“Our results suggest that the timing of exposure relative to primary-case symptoms is important for transmission, and this understanding provides further evidence that rapid testing and quarantine after someone is feeling sick is a critical step to control the epidemic,” Martinez said.

“Our study is the largest to date to assess the health outcomes of hospitalised COVID-19 survivors after 12 months of becoming ill,” said Professor Bin Cao, from China-Japan Friendship Hospital.

“While most had made a good recovery, health problems persisted in some patients, especially those who had been critically ill during their hospital stay,” Cao said.