Obesity, age, and COVID-19 infection can make someone a SARS-CoV-2 super-spreader

Scientists and public health experts have long known that some people, known as “super-spreaders”, can transmit COVID-19 with incredible efficiency and devastating consequences.

Now researchers at Tulane University, Harvard University, MIT and Massachusetts General Hospital have learned that obesity, age, and COVID-19 infection are correlated with a propensity to breathe out no more respiratory droplets – the main spreaders of SARS-CoV-2, the virus that causes COVID-19. Their results were published in Proceedings of the National Academy of Sciences.

Using data from an observational study of 194 healthy people and an experimental study in non-human primates with COVID-19, the researchers found that exhaled aerosol particles vary widely from subject to subject. the other. Those who were older with a higher body mass index (BMI) and increasing degree of COVID-19 infection had three times as many exhaled respiratory droplets than others in the study groups.

The researchers found that 18% of human subjects accounted for 80% of the exhaled particles in the group, reflecting a distribution of exhaled aerosol particles that follows the 20/80 rule seen in other infectious disease outbreaks – meaning that 20% of infected people are responsible for 80% of transmissions.

Aerosol droplets in non-human primates increased as the infection with COVID-19 progressed, peaking at one week after infection before returning to normal after two weeks. Notably, as the infection with COVID-19 progressed, the viral particles became smaller, reaching the size of a micron at the peak of the infection. Tiny particles are more likely to be expelled when people breathe, speak, or cough. They can also stay afloat for much longer, travel farther in the air, and penetrate deeper into the lungs when inhaled.

The increase in expired aerosols has occurred even in people with asymptomatic cases of COVID-19, said Chad Roy, PhD, corresponding author and director of the aerobiology of infectious diseases at the National Primate Research Center of Tulane.

We have seen a similar increase in droplets during the acute infection phase with other infectious diseases like tuberculosis. It seems likely that viral and bacterial respiratory tract infections can weaken the mucus in the respiratory tract, which promotes the movement of infectious particles in this environment. “

Chad Roy, PhD, Director, Infectious Disease Aerobiology, Tulane National Primate Research Center

The generation of respiratory drops in the airways varies among people based on their body composition, said lead author David Edwards, PhD, professor of biomedical engineering practice at Harvard University.

“While our results show that young and healthy people tend to generate significantly fewer droplets than older, less healthy ones, they also show that each of us, when infected with COVID-19 , may run the risk of producing a large number of respiratory droplets. Edwards said.