But that second wave soon abated as Beijing acted quickly with targeted lockdowns and other measures. The Chinese capital saw a total of some 330 cases linked to the Xinfadi market outbreak at the end of the month when daily cases fell to single digits.
By contrast, other countries in the region are facing continued spikes following a loosening of months-long shutdowns of varying severity to contain the virus.
What the country did right in managing the virus could have valuable lessons for others in the region now battling resurgences.
"China has not seen the kind of surges in other countries mainly because of its strategy of erring on the side of caution. It has been determined to nip the surge of cases in the bud by responding swiftly once the first cases are identified," said Professor Huang Yanzhong, senior fellow for global health at the American think-tank Council on Foreign Relations, in an e-mail interview.
These measures - used in the Beijing outbreak - include lockdowns of high-risk neighbourhoods, aggressive contact tracing and quarantines, and mass testing, he added.
When the first case at Xinfadi was detected on June 11, Beijing swiftly closed the market, which houses some 8,000 stallholders and workers and is visited by thousands more daily. It also sealed off neighbourhoods near the market, and others thought to be at risk - 41 of the city's 7,000 neighbourhoods in all.
To trace residents who might have been infected either from going to the market themselves or being in contact with someone who had, the authorities used not only a health surveillance app but also teams of volunteers, community workers and government personnel to knock on doors, make phone calls or contact people on the messaging app WeChat.
Market vendors, patrons, and their contacts were the first to be tested. But tests were also expanded to include the vulnerable or easily infected such as the elderly, taxi drivers and those working in other markets. Finally, the ring fence was widened to include residents living in medium- and high-risk areas, such as where infected people live, medical workers and service sector workers. Some 2.3 million people were tested within a week.
The same graduated approach was taken to quarantines, noted an article by a group of University of Glasgow researchers in the current affairs website The Conversation.
All close contacts of confirmed cases were taken to centralised isolation sites, while self-isolation was imposed on those living in the 41 neighbourhoods deemed to be at risk.
This approach of swift, targeted action involving the key principles of tracing, testing and isolating worked. By the end of June, local cases were down to single digits and from July 7, there were no local cases.
That there have not been any major surges elsewhere in the country shows too China's effective control of its first outbreak before reopening and the care it took as it reopened to prevent surges.
As the virus began to abate significantly in March, the country began to reopen slowly, beginning with factories, some of which restarted in late February. Some cities in reopening required or encouraged employers to send their workers for testing.
Schools began reopening in April, with many cities requiring teachers and students to be tested for the virus first before they could go to school. At school, temperatures were checked, masks were mandatory and breaks staggered.
Tests were made accessible and affordable to the public. Rules on masks were relaxed in mid-May, so they are not needed when people are exercising outdoors or in well-ventilated places, including offices and schools. They are still required for hospital visits and in crowded or enclosed spaces such as lifts and subway trains.
Many cities also use a health surveillance app that shows an individual's health status, so that only when the code is green is one able to enter a shop or take a taxi, for example. The app can also track movements, so a woman who was caught in a jam in a taxi near the Xinfadi market before the outbreak was later contacted to go for a Covid-19 test. Her health app also went from green to yellow, meaning that she had to stay home.
Not all countries have the capacity to adopt all the measures taken by the Chinese government, however.
In the Philippines, for example, its early lockdowns bought it time to expand its testing capacity and treatment facilities. However, its contact tracing and suppression capacities have not kept pace with spikes in cases as the country reopened economically, said the World Health Organisation's country representative, Dr Rabindra Abeyasinghe.
If contact tracing becomes unlikely, said Prof Huang, countries should focus on other measures, such as making mask-wearing mandatory.
For China, the focus now is rebooting its economy, although it will continue to keep a wary eye on the virus and stay ready to beat it down.
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