A sample collection medical worker in Mudanjiang takes off her protective clothing after becoming soaked in sweat due to the hot weather on Monday. Photo: Courtesy of medical staff in Mudanjiang

Mudanjiang, Northeast China's Heilongjiang Province, is conducting free nucleic acid tests on all its residents to identify COVID-19 infections and get a thorough understanding of the number of asymptomatic carriers, the second city in China to do so after Wuhan, Central China's Hubei Province.

Since Monday, residents waiting in long lines for tests have become the most common scene in Mudanjiang, home to about 2.8 million people. 

Some communities reached by the Global Times said the citywide COVID-19 tests will ensure every resident gets tested, except children under the age of 6 and invalids, as well as those who were tested during the past 14 days. 

The tests must be conducted before Saturday, several communities reached by the Global Times said on Wednesday, but many communities said they may finish before that date. The Mudanjiang city government and health authority could not be reached to confirm this information.

To complete this task, 1,196 medical staff and workers were dispatched from 23 medical institutions, the Mudanjiang Health Commission said. 

To ensure the collection of all test samples by Saturday, the city has assigned medical staff to different communities according to the amount of work required, a medical worker surnamed Zhang told the Global Times.

Testing for 500 households in a residential community in Xi'an district started on Tuesday morning, and the process was expected to be completed around Wednesday afternoon, a staff member from the community surnamed Wang told the Global Times on Wednesday.

Local residents have been very cooperative, with many starting to line up from 6:30 am, half an hour before the testing began, another residential community worker told the Global Times on condition of anonymity. 

Residents had to register beforehand by providing their ID information and specifying their employers. 

Mudanjiang residents can check their test results via their smartphones by entering their personal ID information and names at any time.

Mudanjiang is the second city in China to conduct citywide COVID-19 tests after Wuhan, which tested 9.89 million residents within 10 days. 

In Wuhan, 300 asymptomatic patients were found after 9,899,828 residents were tested, with no confirmed COVID-19 cases. The testing cost 900 million yuan ($126 million), which will be shouldered by the Wuhan government.

Asked whether China should conduct nationwide tests after the campaign in Wuhan proved to be a success and eased the public's concerns over the spread of the virus amid the resumption of work, Wang Peiyu, a deputy head of Peking University's School of Public Health, told the Global Times that nationwide testing is not necessary.

Expanding nucleic acid tests among close contacts of confirmed cases or asymptomatic virus carriers and key posts that are at risk of exposure to the novel coronavirus will be sufficient. Nationwide testing for everyone would be inefficient and a waste of money and human resources, Wang said.

Most regions in China have been cleared of COVID-19 infections and resumed work and schooling, but cases of COVID-19 have been repeatedly reported in Mudanjiang in recent days. 

As of Tuesday, there were 15 asymptomatic patients in Heilongjiang, all of whom were in Mudanjiang, the provincial health commission reported on Wednesday.