Virus EV-71, a more virulent enterovirus, has infected more than 6,000 and killed nine children since January in Vietnam.

A 22-month-old boy has died from hand, foot and mouth disease in central Vietnam, bringing the country's death toll to nine this January, an official said.

The infant died on Feb. 14 in Da Nang city in central Vietnam, said Phi Van Kien, an official from the Department of Preventive Health and Environment.

Three other children, his preschool mates, were also suspected of contracting the virus. Local agencies have sterilized the school and surrounding areas.

The virus is transmitted through saliva, blister fluid and faeces, but it is rare among adults. Last year the hand, foot and mouth disease killed 166 people in Vietnam, mostly children.

Earlier this week the Department of Preventive Health announced that Vietnam has recorded the first human case of swine flu caused by the H3N2 virus, when a two-year-old girl in the southern province of Long An was detected with strange symptoms.

However, the department said the case is minor and her sample has been sent to the U.S. Center for Disease Control and Prevention for further tests.