Study Shows COVID-19 Changed To Spread More Efficiently Through Air
Aerosol shedding of the virus that causes COVID-19 occurs every time an infected person exhales.
The amount of virus shed is significantly greater in those infected with alpha, delta and omicron compared to ancestral strains and other variants that are not associated with increased transmissibility, a new study shows.
“This research showed that all three of those variants that have won the infection race,” Colorado State University public health engineer John Volckens told Nature magazine. “[They] come out of the body more efficiently when people talk or shout than the earliest strains of the coronavirus.”
The study, which was posted on the medRxiv preprint server on July 29 and has not yet been peer reviewed, tracked emerging variants to observe changes in how transmission occurs.
Using a device known as The Gesundheit-II, the team measured how much of the virus patients spread through exhaling.
“There’s a funnel where we have the participant put their face and head into, and we ask them to breathe, shout and sing into the cone,” co-author Kristen Coleman, a researcher who specializes in emerging infectious diseases at the University of Maryland School of Public Health, told the BBC. “On the other end of the cone is a sort of vacuum where it collects the aerosols coming out of the person’s mouth.
“We’re focusing on the smaller particles, the ones that float in the air and can be inhaled.”
Omicron, the variant that currently is dominant across the globe, stands apart for its virulence.
One omicron-infected participant in the study shed 10 million copies of the virus in 30 minutes — 1,000 times as much as the highest amount observed in participants with alpha or delta.
“This could mean that omicron has a higher propensity for super-shedding, which could not be predicted by its relatively low viral load in the nasal cavity,” Coleman tweeted. “Remember, when omicron first emerged and resulted in a huge super-spreader event at a dinner party? And then that kept happening?
“A combo of immune evasive properties and high viral aerosol shedding were likely responsible for omicron’s ascent and replacement of delta.”
The research shows that being outside still is safer than being indoors, but Coleman said omicron has changed that dynamic.
“The virus is actually evolving to be able to transmit more efficiently through air,” Coleman told Boston-based WHDH television station. “That’s why you’re seeing more instances where there are transmission events happening outdoors.”
To combat the spread of omicron and future variants, the study recommended a greater emphasis on non-pharmaceutical approaches.
“Interventions that disrupt airborne transmission are needed,” Coleman tweeted. “At this time, these include indoor air ventilation, filtration, air disinfection with germicidal UV [ultra-violet light] and high-quality masks.”
The researchers also conducted a study to measure the aerosol levels from participants wearing masks and not wearing masks.
“There’s a big difference there,” Coleman told the BBC. “The mask is definitely decreasing the amount of virus that is released into the environment.”
Although she acknowledged that some people have grown tired of wearing masks, Coleman said it is an important way to remain vigilant in the fight against COVID-19.
She also warned of future “variants with even higher viral aerosol shedding rates.”
“Evolutionary selection appears to have favored SARS-CoV-2 variants associated with higher viral aerosol shedding,” the study concluded. “Comparison with shedding rates for influenza suggests that continued evolution of still higher aerosol shedding rates may be possible.”