Unmasked jogger ‘infected 39 with Omicron’ in park

Study finds dozens of cases traced back to man who ran for half an hour in Chongqing in August

An unmasked jogger is thought to have infected 39 people with Covid-19 in the space of half an hour at a park in Chongqing, according to a study by health authorities.

The 41-year-old man was the first known case of the Omicron subvariant BA.2.76 identified in the city and had fatigue but no other symptoms when he went for a run at about 7am on August 16.

Only one of those he infected had been wearing a mask.

The jogger spent about half an hour in the park, running four times round a lake on a fourmetre-wide jogging track. He did not talk to anyone, touch anything or use the toilet.

The temperature was over 33 degrees Celsius, with mild humidity and local wind speeds between 0.5 and three metres per second.

When the man reached home, he received a call from local health authorities and was told a PCR test he had taken the previous day was positive.

The study, written by researchers from the Chinese Centre for Disease Control and Prevention in Beijing and Chongqing and published in the CDC’s weekly journal, said the patient had passed the virus to a total of 48 people, including his wife, four colleagues, two foot massage therapists and a breakfast server.

But most transmissions took place in the park. Security camera footage showed over 100 unmasked people had come within a metre of the jogger. They were regarded as close contacts and sent to quarantine.

Thousands who did not have any direct encounter with the jogger were rated “at risk” and told to stay at home for three days.

Among the park visitors, 13 close contacts and 20 at-risk individuals produced positive test results. Further epidemiological investigations found no other exposure history in these people, and they did not know one another. Genetic sequencing suggested they were infected by the same strain from patient zero.

Those infected also included six park employees, only one of whom was wearing a mask and was thought to have been given a secondary infection after coming into contact with two colleagues.

The researchers said they believed the jogger had been infected on a flight between Hohhot in Inner Mongolia and Chongqing on August 13.

A day earlier, the plane carried four infected passengers from Tibet on a flight from Chongqing to Hohhot. The cabin was not disinfected overnight and the man sat in a seat close to where those passengers were sitting. He was the only secondary infection reported on the flight, where wearing a mask was compulsory.

It was generally believed the coronavirus spread less easily outdoors, the researchers led by Zhang Lijie wrote. Some studies had reported outbreaks in an open environment, but “these reports do not exclude the possibility of direct contact with cases in indoor spaces”, they said.

But they wrote the “only possible exposure” for many of those infected was they were in the park at the same time as the jogger.

The study said heavy breathing might have helped spread the virus, adding: “Patient zero jogged for 35 minutes, it is reasonable to assume that he may have emitted an abundance of virus-laden respiratory particles and spread Sars-CoV-2.”