The Blood Center of Shandong Province, the second most populous in China, issued red alert warnings for insufficient inventory for two blood types in recent days, China National Radio reported.

Fewer people were on the streets due to the Covid situation and the cold weather, while early holiday at universities also reduced the pool of student donors, the state-owned media said, citing officials.

Red alert is the highest level of warning, which means the blood in store can only meet the dosage of acute and critically ill patients for three days, according to the report.

The Health Commission of Suzhou city in the eastern province of Anhui called for voluntary blood donation in a Dec 20 statement on its official website. The Covid pandemic posted an “enormous challenge” to blood collection, resulting in tightness of supply in medical treatment, the statement said.

China is experiencing a wave of infections after it rapidly relaxed most pandemic controls since last month.

Covid cases have surged in major cities including Beijing and Shanghai, where patients are flocking into hospitals and unprepared residents are scrambling for medicines.

Growing stress on the nation’s health system adds to the fear that the reopening might lead to more severe cases and deaths, although not all fatalities are captured in official reports.

Earlier this month, China revised guidelines allowing people who developed Covid with no critical symptoms to donate blood seven days after they test negative through a nuclear acid test or antigen test.

The previous rule had barred even those in close contact with Covid patients from giving blood.