Given that coronavirus is a new disease, scientists have been rapidly researching how it is transmitted and how best to prevent infection.
The World Health Organization (WHO) has so far said that the virus is transmitted via droplets that are released when people cough or sneeze, but new evidence has now emerged that suggests airborne transmission has been underestimated.
Can coronavirus be transmitted in the air?
An open letter from more than 200 scientists, which was published in the journal, Clinical Infectious Diseases on Monday (6 July), has accused the WHO of underestimating the possibility that coronavirus can be spread by tiny particles in the air.
Scientists have suggested that airborne transmission cannot be ruled out in crowded, closed or poorly ventilated settings.
The WHO has previously insisted that coronavirus is only transmitted via droplets that are emitted from coughs or sneezes. Such droplets do not linger in the air, but rather fall onto surfaces, and as such, handwashing has been identified as a key preventative measure.
However, 239 scientists from 32 countries have disagreed with such claims, saying there is strong evidence that suggests the virus can also be spread in the air.
It has been claimed that it could be transmitted through much smaller particles released when people talk and breathe out float around in the air for several hours after.
What did the WHO say?
In response to the claims, the WHO updated its guidance on the transmission of coronavirus on Thursday (9 July), acknowledging the possibility of airborne transmission.
The WHO admitted that there was scientific evidence to suggest that airborne transmission was possible in certain settings, such as enclosed and crowded spaces, but cautioned that such 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".
Commenting on the WHO’s response, Jose Jimenez, a chemist at the University of Colorado who signed the letter, told Reuters: “This is a move in the right direction, albeit a small one.
“It is becoming clear that the pandemic is driven by super-spreading events, and that the best explanation for many of those events is aerosol transmission.”
What does it mean for current rules?
Following its review of scientific evidence, the WHO said that coronavirus spreads through contact with contaminated surfaces, or by close contact with people infected with the virus.
It said transmission occurs through saliva or respiratory droplets that are released when an infected person coughs, sneezes, speaks or sings.
As such, guidance states that people should avoid crowds, ensure good ventilation in buildings, observe social distancing, and make use of masks when physical distancing is not possible.
If evidence of airborne transmission is confirmed, the current guidance on preventing the spread of the virus may be forced to change.
In this case, it could result in more widespread use of masks and more stringent rules on social distancing, particularly in higher-risk areas, such as public transport, pubs, bars and restaurants.