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A volunteer helps residents at a Covid-19 testing site in Jiangning district of Nanjing, on Thursday. Photo: Xinhua

Coronavirus: Nanjing cluster jumps to highest daily infections in China in months

  • The Nanjing cluster – now at 106 cases – is the second most serious outbreak in China since February, with most cases Delta variant infections
  • Molecular virologist suggests vulnerable and exposed populations be given a third booster dose of vaccine to save lives
The number of Covid-19 cases in Nanjing in the eastern Chinese province of Jiangsu has risen rapidly over the past week, with daily infections reaching the highest in China since February.
Jiangsu had 39 cases on Monday and a further 31 cases on Tuesday, bringing the total case number in the cluster to 106, with six asymptomatic infections. Most cases in the cluster are Delta variant infections.

The Jiangsu cluster is the second most serious outbreak in China since February, following 170 cases recorded in Guangdong in June.

“The number of cases reported has climbed recently,” deputy director general of the Nanjing Centre for Disease Control and Prevention Ding Jie said on Tuesday. “Early cases transmitted among aircraft cabin cleaners quickly and spread further through social activities and work environment contamination.

“We tracked down a large number of close contacts and have been testing them. New cases are constantly being discovered.”

On Monday, China hit a half-year high after recording its highest number of daily coronavirus cases since January, with 36 imported cases reported in the capital and in five provinces, including Yunnan and Guangdong.

“The Delta strain is more transmissible, more adapted to humans and faster to replicate. Patients have a higher viral load, take longer to treat and recover and are more prone to severe illness,” Ding said.

The city had launched a second round of mass testing while some high-risk areas had started their third, she added.

“We race against time with the virus, with measures to trace the source of the outbreak and contacts of patients, and manage close contacts and key groups. All measures have to be faster and stricter,” she said.

The cluster in Nanjing broke out last week with more than a dozen cases reported by Thursday, most of whom were cleaners at Nanjing Lukou International Airport.

In addition to Jiangsu province, cases related to the cluster have been found in Guangdong, Liaoning, Anhui and Sichuan.

Why is the Delta coronavirus variant quicker to make people sick?

On Monday, Dalian in the northeastern province of Liaoning uncovered three asymptotic patients during Covid-19 testing required for air passengers who had been to Nanjing airport. Health authorities said the infected travellers were in transit at the airport for two hours on July 17.

The Delta variant has swept across more than 120 countries. It has been found to be more transmissible than previous variants and those infected need to have a higher level of antibodies to overcome it compared to the Alpha variant, according to the World Health Organization.

The variant was at the centre of an outbreak in the southern Chinese province of Guangdong that erupted in mid-May. Guangdong reported 170 cases between May 21 and June 21.
In a preprint paper published on this month, researchers in China said the viral loads of the Delta variant grew more rapidly inside the body and caused a person to shed as much as 1,260 times more virus than the original strain last year.

The variant was also quicker to reach a detectable level once a person was infected – all adding up to a much more transmissible strain, they said.

Jin Dong-yan, a molecular virologist at the University of Hong Kong, said there were no signs of superspreading of the virus in China yet, but people of higher risk – such as physicians and airport workers – should be given a third booster dose of vaccine.

“Third injections should be implemented as soon as possible and that could save more people,” he said, pointing to a preprint paper on Sinovac’s vaccine.

China’s rebuff of WHO’s new coronavirus investigation alarms experts

The study, which has not been peer reviewed, showed that antibodies triggered by the Chinese vaccine declined below a key threshold from around six months after a second dose for most recipients, but a third shot had a strong booster effect.

“A third dose of CoronaVac administered six or more months after a second dose effectively recalled a specific immune response to Sars-CoV-2, resulting in a remarkable increase in antibody levels,” the researchers in China said.

Nationwide, China has administered more than 1.5 billion doses of Covid-19 vaccine, or more than 107 doses per 100 people.
This article appeared in the South China Morning Post print edition as: Nanjing gripped by ‘race against time’