In a dramatic move reminiscent of the first days of the coronavirus in China some 19 months ago, flights and trains in and out of Wuhan have been halted amid a rise in COVID-19 cases linked to the highly infectious delta variant of the virus.

Authorities have also ordered mass testing in the city of 11 million, where the virus was first detected before it spread around the world. Panic-buying by worried residents followed new lockdowns there.

China's latest outbreak, which began last month, is attributed to the highly infectious delta variant of the virus that has also been rapidly spreading across the U.S., causing the return of mask mandates and new urgency around the push for vaccination. Cases over the past two weeks have climbed nearly 150% in the United States.

In total, China has confirmed 328 new locally transmitted cases since an outbreak that began last month, the state-controlled People's Daily reported. The new infections have popped up in more than 35 cities in half of the country's provinces and regions, according to The Associated Press.

At a news conference Tuesday, a Wuhan city official, Li Tao, portrayed the mass testing as a precautionary measure.

Although officially, the latest outbreak appears relatively small, health authorities have reacted aggressively in an effort to keep the virus from regaining a foothold in the country. Since Wuhan first became the epicenter of the pandemic in 2019 and early 2020, China has moved to quash outbreaks whenever and wherever they occur, quickly implementing lockdowns and mass testing.

"Viral genome sequencing found all the strains to be the highly infectious Delta variant and cities hit by the recent resurgence have promptly taken action to curb the spread of the coronavirus," People's Daily reported.

The eastern city of Yangzhou in Jiangsu province has had the highest daily count of new infections in China, with 40 newly confirmed cases there and in the neighboring city of Nanjing on Monday, according to the South China Morning Post.

With just over a dozen local cases officially confirmed, residents and tourists in Zhangjiajie in Hunan province were ordered not to leave the city and cooperate with epidemic control measures as infections also spread there, state-run Global Times reported.

A government notice said that civil servants and public school teachers in Zhangjiajie were ordered to join local epidemic control teams, the newspaper said. "[T]heir performances will be part of their career reviews," Global Times reported.

Authorities said they have administered more than 1.6 billion doses of a China-made vaccine.

Copyright 2021 NPR. To see more, visit https://www.npr.org.