One woman in Harbin, China unknowingly spread the coronavirus to more than 70 people, resulting in a fresh spate of Covid-19 infection and leading parts of the city to go under lockdown.

Harbin is the provincial capital of Heilongjiang, which has been battling a wave of new infections from across the border with Russia.

Tested negative for Covid-19 twice

The woman, a 22-year-old student whose surname is Han, returned to China from New York on March 19, Heilongjiang Daily reported.

She was placed under mandatory quarantine at home, and subsequently tested negative for Covid-19 on March 31.

After completing the 14-day quarantine, she tested negative again for the virus.

As a result, the authorities lifted her quarantine requirement on April 3.

She reportedly dined out with her family two days later, and even travelled to Shanghai on April 5, where she stayed for three days.

Harbin authorities said she infected her neighbours

Harbin health authorities said despite testing negative for Covid-19, she was carrying the virus and went on to infect her neighbours, who in turn infected others at a gathering.

One of them was a 87-year-old man surnamed Chen who had a stroke and received treatment at two of the city's largest and busiest hospitals, Financial Times reported.

This then led to infections at the two hospitals.

South China Morning Post reported that some of the man's relatives and hospital staff tested positive for the virus even without showing any symptoms.

The infection chain then spread to more than 70 people.

Patients included those from Inner Mongolia and Liaoning province, who were being treated at the hospitals, Beijing Daily reported.

Spike in domestic transmissions

On Monday, April 20, the number of domestic transmissions surpassed imported ones for the first time in China since March 12 as a result of this incident.

As of the end of Wednesday, April 22, Harbin has reported 55 confirmed cases, including an imported case.

There are also 28 asymptomatic infections, among which seven were imported.

Lockdown measures

Harbin has since imposed a partial lockdown by banning non-residents' entry to residential communities, Beijing Daily reported.

https://twitter.com/wuwenhang/status/1251998456283123712

To leave and enter their own residential zones, residents will have to show their health code to indicate their Covid-19 free status, wear masks, and have their temperature checked before entering or leaving.

Arrivals from outside China also have to be isolated upon entering the city.

No gatherings are allowed as well, with all large-scale events such as weddings and funerals banned.

In addition, Harbin residents are urged to report anyone disobeying quarantine regulations.

A reward of 3,000 RMB (S$600) is given if the information checks out.

Top image via Pear Video