The Hospital Authority has received five more pneumonia cases of unidentified cause, involving two men and three women. The figure brings the total number of reports to 161 since an enhanced surveillance programme began June 15.

The patients visited the Mainland and Thailand before the onset of symptoms. They are undergoing tests and the cases have been reported to the Centre for Health Protection.

The Hospital Authority boosted its surveillance programme following notification from the Guangdong Health Department of a suspected human case of avian flu in Shenzhen.

Under the programme, public hospitals report to the authority's electronic flu system all patients who have pneumonia of an unidentified cause and who had travelled to affected areas or countries with confirmed human cases of bird flu in the seven days before the onset of symptoms.