Coronavirus: Modelling show COVID-19 could remain in air for 'several minutes' after cough, sneeze

The study involved more than 30 researchers.
The study involved more than 30 researchers. Photo credit: Aalto University

New research from Finland indicates that there is a risk that particles carrying coronavirus could remain in the air longer than previously thought after someone coughs, sneezes or speaks.

Scientists from four universities in the country studied how small airborne aerosol particles emitted from the respiratory tract when someone coughs or sneezes are transported in the air. 

Using an average supermarket layout as a test subject, the scientists used modelling to see what happened when a person coughs in an aisle between shelves, taking into consideration ventilation in the store. 

The study involved more than 30 researchers from Aalto University, VTT Technical Research Centre of Finland and the Finnish Meteorological Institute.

The modelling was carried out independently by three of the four institutes involved using the same starting conditions, with each model obtaining the same results.

According to the study, once someone coughs or sneezes, the particles spread out of the immediate vicinity of that person and it can take several minutes before they dilute.

"Someone infected by the coronavirus, can cough and walk away, but then leave behind extremely small aerosol particles carrying the coronavirus," said Aalto University Assistant Professor Ville Vuorinen.

"These particles could then end up in the respiratory tract of others in the vicinity."

The simulation also showed that the particles could travel as far as over two supermarket aisles.

While stressing they were preliminary results, Jussi Sane, chief specialist of the Finnish Institute for Health and Welfare said the study highlighted how there remained a lot about COVID-19 to be learned.

"Based on the modelling of the consortium, it is not yet possible to directly issue new recommendations. However, these results are an important part of the whole, and they should be compared with the data from real-life epidemic studies,’ Sane said.

According to the World Health Organization, COVID-19 is transmitted through "droplets generated when an infected person coughs, sneezes, or speaks", and is not airborne. 

"These droplets are too heavy to hang in the air. They quickly fall on floors or surfaces," the organisation states.

It's for this reason that people are urged to wash their hands often, for at least 20 seconds, and avoid touching their faces.

Experts' understanding of how COVID-19 spreads continues to evolve as more and more research about the virus is conducted.

Initially, it was thought the virus was only spread by people showing symptoms, however, the Centers for Disease Control and Prevention in the United States later warned that as many as 25 percent of people infected with COVID-19 may be asymptomatic. 

According to New Zealand's Ministry of Health, it is not common for COVID-19 to be spread by people before symptoms appear, but it can happen.

"To date, there have been no confirmed instances of a person with COVID-19, but who never developed symptoms, spreading the virus. It still may be possible for this type of spread to occur and good hygiene is key to preventing this."

As of Friday, there have been 1283 confirmed or probable cases of COVID-19 in New Zealand. Two people have died as a result of the virus.