The number of new daily infections has been slowly going up in recent days. The number of cases reported on Sunday was the highest in a week, pushing the city’s tally of infections to 4,957, with 100 related deaths.

There were just six new infections last Tuesday and Wednesday, but the number climbed back up to 12 on each of the following two days, rising to 13 on Saturday and then 19 on Sunday.

But the health authorities said the increase in new infections could just be due to the mass coronavirus screening scheme, under which 1.71 million people had been tested and which will end on Monday.

While the Centre for Health Protection declined to say when the third wave of outbreak might end, Professor Ivan Hung Fan-ngai from the University of Hong Kong’s medical school said it could take another four to six weeks before the city returned to zero new infections on a daily basis.

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He estimated there were still around 40 to 50 hidden coronavirus carriers in the community.

“As we have reached the end of the wave, it is likely many hidden carriers may have recovered on their own so the mass testing drive may not be able to find them,” he said.

As of Sunday, 26 coronavirus carriers had been identified through the voluntary programme. Hung said the results from the scheme were within the expected statistical range.

While the citywide exercise would have been even more successful if it had come during the peak of the third wave, Hung said, it had still been useful in finding hidden carriers of the virus.

Cheung, meanwhile, wrote in his Sunday blog that the government will seek approval from Legco’s Finance Committee for the next round of coronavirus relief measures.

“The fresh round of subsidies will focus on people who have been hard hit by the social-distancing measures,” he wrote.

The government had previously announced relief measures worth nearly HK$290 billion, including a HK$10,000 [US$1,300] cash handout to permanent residents, and wage subsidies to help prop up struggling businesses.

In a separate blog, the finance chief said Hong Kong was fighting to contain the coronavirus outbreak so there would be no more infections that were untraceable.

The eradication of infections with unknown sources offered the chance of establishing a health code allowing people to travel between mainland China and Hong Kong, stimulating both economies, Chan wrote.

The government has so far approached 11 destinations, including Thailand and Japan, to discuss forming travel bubbles.

Chan added that keeping the virus under control in Hong Kong will be key to reviving the economy.

Earlier this month, the city relaxed some social-distancing measures, including increasing the limit of how many people can gather in public from two to four, and reopening venues such as beauty salons and gyms.

Chan said that restaurants, which could now seat up to four to a table, had enjoyed more business since the curbs were eased.

Both Cheung and Chan both made eleventh-hour pleas to residents to take part in the testing scheme.

“I urge all residents who have not taken the test, particularly foreign domestic workers and students, to take advantage of the last two days of testing and make a final push to break the virus’ chain of transmission,” Cheung wrote.

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Among the 19 new cases, 11 were locally transmitted while eight were imported. Of the imported cases, five were people returning from India and three were domestic workers coming from the Philippines. Authorities were unable to trace the source of infection for three of the cases, while three were detected through the testing scheme.

“The recent increase in new infections could be due to the community testing drive, even though the proportion is low, it shows there is still hidden chains of transmission,” Dr Chuang Shuk-kwan, head of the communicable disease branch at the Centre for Health Protection, told a daily coronavirus briefing on Sunday.

She said it was a positive sign that not many invisible carriers have been identified through the screening programme.

“The proportion of new cases detected is not very high, which to me is a good thing. It signifies that there are not many silent carriers in the community,” she said.

“But it also proved that there are indeed some cases in the community, and so we have to be vigilant to keep up our personal hygiene.”

Despite a rebound in new infections, she defended the government’s decision to discuss forming travel bubbles, saying discussions take time and restrictions will not be eased immediately.

Chuang declined to comment on Hung’s remarks that it will take four to six weeks for Hong Kong to return to zero daily infections, saying she had not made such forecasts. But she warned that the coronavirus was highly infectious and there were still invisible carriers in the city.

She urged citizens to keep social-distance rules, wear masks, and wash hands frequently.

Among the new cases was an Indonesian domestic worker, 41, who lived in the Lai King Disciplined Services Quarters in Kwai Chung.

Another was a self-employed delivery worker, 52, who lived in King Wing House in Tuen Mun’s Shan King Estate. He usually worked in North District.

One of the untraced cases was a 75-year-old retiree who lived in Cheung Sha Wan’s Lai Tsui Court.