The World Health Organization has acknowledged there is emerging evidence the coronavirus can be spread by tiny particles suspended in the air.
Airborne transmission could not be ruled out in crowded, closed or poorly ventilated settings, an official said.
An open letter from more than 200 scientists had accused the WHO of underestimating the possibility of airborne transmission.
- If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs) or call your GP - don't show up at a medical centre
The WHO had previously maintained that the virus was transmitted through droplets when people cough or sneeze - droplets that do not linger in the air, but fall onto surfaces, which was part of why handwashing was identified as a key prevention measure.
"We wanted them to acknowledge the evidence," Jose Jimenez, a chemist at the University of Colorado who signed the paper, told the Reuters news agency.
"This is definitely not an attack on the WHO. It's a scientific debate, but we felt we needed to go public because they were refusing to hear the evidence after many conversations with them," he said.
WHO officials have cautioned the evidence is preliminary and requires further assessment.
Benedetta Allegranzi, the WHO's technical lead for infection prevention and control, said that evidence emerging of airborne transmission of the coronavirus in "crowded, closed, poorly ventilated settings that have been described, cannot be ruled out".
The evidence would have to be thoroughly evaluated, but if confirmed could mean changes to prevention advice including more widespread use of masks and more rigorous distancing - especially in bars, restaurants, and on public transport.
Read more about the Covid-19 coronavirus:
- See all RNZ Covid-19 news
- Covid-19 symptoms: What they are and how they make you feel
- Touching your Face: Why do we do it and how to stop
- Scientific hand-washing advice to avoid infection
- Your Covid-19 questions answered - from health and employment to managing anxiety
- A timeline: How the coronavirus started, spread and stalled life in New Zealand
- Coronavirus: A glossary of terms