A more virulent subtype of the Enterovirus 71 virus, which causes hand, foot and mouth disease (HFMD), is responsible for the recent outbreak in Ho Chi Minh City that has killed nine children, local health authorities said.
Test results of disease samples sent to a Taiwanese laboratory this week showed the EV71 B2 subtype was the reason for the rising number of infected patients in the city over the last few weeks, according to the municipal Health Department.
The virus subtype is to blame for making patients' conditions worse in a shorter period of time.
An estimated 1,200 HFMD cases, including nine fatalities, have been recorded in HCMC this year.
Doctor Truong Huu Khanh of HCMC Children's Hospital No.1 said other subtypes of the Enterovirus 71 which caused the disease in previous years were more moderate than this year's subtype.
The hospital has sent more disease samples to Taiwan to test the subtypes of the virus, he added.
HFMD first hit the city in 2003. In 2007, the disease claimed the lives of 16 children.
HFMD is a human syndrome caused by intestinal viruses of the Picornaviridae family. The most common strains causing HFMD are Coxsackie A virus and Enterovirus 71 (EV-71).
HFMD usually affects infants and children, and is quite common. It is moderately contagious and is spread through direct contact with the mucus, saliva, or feces of an infected person.
It typically occurs in small epidemics in nursery schools or kindergartens, usually during the summer and autumn months. The usual incubation period is 37 days.
Typical symptoms include a fever, sore throat, and a rash may appear on the hands, feet, mouth, tongue, and inside of the cheeks.