New York, Jun 9 (IANS): Speaking without masks in confined spaces poses the greatest risk of spreading SARS-CoV-2, the virus that causes Covid-19, to others, according to a study.

The study published in the Journal of Internal Medicine describes how different sized respiratory droplets emitted while speaking span a continuum of sizes and can carry different amounts of virus.

Most concerning are intermediate-sized droplets that remain suspended in the air for minutes and can be transported over considerable distances by convective air currents.

"We've all seen some spit droplets flying when people talk but there are thousands more, too small to be seen by the naked eye," said Adriaan Bax, from the US National Institute of Diabetes and Digestive and Kidney Diseases in Maryland.

"When the water evaporates from such speech-generated, potentially virus-rich droplets, they float in the air for minutes, like smoke, thus putting others at risk," Bax added.

Since the beginning of the Covid-19 pandemic last year, researchers have argued that Covid-19 was not airborne. However, US Centers for Disease Control and Prevention (CDC), in May, announced that exposure to respiratory fluids -- very fine respiratory droplets and aerosol particles -- present in the air and which carry viruses are the main reason for contracting Covid-19 infection.

The Indian government also in an advisory stated that aerosol and droplets are key modes of transmission of the virus. It added that the aerosol can travel up to ten metres from the infected person and that aerosol through the infected person can fall within two metres but can be carried to ten metres through the air.

The advisory said, to prevent it people should continue wearing masks, wear double masks or an N95 mask. The introduction of cross ventilation and exhaust fans will be beneficial in curtailing the spread of the disease, it said.