coronavirus is now airborne, according to the US Centers for Disease Control and Prevention (CDC).

There is evidence that under certain conditions, people with Covid-19 could infect those who are more than six feet away, CDC says in its updated guidelines.

The conditions listed include "enclosed spaces that had inadequate ventilation" and when an infected person is "breathing heavily, for example while singing or exercising".

The American health body says some infections can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours.

It likened this update to how infections like tuberculosis, measles, and chicken pox spread.

This update states that reports show that those with Covid-19 infected others shortly after leaving an area.

"Under these circumstances, scientists believe that the amount of infectious smaller droplet and particles produced by the people with Covid-19 became concentrated enough to spread the virus to other people," the CDC statement read in part.

The World Health Organization says the main way the virus spreads is through close contact with virus-containing droplets - large and small - that are emitted when someone coughs, sneezes, sings, talks or breathes.

When people are in proximity, within six feet, they are exposed to the whole spectrum of spray that can cause infection, WHO says.

To avoid further spread of Covid-19, people have been advised to wear masks when in public settings, observe social distancing of at least two metes apart and sanitise.