Hong Kong hygiene authorities carry out anti-mosquito operation after insect tests positive for Japanese encephalitis

Southern house mosquito in northeast New Territories found to be carrier of disease, which can be deadly especially for children

PUBLISHED : Friday, 05 August, 2016, 6:19pm
UPDATED : Friday, 05 August, 2016, 6:21pm

Hong Kong’s hygiene authorities carried out an anti-mosquito operation in the northeast New Territories on Friday morning after a species of the insect in the area was found to carry a deadly virus.

The Food and Environmental Hygiene Department found that a sample of the adult southern house mosquito collected in Tung Fung Au in Ta Kwu Ling on June 23 tested positive for the Japanese encephalitis virus, which can prompt fever, headache and an impaired mental state, and in worst case conditions coma, paralysis and even death, especially among children.

The disease is transmitted by bites from infected mosquitoes.

Specialists said it was the first time that the virus had been found in Hong Kong in the southern house mosquito, or Culex quinquefasciatus.

They said compared to other species previously known to carry the virus, this type was more common, especially near places with muddy or dirty water such as gardens, parks and construction sites. They urged residents living or passing these areas to take extra precautions.

A department spokesman said: “Although [the virus] was detected ... it does not mean that such mosquitoes can spread the disease in the territory.”

He said positive test results were not surprising from time to time as mosquitoes may acquire the virus from birds and pigs, which are known to host the virus.

Two cases of Japanese encephalitis were reported last year, according to government figures, but no fatalities were recorded. There were no human cases in Tung Fung Au last year, but there are three pig farms within two kilometres of the place where the infected sample was collected.

Dr Owen Tsang Tak-yin, a member of the Hong Kong Society for Infectious Diseases, said the government should keep a close eye on the development.

But Tsang said the maximum annual number of cases of the disease reported in Hong Kong was six and that only one in 300 to 1,000 people carrying the virus would develop more serious symptoms. He added that there should be a detailed study to determine the risk level after the discovery.

Among those who develop more serious symptoms, one in three could die or have serious brain damage, Tsang said.

He said the species, although more common in the New Territories, could also be found in many urban areas, especially where there was an accumulation of dirty water.

The department spokesman said the Centre for Health Protection would issue a letter to all doctors and private hospitals to alert them about the latest development and to remind them to report any suspected cases for follow-up action.

“Officers will also inspect pig farms in the area and provide relevant information and eduction on the prevention and control of mosquitoes,” the spokesman said.

The government started a surveillance programme on the disease last year. It covers Yuen Long, Tuen Mun, Sai Kung, North District, Sham Shui Po, Southern District and Kwai Tsing.

About 600 adult mosquitoes were collected from October last year to June. All tested negative except for the mosquito from Tung Fung Au.