Infectious particles can spread beyond 6 feet when someone with COVID-19 coughs without a mask, study suggests

• People with COVID-19 may spew infectious particles that can spread beyond 6 feet, a study suggests.
• Cambridge University scientists used computer simulations to test scenarios of a person coughing.

When a person with COVID-19 coughs without a mask, they could spew infectious particles that travel beyond 6 feet, according to Cambridge University scientists.

The scientists said in a press release Tuesday that, according to computer models, most larger droplets fall on nearby surfaces, but how far and quickly smaller droplets travel varied.

This means, in the absence of masks, a person with COVID-19 could infect another person at 6 feet, even when outdoors, the scientists said.

The study, published in science journal Physics of Fluids, tested ten scenarios of a person coughing without a mask using computer simulations.

Epaminondas Mastorakos, professor in applied thermodynamics at Cambridge University and study lead, said that fluctuations in particle speed, temperature, and humidity meant the number of particles someone gets at the 6 feet mark can be "very different each time."

"We strongly recommend that people keep wearing masks in indoor spaces such as offices, classrooms, and shops," he said.

The 6-foot rule, keeping 6 feet apart from someone else, has been widely used to try slow the spread of coronavirus. The Centers for Disease Control (CDC) said in May that catching COVID-19 via inhalation of infectious particles further than six feet can occur. Factors such as bad ventilation and exposure of more than 15 minutes can increase the risk of contracting COVID-19, it said.

Research from the Massachusetts Institute of Technology (MIT) from April found social distancing of 6 feet was "insufficient" to stop airborne transmission of coronavirus indoors, but its physics-based models assumed particles was always spread evenly throughout a room.

The Cambridge scientists said that vaccination, ventilation and masks – while not 100% effective – were "vital" to contain the virus.