Virus spread through air at western Sydney church, analysis concludes7th April 2021
“And we think we’ve got pretty good evidence, based on our analysis, that this disease was transmitted from one person who was highly infectious across a distance perhaps up to 14 metres below where they were sitting.”
Dr Corbett said the unique shape of the church, the act of singing and the fact that the man was in his most infectious period – the days immediately before symptom onset – all contributed to the spread.
Over the past year, increasing evidence has shown the novel coronavirus can be transmitted through aerosol spread.
Although initial hypotheses were based on what scientists know about transmission of the influenza virus or other respiratory illnesses, instances of airborne spread of COVID-19 have been shown in research and practice.
Professor Michael Ward, a disease mapping expert at the University of Sydney, said it “certainly is plausible” for the virus to travel the distance seen in the church.
“Aerosols do slowly drop, so the fact that he was up in the choir loft also makes sense,” he said.
In his own research, Professor Ward has found aerosol spread of COVID-19 is easier in lower-humidity environments. In the case of the church outbreak, which occurred in the middle of a dry winter, closed doors and windows were probably also a factor, limiting ventilation, he said.
UNSW professor of respiratory medicine Guy Marks – whose research has shown the risk of COVID-19 transmission is higher when coughing, breathing heavily or yelling – said he also thought it was possible the outbreak could have occurred entirely through aerosol spread, as has been demonstrated in situations involving choirs and group singing abroad.
“Basically, talking is enough to generate [aerosol spread] and singing is just enhanced talking,” Professor Marks said.