Enterovirus 71, also known as EV-71, can cause a severe form of hand, foot and mouth disease and has symptoms including fever, mouth sores and blisters.
It is easily spread by sneezing or coughing.
The World Health Organisation has said the outbreak of the virus poses no threat to China's hosting of the Olympics in August.
Nonetheless Chinese health officials have been ordered to step-up efforts to contain the outbreak.
Provincial health officials have said any cases of people contracting the disease must be reported within 24 hours.
Hospitals have been inundated with sufferers and corridors have had to be converted into wards.
The cause of the outbreak is not known.
Enteroviruses are spread mostly through contact with infected blisters or faeces and can cause high fever, paralysis and swelling of the brain or its lining.
There are no vaccines or antiviral agents available to treat or prevent the virus, but health officials say simple hygiene steps can prevent it spreading.