When COVID-19 flared in the northern Chinese border region of Ejin late last year, it revealed a key impediment to the country charting an exit from its zero-tolerance pandemic strategy.

The health care system is so unprepared that any major shift away from "COVID zero" — which in China has meant frequent mass testing, swift quarantines, lockdowns and sealed international borders — risks a public health crisis.

In Ejin, home to about 30,000 in the Chinese province that borders Mongolia, several dozen infections in mid-October quickly overwhelmed the two local hospitals. Authorities had to transfer more than 140 patients by train to the provincial capital of Hohhot, over 1,000 kilometers away, according to local media.