Residents from the same unit number at the 40-story Yan Shek House in Shek Yam Estate have been evacuated as experts worry that drainage problems have led to the infection of six people from three flats.
Experts fear the virus was transmitted through the drainage system after an inspection of the Kwai Chung public estate yesterday found vent pipes in some units had been altered. They said they could not rule out that there are silent carriers in other units numbered 09.
Government adviser Yuen Kwok-yung from the University of Hong Kong said the three infected flats with the same number were on the 14th, 16th and 26th floors. The one on the 14th involved four patients in the same family, while there was one in each of the two other apartments.
All six patients developed symptoms between Sunday and Tuesday - which Yuen said could mean they were exposed to the same infection source transmitted through the pipes.
"We saw grass growing on the pipes on the exterior wall and found some units had altered their toilets and cut the vent pipes, indicating possible leakage," he said.
Apart from the evacuation, all residents of the building were mandated to take the virus test before Sunday.
Mandatory test notices were also issued to two other private buildings with two infected flats each: block one of The Spectra in Yuen Long and Pit Ho Building on Shanghai Street, Yau Ma Tei.
Residents were evacuated overnight yesterday at a seven-story tenement structure in Jordan that consisted of four linked buildings stretching along Reclamation Street 20 to 26. There were 29 patients from 15 units there that were infected.
As of 9am yesterday, 79 residents were sent to quarantine. Police conducted another door-to-door search operation last night to make sure all residents - mostly Nepalese who do not understand Cantonese - have been evacuated.
Chuang Shuk-kwan, the Centre for Health Protection's head of communicable disease branch, said: "The infections are widespread. There are many subdivided flats in the buildings . . . Even though some had their own toilets and kitchens, the pipes may not be up to standard."
Chuang said hygiene in common areas was undesirable.
"And as a result of the four buildings being interconnected, we want all of them to move out to cut transmission at source," she said.
Chuang said Yau Tsim Mong district saw 81 infections over the past two weeks, with some other cases scattered in the vicinity of Reclamation Street, including Shanghai Street, Temple Street, Canton Road and Woosung Street.
Initial cases emerged from construction site clusters at the Central Kowloon Route and Tseung Kwan O-Lam Tin Tunnel, with most of the patients being Nepalese, who spread the virus within their community. Authorities said they will step up health education on ethnic minorities.
The city yesterday had 29 new cases, taking the tally to 9,415, including 161 deaths. Among 26 local infections, 13 were from unknown sources.
More than 30 preliminary positive patients are pending confirmation.
