The aim of social distancing is to limit the transmission of the virus and most countries around the world recommend some distancing between members of different households of between 1-2 metres. The 2m rule comes from research in the 1930s when scientists established that droplets of liquid released by coughs or sneezes will either evaporate quickly in the air or be dragged by gravity down to the ground. They estimated that for viruses in general, the majority of those droplets would
land within 1-2 metres. But some researchers are now concerned that SARS COV-2 is not just carried in droplets but that it can also be transported through the air in tiny particles called aerosols. If that is the case, then the flow of wind from someone's breath could carry the virus over longer distances.
Guidance for social distancing around the world varies. Until 4th July the UK guidance was to stay at least 2 metres, but from the 4th July the rule was changed to 1m plus, which means although you should ideally stay 2m apart, if that's not possible then it should be 1m and with other measures if possible (face coverings and not sitting face to face).
At the end of June the WHO’s recommendation of 1m was recommended by China, Denmark, France, Hong Kong and Singapore, and people can either choose to, or are required to, wear face masks in public spaces, with some countries fining for non compliance. Meanwhile, Australia, Belgium, Greece, Germany, Italy, Spain, and Portugal are recommending 1.5m of physical distance, while the US and South Korea have opted for specific distances of 1.8m and 1.4m, respectively.
However, it doesn't look like the difference in social distancing measures has made a difference in the infection rate on its own, earlier lockdown or better track and trace programmes seem to make a bigger difference.
Distance and the amount of time you are with an infected person is important with a leading scientist in the UK saying that "Spending two seconds one metre apart is as dangerous as spending one minute two metres apart". People get infected when they are exposed to a certain number of viral particles. If the other person coughs or sneezes, the viral threshold can be reached quite quickly. However, even talking releases some virus particles into the air. The longer you spend with an infected person, especially in an enclosed space, the likelier it is you’ll become infected. Travelling via droplets, the virus is likely to spread further through activities such as shouting or singing and there are numerous instances where multiple choir members have come down with coronavirus.
Where you are also makes a difference. Scientists say that the infection seems to be more easily spread indoors than outdoors and things like air quality, humidity, weather and air conditioning may also have an impact on transmission.
A study by Japan’s National Institute of Infectious Diseases found that the chances of transmitting the virus were 19 times higher indoors than outside after looking at 110 cases of COVID-19 and tracing the contacts of those infected.