The Department of Health has recorded the second-highest number of hand, foot and mouth disease outbreaks in the past five years as Hong Kong enters the usual peak time for the disease in summer.
By the end of last month, 357 people had been infected in 67 outbreaks, exceeded only in the same period of 2010, which saw a particularly large epidemic.
The department's weekly Communicable Diseases Watch said most of this year's outbreaks were in childcare centres or kindergartens.
One expert said a mutation that made the disease more communicable could be the reason. 'The usual peak season for hand, foot and mouth disease is in June or July,' University of Hong Kong microbiology professor Dr Ho Pak- leung said. 'Its activity may be affected by the early arrival of the hot weather.'
The Observatory is predicting maximum temperatures above 30 degrees Celsius in the coming week.
Of those infected there were four serious cases of the EV71 virus, a common cause of the disease, one of whom had to be admitted to hospital.
Three others were affected by severe paediatric enterovirus infection and two more had echovirus 30.
Ho said the serious cases showed that none of the viruses which cause the disease should be overlooked.
'The government should monitor the viruses closely to see if there is a possibility of mutation,' Ho said, adding parents should keep an eye on their children for signs of the illness, which has no cure. 'The child usually develops fever, sores in the mouth, and a rash with blisters. But [sometimes] the sores are characterised by small red spots. It could be easily mistaken or neglected as flu.'
Outbreaks of the disease are rising elsewhere in the region this year, including on the mainland, in Taiwan and Singapore, the report said.