Authorities in China have suspended operations at a terminal in the world's third busiest cargo port after a worker was infected with the coronavirus.

The closure of a key terminal at the Ningbo-Zhoushan port on the east coast, which handled almost 1.2 billion tons in 2020, reflects China's determination to squash its worst coronavirus outbreak in months no matter the economic costs.

The worker at the port's Meishan terminal tested positive for coronavirus Wednesday, Ningbo city officials said.

The company "immediately stopped production work and closed the port area," as soon as the infection was detected, Jiang Yipeng, the CEO of Meidong Container Terminal, which operates the Meishan zone, said.

The worker had been fully vaccinated and it remains unclear how they became infected.

Meishan terminal is a newly built area of the expanded port and is its second mega-terminal, with capacity for 10 million containers, state media reported.

Almost 2,000 front-line workers at Ningbo-Zhoushan port have been placed under "closed management" -- effectively unable to leave the port -- as a result of the infection, Chinese media reported. 

Chinese port workers are routinely tested for Covid.

The latest closure threatens further disruption to the stretched global shipping network, which worsened after a typhoon hit China's east coast last month.

The global shipping network is facing its biggest stress test in memory, as soaring demand for goods from Western consumers amid the pandemic puts pressure on Chinese exporters facing strict domestic virus controls.

In May, a worker at Yantian port in the southern trade hub of Shenzhen tested positive for the virus, halting port operations for one month in a move which caused huge shipping delays.

After keeping the coronavirus largely under control since mid-2020, China is now battling its worst outbreak in months, driven by the Delta variant.

China reported 81 new cases Thursday, of which 38 were local transmissions. 

Domestic transmissions surpassed 100 on Tuesday -- the first time since January.

Officials have said many of those infected had already been vaccinated.