The World Health Organization (WHO) has said people exposed to high levels of air pollution over long periods could face a higher risk of developing severe Covid-19 infections.

WHO officials told the BBC they were looking into Asia, Africa and Latin America to help authorities include the risk in their plan to fight the pandemic.

They said they were mapping cities that have had high levels of air pollution because it has been linked to respiratory diseases.

The connection between high air pollution and high coronavirus death rates has also been suggested by two recent studies.

One of them was by researchers at Harvard University who found that the death rates in the US rose in places where air pollution was high.

They have suggested that a small increase in fine particle pollution in the years before the pandemic may increase the Covid-19 death rate by around 15%.

Other experts have said more research needs to be done for further confirmation.

The WHO estimates that there are around seven million deaths each year due to air pollution.