Wuhan’s cases may have been 10 times higher, shows study

BEIJING/WUHAN: The scale of the Covid-19 outbreak in Wuhan early this year may have been nearly 10 times the recorded tally, a study conducted by China’s public health authorities has indicated.

About 4.4% of those tested were found to have specific antibodies that can fight off the pathogen that causes Covid-19, indicating they were infected some time in the past, according to a serological survey of more than 34,000 people conducted in April by the Chinese Center for Disease Control and Prevention (CDC). The data was released late on Monday.

That ratio would suggest that with Wuhan home to about 11 million people, as many as 500,000 residents may have been infected, nearly 10 times more than the 50,000 confirmed Covid-19 cases reported by health authorities in mid-April, when the survey was conducted.

Serological surveillance has been widely used by health professionals around the world to gauge the true scale of epidemics, from Covid-19 to AIDS and hepatitis. The prevalence of disease derived from such studies can guide mitigation and vaccination efforts.

The survey showed a far less impact of the outside Wuhan, which was shut off as a way of containing the outbreak. The positive rate for antibodies dropped to 0.44% for Hubei province, which was also placed under a three-month lockdown. Only two people tested positive for the antibody among 12,000 surveyed in six other Chinese cities and provinces.