Dr Chuang Shuk-kwan of the Centre for Health Protection warned that daily infections might reach 10,000 and expressed concern over the strain on the healthcare system.

“The proportion of cases involving the Omicron subvariant BA. 5 has been rapidly rising, which is possibly one of the reasons the increase in the number of infections has accelerated. Based on the current speed, it is not impossible there will be over 10,000 cases a day,” she said.

“If the upwards trend continues and affects the burden on the healthcare system, [the government] does not rule out the possibility of tightening social-distancing measures, which we do not wish to do.”

Chuang said the proportion of cases involving subvariants BA. 4 and BA. 5 had reached 40.8 per cent on Sunday, adding that overseas experience showed BA. 5 cases could account for 60 per cent or more of overall infections due to its transmittable nature.

Government pandemic adviser Professor Ivan Hung Fan-ngai said the increase in cases was expected as BA. 5 had been replacing BA. 2, the dominant strain in the city.

“Most importantly, most cases are very mild or asymptomatic. [We should] not dwell on the number of new cases but focus on the number of hospitalisations, severe cases in the ICU and deaths. Currently very stable,” he said, objecting to a further tightening of social-distancing rules as it would only delay the “inevitable” replacement of BA. 2 by BA.5.

“More than two-thirds of the Hong Kong population has been infected or fully vaccinated with three doses. [Tightening will] not have any effect on the number of new cases, just damage the economic recovery,” he said.

Fellow adviser Professor David Hui Shu-cheong also said the figure was expected as BA. 5 was more transmittable and those who had contracted previous subvariants might be reinfected.

Hui said the daily case count might pass 10,000 in the next few weeks, which Singapore had experienced, but that he was not worried public hospitals would be overwhelmed because of the high vaccination rate and the large number of previously infected people.

He said social-distancing rules could be temporarily tightened, but only if healthcare staff were under stress.

The organisers of the Sun Hung Kai Properties Hong Kong 10K Championships, scheduled for Sunday with 2,500 runners, cancelled the event on Wednesday after being told competitor numbers would be capped at 500.

The Cross Harbour Race in Victoria Harbour may also be called off, with organisers in talks with authorities to expand a similar turnout limit.

Hong Kong health authorities warn of ‘worrying’ rise in coronavirus cases

The Hong Kong Association of Athletics Affiliates (HKAAA), which is behind the 10K Championships, said: “[The turnout cap] means we cannot guarantee fairness to all runners who have registered and paid … HKAAA regretfully announces its decision to cancel the event. All registered and paid runners will be fully refunded for their entries.”

The Hong Kong China Swimming Association had scheduled the Cross Harbour Race, which dates back more than a century, for October 23 with an increased quota of 2,000 participants.

Cross Harbour Race organisers target up to 10,000 for future events

Association president Ronnie Wong Man-chiu said after meeting representatives from several bureaus on Monday that his group was told the next day that the number of participants would have to be slashed.

“If only 500 participants are allowed, it is very difficult for us to hold the race because it is not worth it. There are many things involved such as a large number of boats, manpower. If there are only 500, we will not hold the event,” he told a radio programme on Wednesday.

“The swimmers have been practising since last year. If the race is cancelled, they will be very disappointed. We hope that we can still hold the event.”

A government spokesman said the decision was made after officials considered the number of Covid-19 infections and the large amount of participants in the events.

The authorities said they were also worried about the mask-off nature of the activities, which might result in a high risk of transmission.

Wong said his association wanted to propose alternatives such as a reduction in the number of swimmers and staff to 400 and 100 respectively for each session, but maintaining the total number of participants at more than 1,000.

“[We can] divide the participants into four groups, with each consisting of participants and staff members of no more than 500 based on the [government’s] requirement. The groups can set off one after another,” he said.

He added it might not be feasible to delay the race, expressing fears that the weather would be too cold for swimmers later in the year and that the cap on turnout would still be in place.

The two sports associations later said in a joint statement that they were disappointed over the quota cut and that it had “created major issues” despite their efforts to engage in “intense” dialogues with the government.

They suggested that the authorities should develop greater transparency, as well as clearer and faster communication channels when they made public health decisions related to them.

The harbour race was first organised in 1906, but ended in 1978. It was revived in 2011 and renamed the New World Harbour Race.

After a two-year break due to the anti-government protests in 2019 and Covid-19 pandemic in 2020, the event returned in December last year with 1,500 swimmers, down from 4,000 in 2018.

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Contestants had to complete the 1km route between Golden Bauhinia Square Public Pier in Wan Chai and the Tsim Sha Tsui Avenue of Stars.

Last year’s competitors were required to have had two doses of a Covid-19 vaccine at least 14 days before the race. They also had to present a negative nucleic acid test result obtained 48 hours before the event as well as wear masks before and after swimming.

Another sporting highlight on the horizon is the Hong Kong Sevens rugby tournament, which has been approved to be held from November 4 to 6, with 34,000 to watch the event live at the Hong Kong Stadium. Spectators will be allowed drinks but cannot eat in the stands.

Other sports events include the Standard Chartered Hong Kong Marathon and Oxfam Trailwalker, both scheduled for November. The turnout for the former last year was around 18,500, while that of the latter in 2018, when it was last held, was more than 4,000.

The daily quota for entering Hong Kong through the Shenzhen Bay control point under the “Come2HK Scheme” was from Wednesday increased from 1,000 to 1,500. The daily quota of 1,000 for the Hong Kong port of the Hong Kong-Zhuhai-Macau Bridge remains the same.

The authorities said the number of applicants for quota slots to visit the city through the Shenzhen Bay checkpoint had “significantly increased”. Officials said that they would keep in close contact with mainland authorities and make adjustments if needed.

The scheme, launched last year, exempts non-residents arriving from the mainland from a mandatory quarantine.

The Social Welfare Department said all staff at care homes would be required to take a PCR test every other day from August 31, instead of once a week, in view of recent infections in the sector.

The city’s overall Covid-19 tally stands at 1,479,393 cases and 9,634 related deaths.