Seattle: Six months into a pandemic that has killed more than half a million people, more than 200 scientists from around the world are challenging the official view of how the coronavirus spreads.

The World Health Organisation and the US Centres for Disease Control and Prevention maintain that you have to worry about only two types of transmission: inhaling respiratory droplets from an infected person in your immediate vicinity or - less common - touching a contaminated surface and then your eyes, nose or mouth.

But other experts contend that the guidance ignores growing evidence that a third pathway also plays a significant role in contagion.

They say multiple studies demonstrate that particles known as aerosols - microscopic versions of standard respiratory droplets - can hang in the air for long periods and float more than four metres, making poorly ventilated rooms, buses and other confined spaces dangerous, even when people stay 1.5 metres from one another.

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