Hong Kong health authorities warned that there might be silent community transmission chains on Sunday after a preliminary positive case involving the Delta Covid-19 variant was detected in the community.
The Centre for Health Protection (CHP) reported that a 23-year-old woman who works in a Causeway Bay pet shop had tested positive with high viral load. She was suspected to be carrying the Delta variant which has been rarely seen in the city recently.
The patient developed symptoms, including a runny nose, soar throat and cough last Tuesday but did not seek treatment until Saturday, when she left a specimen for testing at a clinic in Aberdeen. She received two doses of the Sinovac vaccine on August 21 and September 16 last year, according to the Department of Health.
The pet shop employee had been to three restaurants and stayed at a hotel at Wan Chai for one night before developing symptoms. In total, fewer than 10 close contacts, including her family members, colleagues and friends who dined with her, were sent to quarantine.
Chuang Shuk-kwan, head of the CHP’s Communicable Disease Branch, said during a Covid-19 briefing on Sunday that as the new case was infected by a different variant than recently confirmed Omicron cases, “there could be another source of infection.”
“When there are untraced local cases, it means that the community contains invisible transmission chains, but we have not found them yet,” Chuang said. “If we are late to discover these cases, or she had been to high risk or crowded areas and caused transmission, the community may be at risk of an exponential growth in case numbers.”
Chuang told reporters that the Department of Health will investigate all possibilities surrounding the patient’s source of infection, including whether the disease had spread from pets to humans.
Authorities imposed an overnight lockdown and compulsory testing at the patient’s address in Aberdeen. About 55 people were tested and no positive cases were found.
This marked the city’s second untraceable local Covid-19 infection as of Monday. The other case involved a 58-year-old supermarket worker whose genome sequencing showed connections to a known imported Omicron case but authorities have been unable to pin down the route of transmission.
Cross-infection in quarantine hotel
Meanwhile, a suspected outbreak at a designated quarantine hotel in Yau Ma Tei has led to six infections and sparked concerns of local transmissions.
A 43-year-old woman who returned to Hong Kong from Pakistan on December 20 tested preliminary positive on Friday, four days after completing her 21-day quarantine in room 1206 at the Silka Seaview Hotel. The CHP confirmed her case on Sunday.
Chuang said that since she had returned home, the woman’s husband and four children had been to unspecified places in the city but the patient had not gone out.
On January 6, two men who stayed in room 1205 on the same floor at the hotel tested positive.
A similar scenario occurred on the fourth floor of the Silka Seaview Hotel, where a guest tested positive on January 10 after two people from a neighbouring room were found to be infected earlier.
Albert Au, principal medical and health officer at the CHP, said genome sequencing results for the three patients who stayed on the fourth floor were highly similar and inter-hotel transmission was suspected.
After visiting the hotel on Sunday, leading Hong Kong microbiologist Yuen Kwok-yung said that smoke tests demonstrated that air could flow from room 1205 to 1206. “If the guest was carrying the virus, in fact it is possible that when [the guest] opens the door, the virus is released to the corridor and spread to neighbouring rooms,” he said.
Yuen added that air purifiers in the hotel’s corridors were not always set to run at full power, while there were no purifiers in individual rooms, leading to insufficient air ventilation and potential hotel room cross-infections.
However, he said there were no problems regarding the hotel’s measures and drainage, therefore it could continue to serve as a quarantine facility after improvements in ventilation.
Health chief Sophia Chan announced on Monday that the quarantine period for Silka Seaview Hotel guests who stayed in neighbouring rooms to known cases will be extended, but added that she believed the hotel was still able to operate in line with quarantine requirements.
As of Sunday, the city has reported 13,041 positive cases of Covid-19 while the number of death stood at 213.
Birthday party attendees to be released
According to the Department of Health, from Monday special arrangements will be made for quarantined close contacts who test negative to leave quarantine centres early. On January 10, the CHP reduced the quarantine requirement for close contacts from 21 days to 14 days due to the shorter incubation period of Omicron.
As Monday marks 14 days since top Chinese delegate Witman Hung’s now infamous birthday party, the new measure means that close contacts who attended the event, including Secretary for Home Affairs Caspar Tsui, Director of Immigration Au Ka-wang and four lawmakers, could be allowed to leave at 11.59 p.m. on Monday, at the earliest.
After returning home, they will need to undergo seven days of self-monitoring, but they can freely leave their residence as long as they maintain social distancing and avoid social activities.