Medical staff in Tianjin carry test tubes at a temporary test site in Tianjin. Photo: People's Daily

While COVID-19 epidemic could rebound in some places in China, with at least three Chinese cities - Shanghai, Tianjin and Inner Mongolia's Manzhouli in North China - reporting COVID-19 infections in recent days, Chinese experts assured the public that the experience China has accumulated since earlier outbreaks this year would help the country cope with risk of a possible second wave of the epidemic mainly caused by imported goods. 

According to latest reports, Shanghai reported two new local COVID-19 cases on Sunday and one on Saturday. The Saturday's case was detected from the screening of 15,416 close contacts. 

Since North China's Tianjin Municipality began large-scale testing on Saturday morning, it has tested about 2.24 million residents in the Binhai New District. According to Tianjin authority,  recently 10 local infections were found, eight of whom were linked to Tianjin's Binhai new area.

Meanwhile, Manzhouli, China's largest land port bordering Russia and Mongolia, has entered into a quasi-lockdown mode on Sunday, with 300,000 local residents receiving nucleic acid tests after two local COVID-19 infections were reported on Saturday whose sources of infection remain unclear. 

The Global Times found that some cases in the recent domestic infections are more or less linked to overseas outbreak, either through cold-chain products or non-cold-chain imported routes. Tianjin's infections had a close link with an employee working at a frozen food storage plant, and Shanghai's infections started with a security inspector working at the Pudong International Airport, who had no contact history with frozen imported goods.

While the novel coronavirus is still raging in foreign countries and imported goods continue to be transported to Chinese ports, it is difficult for China to eradicate the virus, especially as winter arrives, Chinese observers said, noting that China's established anti-epidemic mechanism can curb the virus spread to a controllable level despite the risk of sporadic outbreaks.  

Chinese experience

Zeng Guang, chief epidemiologist of the Chinese Center for Disease Control and Prevention, told the Global Times on Sunday that unlike some foreign nations that have adopted loose epidemic response measures, China has a very ambitious aim, which is to bring infections to zero. 

China's anti-epidemic policies have protected many cities from becoming victims of the virus, which is the factual evidence of the effectiveness of Chinese experience in the battle against the deadly virus, Zeng noted.

But we cannot deny that since Wuhan was cleared of COVID-19 infections on March 18, infections have continuously been found in Chinese cities, including Beijing, Dalian, Kashi of Xinjiang and now in Tianjin, Shanghai and Manzhouli of Inner Mongolia, he added. 

"We cannot stop the virus from coming into our lives, but China can do its best to protect as many citizens as possible from being infected," said Zeng. At first, China had to lock down an entire city to control the outbreak, then the epidemic had regional clusters and now it is spreading sporadically. 

"The Chinese way of controlling the epidemic means once there is an outbreak, the local government could immediately mobilize entire social resources to detect the scope of infections and reduce the transmission risks," Zeng said. 

Due to the differences in outbreak scope and social environment, Chinese cities did not follow an absolutely one-size-fits-all "anti-epidemic route", but have the capabilities to limit the spread of the epidemic to its lowest range with different measures fitting local conditions, Chinese observers noted. 

The COVID-19 cases were recently found in Pudong district of Shanghai, but it had little impact on the whole city, and the Pudong district didn't adopt district-wide lockdown or mass testing for COVID-19. "The case in Shanghai proves that if we stay ahead of the virus, the cases could be detected at an early stage and the close contacts of the patients will be confined to a limited area," Zhang Yuexin, a Xinjiang-based expert specializing in infectious disease, told the Global Times on Sunday.

But the scenario in North China's Tianjin and Manzhouli is different, where massive nucleic acid tests were carried out.

According to Tianjin's local authority, most of recent new cases are direct close contacts of a previous infected person who worked at a cold-storage plant. Experts said the case hints at possible community transmission.

The source of infections in Manzhouli is still unclear and the two patients had no direct contact with imported goods, as the epidemiological studies showed.

Zhang explained that when the transmission scope or sources of infection are not clear, timely mass nucleic acid testing would help the health authority to get the whole picture of the outbreak and handle it with relevant measures. 

Asked whether it is a waste of resources as some foreign media have claimed, Zhang rebuffed the claim, saying "the cost of nucleic acid testing is much smaller than that caused by a widespread epidemic." 

Tianjin tested 2.24 million residents in the Binhai New District in one day since the large-scale screening started on Saturday morning. Manzhouli vows to finish the large-scale nucleic acid testing of about 300,000 people over three days, the city government announced Sunday.

Previously the city of Kashi, Northwest China's Xinjiang Uygur Autonomous Region, went through a sudden spike of COVID-19 infection cases in late October. The city tested all 4.7 million residents in merely four days, and later three more rounds of free nucleic acid testing were carried out to track down potential silent carriers in the city.

In mid September, after two people who crossed the Chinese border illegally from Myanmar were confirmed to be infected with COVID-19, the China-Myanmar border city of Ruili in Southwest China's Yunnan Province banned any outside vehicles or people from entering at least eight prefectures and 25 counties. A citywide testing program was finished in just four days. 

"These Chinese experiences assure Chinese citizens that an outbreak of the previous Wuhan scale will not reappear in the country," Zhang told the Global Times.

More to do 

While cases of Tianjin and East China's Qingdao have proved that imported frozen food could infect human beings, experts said the imported non-cold-chain products also carry high risks of spreading the virus. 

Two of three infected cases reported in Shanghai on Friday and Saturday  are respectively a security inspector and freight loader working at the Pudong airport, both of them with no contact history with cold-chain products. 

The Xinjiang-based expert also revealed to the Global Times on Sunday that the previous Kashi epidemic linked to a clothing factory in Shufu county was likely caused by virus imported from a foreign country via cargo transportation. That's also a case of infection through non-cold-chain imported goods. 

"Ports in Xinjiang have been strictly guarded but it is possible that international non-frozen chain cargo containers are contaminated given the prevalence of the epidemic overseas," Zhang noted.

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, also told the Global Times that as winter comes, all of the international freight environment will become similar to that of the cold chain. 

Low temperatures in winter can prolong the survival time of the virus in containers, and increase the risk of infection when people come into contact with items in the frozen environment, Wu said. 

Chinese experts suggested increasing testing frequency on staff working in high-risk areas, such as ports and airports, whether they are working at posts related to imported cold-chain goods or not.

If those people can be frequently tested and quarantined after their working shifts, just like how hospitals prevent infections, the chance of them causing domestic infections would largely reduce, Zhang said. People working at hospitals would be tested every three or seven days, and when they are off work, they would be in quarantine at designated places.