He said authorities need to see if a 27-year-old man who works at the airport has spread the virus in the community, and whether a mother and her son who tested positive in the UK had caught the virus when they were in Hong Kong.
The Chinese University professor said health officials have also yet to find out if a part-time worker at a Yau Ma Tei hotel was really infected with the coronavirus or if her sample was contaminated.
The worker had cleaned a room where a previous Covid patient had stayed shortly before testing positive for the L452R mutated virus strain. But she repeatedly tested negative after being hospitalised.
The government advisor on the pandemic said a less-than-ideal cleaning routine may have led to the patient testing positive.
“The cleansing company used ammonia compound to clean the hotel room, and that is actually a sub-optimal effort. It may partially kill the virus, leaving some residual virus behind, so the test being positive could be contamination,” he said.
The 41-year-old cleaner, who had a fever after being admitted to hospital, could also be in the early stage of infection, Hui said.
He noted the SAR cannot follow the example of Singapore and give up the “zero infections” goal, if it wants to resume travel with the mainland.
He repeated his call on residents to get vaccinated, and pointed out the BioNTech jab can reduce the risk of symptomatic infection of the Delta variant by 88 percent, while there is no such data for the Sinovac jab yet.