The study used a sample of 34,000 people in the general population in Wuhan — the original epicenter of the pandemic — and other cities in Hubei province, as well as Beijing, Shanghai, and the provinces of Guangdong, Jiangsu, Sichuan and Liaoning to estimate Covid-19 infection rates.
The study aimed to estimate the scale of past infections in a population by testing blood serum samples from a pool of people for coronavirus antibodies. Its findings are not taken to be final statistics of how many people in a given area have been exposed to the virus.
The Chinese CDC said the study was conducted a month after China “contained the first wave of the Covid-19 epidemic.” The prevalence rate outside of Wuhan is significantly lower, the study showed. In other cities in Hubei, only 0.44% of residents surveyed were found to have coronavirus antibodies.
Outside the province, antibodies were only detected in two people among the more than 12,000 residents surveyed.
Underreported coronavirus infections
Yanzhong Huang, a senior fellow for global health at the Council on Foreign Relations, said the study points to a problem of underreporting in infections during the height of the outbreak in Wuhan, partly due to the chaos at the time and a failure to include asymptomatic cases in the official count of confirmed cases.
Underreporting is a problem faced by health authorities in many countries, often due to a lack of capacity and resources. Antibody studies conducted by researchers in other parts of the world also show the coronavirus was much more prevalent than official numbers suggest.
But in China, there is also the question of transparency, as officials gave the public more optimistic data than they had access to internally.
Effective containment in Wuhan
The study highlights a huge contrast between the coronavirus antibody prevalence rates inside and outside of Wuhan.
Huang said the significantly lower rates in other Chinese cities suggest “Chinese containment efforts were indeed speedy and effective, especially compared to cities like New York.”
In an unprecedented bid to contain the rapidly spreading virus, Wuhan was sealed off from the outside world on January 23, with all flights, trains and buses canceled, and highway entrances blocked.
Nevertheless, the sweeping measures have been heralded by the Chinese government as having allowed the country to turn a corner in its fight against the outbreak.
The Chinese CDC, meanwhile, also highlighted China’s victory in containing the virus when releasing the antibody study results on Monday.
“The results of the study show that our country’s population has a low infection rate. It indicates that China has succeeded in controlling the epidemic with Wuhan as the main battlefield, and effectively controlled the large-scale spread of the epidemic,” the agency said.
CNN’s Nick Paton Walsh contributed to this story.