Residents line up to take nucleic acid tests in Zhengzhou, Central China's Henan Province on January 4, 2022. Photo: VCG

Mahjong rooms, funerals and family gatherings were found to be the three transmission chains of the latest COVID-19 outbreak in Zhengzhou, capital of Central China's Henan Province, which was put in partial lockdown overnight after two asymptomatic cases were detected in the city on Monday, the local authorities announced on Tuesday. 

A total of 161 close contacts and 335 secondary contacts were detected during the flareup. The two positive cases were confirmed to be mild and under stable condition, local health officials said at Tuesday's press conference. 

As of Tuesday evening, the city reported two confirmed cases and nine asymptomatic carriers. 

Nucleic acid testing to key groups in four major areas of the city has been conducted as of Tuesday and no positive cases were found among 349,800 samples, officials said. 

So far, four subway stations in Zhengzhou were shut down on Tuesday due to the latest spike. In key areas, shopping malls, supermarkets and produce stores have restrictions on the number of shoppers while schools were closed. 

Yuzhou, another city in Henan Province, has established 10 quarantine sites with 1,500 rooms and is expected to expand the number to 5,000 by Wednesday noon as the city detected 20 infections, including two confirmed cases and 18 asymptomatic cases as of Tuesday noon. 

The city, with a population of about 1.2 million, required local residents to stay at home from Monday night after it reported three asymptomatic cases of COVID-19 in the past two days. It has also shut down bus and taxi services and closed shopping malls, museums and tourist attractions.