The mystery outbreak of illness at Caritas Medical Center was caused by the parainfluenza virus, the Center for Health Protection (CHP) of Hong Kong's Department of Health confirmed on Thursday.

Another patient at the hospital fell victim to the respiratory disease that day, taking the total number of cases -- including those recovered -- to 32, with two still suffering from fever.

The CHP received a report from the University of Hong Kong that three of seven patients from medical center had tested positive for the virus.

Specimens from all seven patients yielded negative results for other common respiratory diseases.

"Infections caused by the parainfluenza virus are common, especially in infants and small children. Severe illnesses, however, could occur among young children and patients with immunodeficiencies. The incubation period is generally from one to seven days," a spokesperson for the center said.

The virus is spread by respiratory secretions through close contact with those infected or with contaminated objects or surfaces.

"Infections can occur when infectious material comes in contact with mucous membranes of the eyes, mouth or nose, and possibly through the inhalation of droplets generated by a sneeze or cough."

The spokesperson said enhanced infection control measures implemented in the affected wards in the Caritas Medical Center will be effective in containing the spread of the virus. "In a hospital setting, the spread of the virus can and should be prevented by strict attention to droplet and contact precautions, such as washing hands, and wearing masks, gowns or gloves."

The center is still conducting laboratory tests on other specimens, he added.

Meanwhile, a 40-year-old man living in Ap Lei Chau has been confirmed to have contracted Japanese encephalitis, according to the CHP.

It is the fifth case in the territory but the first on Hong Kong Island this year.

The man developed a fever and saw a private doctor on November 1. He was admitted to a private hospital two days later and transferred to Queen Mary Hospital on November 5.

He now requires mechanical ventilation and is in a serious condition. He has not traveled out of Hong Kong recently, which indicates that the source of the infection is local.

Two members of his household are being monitored but have not shown signs of infection. There are about seven illegal farming sites in the Ap Lai Chau hills, which could have been a breeding ground for mosquitoes that carry the disease, according to officials.

(China Daily November 19, 2004)