Rise in Hong Kong coronavirus reproduction number blamed on axing of Covid-19 restrictions and waning immunity, but increase ‘expected’
- Latest figures show a reproductive number of 2.07, highest since March last year, but specialist says no cause for alarm as long as deaths, serious cases stay low
- Experts appeal to public to make sure Covid-19 and flu vaccinations are up to date as waning immunity partly to blame for reproductive number increase
The interactive web-based Covid-19 case tracker run by the University of Hong Kong revealed the real-time effective reproductive number (Rt) for city cases jumped to 2.07 on March 30, up from 1.09 on March 29.
It was the highest reproductive number since early March last year and could signal another outbreak.
The news came as Hong Kong on Sunday reported two coronavirus-related deaths and 112 new cases.
Professor David Hui Shu-cheong, a Hong Kong government pandemic adviser, said the resurgence was down to the dropping of mask-wearing and waning immunity.
“This is expected. That is why we encourage people, especially high-risk groups, to receive a booster six months after the last dose or infection,” Hui, also of Chinese University’s department of medicine and therapeutics, said.
Hui was speaking a month after the city lifted the mask mandate and other pandemic-related health precautions.
But medical experts insisted there was no need to panic as long as the number of fatalities and serious cases stayed low. They added there was no need to reinstate compulsory mask-wearing or other precautions.
Professor Ivan Hung Fan-ngai, an infectious diseases specialist at the University of Hong Kong and also a government pandemic adviser, backed Hui’s views.
“The rise in Rt is an expected normal fluctuation. Most will be very mild or asymptomatic cases. It will put no stress on the health system at all. There is nothing to worry about,” he said.
Rt is the average number of people a single patient can infect when there are no intervention measures in place.
When the value is bigger than one, it means each infected patient can go on to infect on average more than one person and the number of cases could increase exponentially over time.
If the figure is lower than one, each infected patient would go on to infect less than one person, meaning fewer people would get infected, which also suggested the transmission rate had slowed.
When it is equal to one, it means the situation has stabilised.
Mandatory mask-wearing was axed from March 1, although hospitals, clinics and care homes for the elderly or disabled may still insist visitors wear a face covering.
The government said 5.85 million out of 7.3 million Hong Kong residents had been given at least three vaccinations, with 1.11 million of them having received four.
The Centre for Health Protection last Thursday issued a flu season warning as the percentage of detections a week for seasonal influenza viruses increased from less than 1 per cent in the first week of March to 9.89 per cent in the week ending April 1.
The health watchdog also recorded a “slight” increase in new Covid-19 cases and in the per head viral load in sewage surveillance.
The centre appealed to the public to complete the recommended number of doses of Covid-19 vaccines and to get a flu shot as well.
