Journal retracts study on how far coronavirus can spread through droplets

A study suggesting fine droplets carrying the new coronavirus could linger in the air for at least 30 minutes and travel up to 15 feet has been retracted five days after its publication.

The research on so-called aerosol transmission, by a group of government researchers from the central Chinese province of Hunan, was based on a reconstruction of how the infectious disease Covid-19 spread on a bus on January 22 during the peak Lunar New Year travel season.

Hu Shixiong, the lead author of the study who works for the Hunan Provincial Center for Diseases Control and Prevention, said security camera footage demonstrated how the disease spread from an initial carrier of the virus to passengers as far as 15 feet apart without any interaction between them.

The findings, from a group of official researchers from the central province of Hunan, challenged the prevailing advice that people should remain apart at a safe distance of about six feet.

"It can be confirmed that in a closed environment with air-conditioning, the transmission distance of the new coronavirus will exceed the commonly recognized safe distance," the researchers wrote in a paper published in the journal Practical Preventive Medicine on March 5.

On March 10, the journal posted a "statement of retraction" signed by its editorial department, without offering any reasons.

The researchers also found that none of those passengers who wore face masks were infected, a finding that they said supported China's decision to ask people to wear a mask in public whether or not they show respiratory symptoms.

Before the retraction, a doctor in Beijing involved in the diagnosis and treatment of coronavirus patients told the South China Morning Post the study had left some questions unanswered.

For instance, the passengers sitting immediately next to the carriers were not infected, though they were most exposed to the disease-bearing droplets known as aerosols.

"Our knowledge about this virus's transmission is still limited," he said.

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