Western Sydney team investigate airborne COVID spread in world-leading research

The team at Western Sydney Local Health District’s (WSLHD) Public Health Unit have found evidence that airborne transmission of COVID-19 can happen under the right conditions following an investigation into an outbreak at a western Sydney church.

The outbreak stemmed from several July 2020 church services where 12 people who attended the services in western Sydney were infected with COVID-19.

Dr Anthea Katelaris is a Public Health Doctor at the WSLHD Public Health Unit and the lead author of the research paper published in the Centers for Disease Control Emerging Infectious Disease journal this week.

While the vast majority of COVID-19 transmission occurs from direct or close contact between people, this study supports previous studies which suggest that, occasionally, airborne transmission of COVID can occur under certain conditions,” said Dr Katelaris.

The initial person infected was a choir singer who was asymptomatic – they were not showing any symptoms of COVID-19 when they sung at the church service. 

They were located in a choir loft, 3.5 metres above the congregation, which they entered before and left after the service. They did not touch objects or mix with the general congregation, making direct transmission unlikely.

This was backed up by video recordings of the service, which the team – along with doctors from The Westmead Institute for Medical Research and the University of Sydney – meticulously reviewed.

Schematic diagram of church layout showing seating locations of primary and secondary case-patients during an outbreak of infection with severe acute respiratory syndrome coronavirus 2, Australia, 2020. 

As people who contracted COVID were interviewed, the clues were pieced together by the team at our Public Health Unit, the theory that COVID had spread in the air began to become clear.

Genome sequence performed by the team at Institute of Clinical Pathology & Medical Research (ICPMR) revealed all cases were genomically similar and backed up this theory.

Measurements taken in the building found COVID could have spread up to 15 metres in the church.

“The conditions that lend themselves to airborne spread of COVID seem to be in crowded indoor settings with poor ventilation, especially when combined with higher-risk activities like singing or shouting,” said Dr Katelaris.

“This is why we recommend physical distancing – especially during activities like singing – wearing a mask when people cannot physically distance, gathering outdoors where possible, and increasing natural or mechanical ventilation.”

Dr Anthea Katelaris, Public Health Doctor, speaking to the media on the team’s research.

Dr Katelaris thanked churchgoers for following recent health advice and adhering to restrictions when needed, as well as the western Sydney church and its congregation for their cooperation in the world-leading study.

“In this cluster investigation in particular, we were very grateful that the church community was very cooperative and resourceful, for example, by streaming their services online.”

The study highlights the importance of optimising ventilation in all indoor settings – something that’s especially important coming into winter months.

Most importantly, if you have COVID-19 symptoms, get tested!