Another shipping crisis is in sight, as a virus outbreak in southern China disrupts port services and delays deliveries, driving up costs again.

The Chinese province of Guangdong has faced a sudden uptick in Covid-19 cases. Authorities have moved to shut down districts and businesses to prevent the virus from spreading rapidly.

That’s causing massive shipping delays in major Chinese ports, and jacking up already-high shipping costs as waiting times at berth “skyrocketed,” according to analysts and those in the shipping industry. 

“The disruptions in Shenzhen and Guangzhou are absolutely massive. Alone, they would have an unprecedented supply chain impact,” said Brian Glick, founder and CEO at supply chain integration platform Chain.io, told CNBC.

However, combined with the challenges that the global supply chain has faced since this year, shipping is in “absolutely uncharted waters,” said Glick. 

Guangdong, a major shipping hub, accounts for about 24% of China’s total exports. It is also home to the Shenzhen port and the Guangzhou port — which are the third largest and the fifth largest in the world by container volume, according to the World Shipping Council.