China: CHP reports investigation progress of case of influenza A (H9N2) infection in Hong Kong

The Centre for Health Protection (CHP) of the Department of Health (DH) in Hong Kong S.A.R(February 23) said that, regarding the human case of influenza A (H9) infection announced earlier, the subtype of the virus infected by the 22-month-old girl was confirmed as H9N2 by the Public Health Laboratory Services Branch of the CHP.

"According to the whole genome sequencing result, it is believed that the H9N2 virus isolated from sample of the patient are of avian origin. The relevant avian influenza virus showed no re-assortment with genes of human influenza origin. The CHP also found that the relevant H9N2 virus is sensitive to antiviral medicine Tamiflu." a spokesman for the CHP said.

The symptoms of the patient had subsided and is still undergoing isolation at Princess Margaret Hospital. She is now in stable condition. Also, the CHP earlier announced that one of her home contacts had presented with upper respiratory tract infection symptoms. Her nasopharyngeal aspirate sample tested negative against influenza A virus.

The CHP has already notified the health authority of the Mainland and the World Health Organization of the case. The CHP also uploaded the aforementioned genetic sequence result to the international genomic database GISAID. Epidemiological investigation of the case is ongoing.

Novel influenza A infection, including influenza A (H9), is a notifiable infectious disease in Hong Kong. Influenza A (H9N2) infection is a mild form of avian influenza. Nine cases of influenza A (H9N2) had been reported since 1999. The recent case was an imported case reported in 2020. No deaths have been recorded so far.

A stringent surveillance mechanism by the CHP with public and private hospitals, with practising doctors and at boundary control points is firmly in place. Suspected cases will be immediately referred to public hospitals for follow-up investigation.