Hong Kong health authorities suspect a part-time hotel cleaner who tested positive for a more transmissive strain of Covid-19 came into contact with traces of the virus left in a room by an infected guest and which a contractor failed to remove.
The employee was confirmed as the sole local case on Friday, which brought to an end the city’s 24-day run of zero community infections and escalated fears of an outbreak of a mutated strain of the virus given she worked at two other locations.
Additionally, health authorities confirmed 10 imported cases, the most in a single day since April 29.
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Eight of the infections involved arrivals from Britain while the remaining two came from Indonesia and Russia.
The city’s tally of confirmed cases stands at 11,938, with 211 related deaths.
The 41-year-old female cleaner worked at Bridal Tea House Hotel in Yau Ma Tei, where a domestic helper from Indonesia tested positive for the virus while undergoing quarantine. The arrival was sent to hospital on Sunday and a separate cleaning company specialising in disinfecting quarantine hotel rooms used by infected guests cleaned the room on Tuesday.
The part-time cleaner entered the room the next day as part of her regular duties and hours later underwent mandatory screening. She tested preliminary positive on Thursday and had now been classified as a confirmed case.
Both women have tested positive for the L452R mutant strain, which has been linked to several coronavirus variants, including the Delta one that was first reported in India.
Officials identified the company as Lapco Holdings. Calls to the company’s office were not immediately returned.
“The disinfecting procedure lasted less than 10 minutes. This is extremely unsatisfactory,” said government pandemic adviser Professor Yuen Kwok-yung after inspecting the site with other officials.
“Even if you use bleach diluted one part per 49, the procedure should take at least 15 to 30 minutes before the disinfection is completed, then you can rinse with water.”
The company also had used quaternary ammonium compound as a disinfectant to clean the mattress and curtains, he noted.
“The ability of the quaternary ammonium compound in killing the coronavirus is quite weak and much slower. It also cannot kill the RNA of the virus,” Yuen said.
If the genetic material of the virus was not killed, a screening could come back positive even if the virus itself was no longer infectious, he explained.
Yuen said the female employee, who had not been vaccinated, could have breathed in the traces while cleaning.
She could have either breathed in viral particles that were no longer viable or been infected with viable ones and was still in her incubation period, he noted, adding the latter possibility could explain why her viral level was unstable and she tested negative in hospital.
Yuen said all cleaning contractors must follow guidelines established by the Centre for Health Protection. He urged all hotel cleaners to undergo vaccination.
The centre’s Dr Au Ka-wing said the government reserved the right to take action against any quarantine hotels or companies that violated guidelines or contract requirements.
Dr Chuang Shuk-kwan, also from the centre, said that more than 40 people, including the worker’s close contacts and the close contacts of those people have been sent into quarantine.
Classes at the schools attended by her two children would need to be suspended until screening was carried out, authorities said.
The woman also worked as a part time cleaner at Bluejay Residences in Ap Lei Chau and at House 2, 12A South Bay Road in Repulse Bay.
Separately, some pupils began receiving their Covid-19 vaccination through school outreach services on Friday after the government authorised lowering the age of use of the German-made BioNTech vaccine to 12.
Civil service minister Patrick Nip Tak-kuen, who oversees the vaccination drive, said about 14 per cent of the population aged 12 to 15 had booked or received at least one dose of vaccine.
He added that more than 300 schools had also contacted the government to ask for vaccination arrangement.
A record 69,853 Hongkongers were vaccinated on Friday, with the number nearly equally split among people receiving their first and second dose.
Additional reporting by Sammy Heung and Kanis Leung