How Respiratory Viruses Really Spread

We got it wrong with cholera, measles, tuberculosis, and SARS-CoV-2

Source: iStock/exdez

How an infectious disease spreads from one person to another is a question so vital that if we get it wrong, we will fail to control its spread and may even make it worse than it has to be.

During the 19th century in London, people believed that miasma (‘bad air’) spread cholera, a diarrheal bacterial disease. So, stinky sewers were dumped into the Thames River, a major source of drinking water. This move ended up killing far more people, as in fact cholera spreads via contaminated food and water.

We have made similar mistakes with measles and tuberculosis, which are aerosol infections that we thought, for decades, were spread by droplets. And most recently, we have done the same with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the culprit behind the Covid-19 pandemic.

Droplets vs. aerosols

In July 2020, the World Health Organization (WHO) stated that SARS-CoV-2 spread via respiratory droplets that people emit by sneezing and coughing to object surfaces or another person within <1 meter apart. The same went for the U.S. Centers for Disease Control and Prevention (CDC), which also did not acknowledge that SARS-CoV-2 can spread via…