Nigeria’s petroleum regulator has ordered oil and gas companies to reduce their offshore workforce and move to 28-day staff rotations as part of measures to curb the spread of the coronavirus, according to a circular seen by Reuters.

Health experts fear a widespread outbreak in Africa’s most populous country, which has about 200 million inhabitants, and the country is keen to protect oil production, which provides90% of much-needed foreign exchange.

A coronavirus case on an offshore rig could spread quickly among workers and have a potentially devastating impact on production.

Director of the Department of Petroleum Resources Sarki Auwalu says only staff on essential duties will be allowed to travel to offshore or remote locations.

“Non-essential staff currently at offshore/remote locations should be withdrawn with immediate effect,” he says in a statement.

Nigeria, which has 97 confirmed coronavirus cases, has shut international airports, closed all land borders and imposed curbs on cargo vessels allowed to dock at its ports in an effort to contain the outbreak.

Rivers State, in which Port Harcourt serves as the hub of Nigeria’s oil industry, closed its own borders to human traffic this week.

Oil and gas companies operating in Nigeria have previously said that the health and safety of workers was their top priority.

Industry sources said that a number of oil companies had already shifted from 14-day rotations to 28 days. Some are also implementing a 14-day quarantine for workers before they leave for rigs. Oil prices have fallen by two thirds since the start of the year, which has forced Nigeria to cut its budget and prompted oil companies to reduce their spending plans.