Imagine you think there are mice in your house. You can see the evidence – mouse droppings; gnawed or damaged skirting boards; holes left in food packaging. You call a local pest control team who confirm that you have mice and advise you on what is needed to remove them. Neither of you have actually had to see a mouse to reach this conclusion.
The same kind of thinking can be applied to the transmission of coronavirus. We don’t need to see the virus to understand how it spreads. Recent studies from China show that patients infected with Covid-19 in clinical settings exhale large amounts of virus, which remain present in the air and can be sampled and detected.
Because of this, scientists can reasonably infer that the virus contaminates its surrounding environment. People nearby may inhale it, and as the virus floats through the air, spreading further in poorly ventilated environments, those who are further away could also become infected. Importantly, scientists haven’t yet demonstrated that someone walking through a cloud of exhaled virus would develop Covid-19 from that particular exposure, and research in this area is ongoing. But there is growing evidence that the virus which causes Covid can remain in the air, and therefore pose a risk to people in that airspace.
The evidence that Covid can spread via aerosol transmission takes one of two different forms. First, many scientists now think that aerosol transmission explained some early outbreaks, such as those in an air-conditioned restaurant in Guangzhou, China, and at a choir practice in the US, where the virus was exhaled by people and may have remained in the surrounding environment before infecting others who inhaled it.
Second, aerosol transmission partly explains why countries that were early adopters of policies which targeted this kind of transmission have been more successful at controlling the virus. For example, south-east Asian countries were far quicker to adopt face masks, which are shown to reduce the spread of aerosols, than many western countries including the UK. (…)
Source: Understanding ‘aerosol transmission’ could be key to controlling coronavirus | Coronavirus | The Guardian