Asymptomatic patients and imported infections have become China’s chief concern.

Mainland China’s new coronavirus cases doubled in 24 hours as the number of infected overseas travellers surged, and new asymptomatic infections more than quadrupled.

Use of hydroxychloroquine has soared as the United States has quickly become the epicentre of the pandemic, though doctors prescribing it have no idea whether it works.

U.S. fatalities from COVID-19, the respiratory disease caused by the virus, hit 10,902 on Monday, rapidly closing in on Italy and Spain, the countries with the greatest loss of life to date, according to a Reuters tally of official data.

IATA said about $35 billion of tickets were due for refund at the end of the second quarter, and vouchers or a delayed refund was all airlines could offer. IATA has approached governments to ask them not to force airlines to provide cash refunds.

Airline passengers throughout the U.S. are increasingly taking to social media to air their frustration at not being able to get refunds for trips canceled amid the coronavirus pandemic. The U.S. Department of Transportation on Friday reminded carriers that they are required to reimburse fliers for fares and fees.

Hubs like Singapore, Abu Dhabi and Shanghai have halted most crew transfers, while global lockdowns have complicated travel from the Philippines, which supplies about a quarter of the world’s seafarers.

At risk is the flow of goods like food, medicine and energy via commercial shipping, which accounts for about 80% of global trade. While unseen by most consumers, restrictions on crews are among the unprecedented challenges wrought by the virus, which has ground major economies to a halt.