COVID-19 Delta Variant Reaches Wuhan as China Battles Widest Outbreak Since Disease Emerged in 2019

China is confronting its broadest Covid-19 outbreak since coronavirus first emerged there in late 2019, with the delta variant spreading to places that had been virus-free for months, including the original epicenter of Wuhan.

Delta has broken through the country’s virus defenses, which are some of the strictest in the world, and reached nearly half of China’s 32 provinces in just two weeks. While the overall number of infections—more than 300 so far—is still lower than Covid resurgences elsewhere, the wide spread indicates that the variant is moving quickly.

It’s the biggest challenge to China’s strategy since the virus was first detected in Wuhan, the central Chinese city that saw the world’s first lethal outbreak. The country’s strict anti-virus measures, which include mass testing as soon as a case appears, aggressive contact tracing, widespread use of quarantines and targeted lockdowns, have crushed more than 30 previous flareups over the past year.

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The arrival of the more infectious delta variant, however, is testing even that approach. The new strain may be exploiting an easing off in masking and social distancing in some places, since much of the country has been Covid-free for months. That, along with increased travel for summer vacation, created an environment where delta could gain a foothold.

China reported 99 infections on Monday, including 44 who tested positive but have no symptoms. Later in the day, seven more people were found to be infected in Wuhan, plus another in Beijing. By number of cases, it’s the biggest outbreak since a flareup in Hebei province in northern China in January, when 2,000 people were infected.

The broad spread is even more concerning, given the rise of cases in the highly protected capital and in Wuhan, whose virus-free status has been a source of pride in China. The seven new cases there are the first since China brought its original wave under control by locking down the city of some 11 million and the surrounding Hubei province.

Pang Xinghuo, the deputy director of Beijing’s Center for Disease Prevention and Control, pleaded with visitors to the city who have traveled from high-risk areas within China or suspect that they might have been in close contact with someone infected to report to authorities. Officials also urged residents to curb their travel and remain in the city for the near future if possible.

“Cluster outbreaks have occurred one after another around the country and multiple cases have been reported in Beijing, leading to a critical phase in our epidemic response,” Pang said. “We can’t let loose a single strand of risk and hidden danger.”

The initial delta infection arrived via an overseas flight from Moscow into the eastern Chinese city of Nanjing in mid-July, and spread on to a group of airport cleaning staff. Within weeks, cases have also popped up as far away as Hainan island in China’s south, 1,900 kilometers (1,180 miles) from Nanjing.

China’s vaccination rate is close to 60% and among the highest in the world, but it remains to be seen whether the country’s locally-developed shots can slow delta’s spread.

Delta Challenge

Most of those infected in Nanjing were immunized, and the vaccines — which have been found less effective than Messenger RNA shots in clinical trials — do appear to be providing protection, with only 4% of those infected in this current wave battling severe disease so far. Many of those have pre-existing conditions such as asthma, diabetes or high blood pressure, Guo Yanhong, an official with the National Health Commission, said at a briefing in Beijing on Saturday.

Read More: China Mulls Booster Shots For Some as Delta Variant Spreads

While all Covid vaccines are proving less effective against delta, concerns are high that non-mRNA vaccines like the Chinese ones and AstraZeneca Plc’s shot will be less able to slow transmission.

State-owned Sinopharm said its inactivated Covid-19 shot, given widely in China, is 68% effective against delta, citing a study in Sri Lanka. Sinovac Biotech Ltd., the other major Chinese supplier, said the antibodies induced by its inactivated Covid vaccine can still neutralize the delta strain in laboratory studies, the state-run Global Times reported, without providing more detail.

Delta is providing a reality check for the world, especially countries that thought they were emerging from the pandemic through virus containment or high vaccination levels. Last week, the U.S. Centers for Disease Control and Prevention reversed its earlier position and said fully vaccinated people should go back to wearing masks indoors in places where infections are rising. Australia, which like China had managed to snuff out Covid with strict border curbs, is battling its own delta-driven resurgence, with major cities back in lockdown.

Flooded City

“Delta accounts for 80% of cases in the U.S., and they re-instituted a requirement for masks,” said Wang Huaqing, chief immunization expert at the Chinese CDC, at the Saturday briefing. “That means delta’s spread is severe and personal protection can not be slackened even with vaccination.”

Adding to the concern is a separate delta cluster in the Chinese city of Zhengzhou, where hospital and cleaning staff have been infected. Cases were reported in the surrounding Henan province as well, where the ability to curb the virus’s spread may be weakened due to the fallout from torrential rain and flooding that destroyed infrastructure, killed 302 people and left 50 missing.

Residents in Nanjing, where the recent outbreak began, have been placed under lockdown. Also affected are those living in Zhangjiajie, a scenic area famous for its verdant mountain ridges, where a live outdoor performance a week ago with more than 3,000 spectators fueled the virus’s spread.

The sale of train tickets from Nanjing and Zhangjiajie were suspended on Monday, Beijing Daily reported.

Officials in Beijing — which has detected six infections so far — vowed to cut off the virus’ transmission with “fastest pace, strictest measures and the most decisive actions.”

The capital will tighten entry restrictions for those traveling from places currently battling outbreaks, and government and state company employees have been barred from leaving the city. Vigilance already has increased in many places, with security guards once again checking green codes at shopping malls and office buildings. Meanwhile, queues are growing at testing sites around the city.