The Hong Kong Centre for Health Protection (CHP) of the Department of Health is investigating a suspected case of Japanese encephalitis (JE) involving a five-year-old boy living in Lau Fau Shan.
Laboratory tests are being performed to confirm the diagnosis. Results of the laboratory tests are expected early next week.
As a precautionary measure, the Food and Environmental Hygiene Department (FEHD) and the Agriculture, Fisheries and Conservation Department (AFCD) have carried out vector surveys and mosquito control measures in the vicinity of the boy's residence in Sha Kong Tsuen.
According to AFCD, there are some pig farms within two kilometers of the boy's residence.
The boy, who has no recent travel history, developed fever, runny nose, sorethroat, vomiting and diarrhoea on October 16. He was admitted to Tuen Mun Hospital on October 19 and is in stable condition.
The four household contacts of him were visited by CHP's medical staff and have been put under medical surveillance. They did not have any neurological symptoms of JE. Their residence was also inspected.
The kindergarten to which the boy attended was also visited and nobody there was found to have developed JE symptoms.
Preliminary investigation does not show epidemiological linkage with the previous three local cases confirmed earlier this year.
From 1992 to 2004, there have been a total of nine sporadic cases reported in Hong Kong, comprising one local case in 1996, one imported case in 1997, one imported case in 2001, two imported cases in 2002, one local case in 2003 and three local cases so far this year.
A CHP spokesman said JE is transmitted by Culicine mosquitoes living mainly in rural areas. The mosquitoes breed in water-logged fields and marshes. The public is reminded to take measures to prevent mosquito breeding by removing stagnant water.