The COVID-19 infection rate in China is at a low level, suggesting success in the country's epidemic control measures, with Wuhan, Hubei province, as the main battlefield, the Chinese Center for Disease Control and Prevention said on Monday, citing a large-scale national epidemiological survey.

The survey covered more than 34,000 residents in Hubei province, including Wuhan, its capital, as well as six other provinces and municipalities such as Beijing and Shanghai, as well as Liaoning and Jiangsu provinces.

During the survey, organized by China CDC one month after the COVID-19 outbreak in Wuhan was contained earlier this year, the serum of its participants was tested for antibodies for the novel coronavirus, which causes COVID-19, to estimate the rate of infection among the population.

The novel coronavirus can stimulate the human body to produce specific antibodies after infecting humans, and the identification of such antibodies in a person's serum indicates that they were very likely to have been infected by the virus.

The survey showed that 4.43 percent of residents in Wuhan, the city hit hardest by the epidemic in China, tested positive for the antibodies, while the figure fell to only 0.44 percent in places in Hubei other than Wuhan.

In the other six provinces and municipalities, the figure was extremely low. Out of the more than 12,000 people that received the test in those areas, only two tested positive for novel coronavirus antibodies.

The survey showed that China has successfully contained the COVID-19 epidemic and effectively prevented the massive spread of the virus from Wuhan to other places, the center said.

Similar serum tests conducted in Spain from April 27 to May 11 found the average positive rate on a national level ranged from 3.7 percent to 6.2 percent. Tests in Switzerland starting from April 6 showed a result of 11 percent in their fifth week, according to the center.

Analyzing the results of the survey, researchers found that the positive rate is significantly higher in groups that had contact with confirmed COVID-19 patients, and middle-aged people and seniors were most likely to test positive for the antibodies, China CDC said.