Vietnamese vegetables face high risk of catching the lethal E. coli outbreak as farmers mostly use sewage and muddy water taken from streams, lake and rivers, to irrigate the crops, a health official has warned.

Nguyen Cong Khan, chief of the Vietnam Food Administration (VFA), said the E. coli outbreak has claimed 18 lives and left more than 1,500 people sick, including nearly 400 suffering severe and potentially fatal symptoms, across Europe.

In Vietnam, eight people died and 1,513 were hospitalized from food poisoning since early this year, he said.

In May alone, 116 people were admitted to hospital in 10 food poisoning cases; four of the 10 cases are blamed on E. coli.

Experts said the food poisoning cases happened in hot weather, when the high temperature allows more bacteria to grow.

A recent survey by the VFA showed an alarming discovery that 67 percent of food industry workers in Ho Chi Minh City are infected with E. coli (on their hands).

Doctor Tran Phu Manh Sieu of HCMC Hospital of Tropical Diseases said food vendors on the street usually wash dishes in dirty water, making it easy for the food borne bacteria to pass on customers.

Frozen food like meat, vegetables and seafood in supermarkets can catch E. coli if they are not well preserved, he added.

Local experts advised people to wash their hands before eating or cooking, and to eat well-done food. Raw-serving vegetables should be carefully washed and soaked in salty water, they said.

According to the World Health Organization, most strains of E. coli are harmless but the bacteria involved in the latest outbreak, EHEC (enterohaemorrhagic E. coli), cause more severe symptoms. 

It is transmitted to humans primarily through consumption of contaminated foods, such as raw or undercooked ground meat products and raw milk. Its significance as a public health problem was recognized in 1982, following an outbreak in the US.

Fecal contamination of water and other foods, as well as cross-contamination during food preparation (with beef and other meat products, contaminated surfaces and kitchen utensils), will also lead to infection, according to WHO.