Hong Kong’s daily Covid-19 caseload could surge to five digits if the more transmissive Omicron subvariants become dominant in five to 10 weeks, a health expert has warned.
But the projection was questioned by another epidemiologist Benjamin Cowling, who argued that the city’s infected population had an adequate level of immunity against subvariants.
Respiratory medicine expert Dr Leung Chi-chiu, also the former chairman of the Hong Kong Medical Association’s advisory committee on communicable diseases, said on Friday that the more transmissive subvariants BA.4, BA.5 and BA.2.12.1 had started spreading in the community, accounting for about 120 cases among the daily tally.
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The proportion of such infections has increased from 2 per cent earlier this month to 3 per cent, according to Leung.
“If these 120 cases [double] every week or two weeks ... these variants combined can possibly catch up with the number of BA.2.2 cases in five to 10 weeks,” Leung told a radio programme on Friday.
He said by that time, all subvariant cases, including the dominant BA.2.2 strain, could combine for a five-digit daily tally.
“Like in Singapore, where half of the infections are BA.5. There might be a few thousand cases of the previous strain, in addition to a few thousand cases of the new one. The daily caseload in Singapore is close to 10,000 on average,” Leung told the Post.
His estimation was based on the city’s infection count on Thursday, which at 4,375 exceeded the 4,000 mark for the first time since a rebound in June.
Thursday’s tally included 299 imported cases, with three related deaths. The city’s overall infection count stands at 1,308,954 cases, with 9,448 linked fatalities.
Dr Chuang Shuk-kwan from the Centre for Health Protection said on Thursday that although the rise in daily caseloads was not as fast as that in February and March, the numbers had doubled every two weeks.
Leung noted that the trend of rising cases had continued, with the rate of increase slowing to about 20 per cent each week instead of a weekly rise of around 90 per cent seen in early June.
He added that the large number of cases had started to affect efforts to contain the virus, with contact tracing for scheduled premises slowed down or not being done at all.
“The rebound may continue as a result,” Leung said.
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But Cowling expressed doubt on the new subvariants actually posing much of a threat to the city, where most infections involved BA.2.2.
“It seems that the people who got BA.2 are protected. They can’t [be reinfected with] BA.4 or BA.5 or BA.2.12.1 in most cases. Maybe a small number can, but mostly they can’t,” he said.
“That’s different from the situation in Europe, where there was a lot of BA.1 before BA.2. BA.1 doesn’t provide immunity against BA.4 and BA.5.”
Health authorities revealed on Thursday that there were so far fewer than 10 cases of reinfections in the fifth wave.
“Dr [Leung Chi-chiu] is correct that the number of BA.4 and BA.5 are doubling more quickly, but still not explosively, not like in Europe,” Cowling said.
“The productive number is much lower because of immunity ... We don’t really have any more stringent measures now than we did in the fifth wave, in fact it’s less.”
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