a popular fermented shrimp paste, known as mam tom, after it was blamed for half the cases.

No one reportedly died from the outbreak last year, although health officials warned that dehydration could kill some patients if it was not treated immediately.

Cholera chiefly spreads through drinking water or eating food contaminated with the cholera bacteria.