The virus-testing scheme has become a flash point of political debate in Hong Kong, with distrust over resources and staff being provided by the China’s central government and fears DNA could be collected during the exercise.
The Hong Kong government has dismissed such concerns, saying that no personal data will be attached to the specimen bottles and that samples will be destroyed in Hong Kong after the exercise.
More than 500,000 people in the city of 7.5 million signed up for the programme in advance, and it will last at least a week.
It is aimed at identifying silent carriers of the virus – those without symptoms – who could be spreading the disease.
The government expects five million people will take part in the programme, which could be extended to two weeks depending on demand.
Hong Kong’s worst outbreak in early July was blamed in part on an exemption from quarantine requirements for airline staff, truck drivers from mainland China and sailors on cargo ships.
At its peak, Hong Kong recorded more than 100 locally transmitted cases a day, after going weeks without any in June.
The outbreak has slowed, with the city reporting just nine cases on Monday, the first time in two weeks that daily infections had fallen to single digits.
However, the government and some experts said community testing can help detect asymptomatic carriers to further stop the spread of the virus.
Respiratory medicine expert professor David Hui that even though infections have dwindled, the proportion of cases with untraceable sources of infection remain between 30% and 40%.
He said: “That means there must be some silent transmission going on, so community testing has some role in picking up these silent transmitters.
“Hopefully if we can identify these people and isolate them for a period of time that may help to break the transmission chain in the community.”
Other experts, such as Dr Leung Chi-chiu, a respiratory specialist and a member of the Medical Council of Hong Kong, said the testing programme plays only a supplementary role in controlling the pandemic in the city, due to the long and variable incubation period of the coronavirus.
Dr Leung said mass testing may not be the most cost-effective method, as it is not easy to pick up the disease in its early development, especially if a person is not symptomatic or did not have recent exposure to an infected patient.