China's worst coronavirus outbreak since the start of the pandemic a year and a half ago escalated Wednesday with dozens more cases around the country, the sealing-off of one city and the punishment of its local leaders.

Since that initial outbreak was tamed last year, China's people had lived virtually free of the virus, with extremely strict border controls and local distancing and quarantine measures stamping out scattered, small flareups when they occurred.

Now, the country is on high alert as an outbreak of cases connected to the international airport in the eastern city of Nanjing touched at least 17 provinces. China reported 71 new cases of COVID-19 from local transmission Wednesday, more than half of them in coastal Jiangsu province, of which Nanjing is the capital.