The coronavirus is set to further damage trade in the coming months, threatening supply chains and upending commerce like never before, according to the head of Europe’s largest port, Rotterdam.

“We are facing unprecedented disruptions and the port of Rotterdam, as a vital process, intends to continue contributing to society,” port Chief Executive Officer Allard Castelein said in a statement. The true impact on the decline in demand will become clear from April onwards, he said, adding that throughput at the port could slump significantly in the coming months.

Europe’s largest ports—essential to the delivery of food, medicine and other vital materials—are being tested to the limit as the outbreak consumes the continent. The challenges are myriad: preventing delays, ensuring that goods aren’t contaminated, managing congestion amid ship quarantines, and keeping their own workforce healthy.

Even at places where internal operations so far have been largely unaffected—such as at Rotterdam, where robots do much of the heavy lifting—the pain inflicted by the virus is evident. Overall throughput volume dropped 9.3% in the first quarter, compared with the same period last year, and a decline of as much as 20% on an annual basis is very likely, according to Castelein.

“This will depend on how long the measures remain in place and on how quickly production and world trade recover,” he said.

Governments across Europe are busy trying to limit the economic damage of containment measures while avoiding another surge in the spread of the disease. More than 50,000 people have died, though the number of new cases on the continent has stabilized in recent days. Germany is moving forward with plans to slowly start returning to normal, while the U.K. is expected to extend its nationwide lockdown.