Covid-19 virus evolving to become more airborne?
Covid-19 virus evolving to become more airborne? That appears to be so, according to new scientific studies.The virus now appears to spread through the air, though the good news is that masks reduce the amount of infectious virus.
About 85 percent of coronavirus RNA detected in COVID-19 patients’ breath was found in fine aerosol particles less than five micrometers in size, researchers in Singapore report August 6 in Clinical Infectious Diseases.
The finding is bad news as it suggests that COVID-19 is spreading mainly through the air in fine droplets that may stay suspended in air for hours rather than in larger droplets that quickly fall to the ground and contaminate surfaces.
However, this seems to vary from variant to variant in a manner which seem to indicate that the virus is evolving with each new variant coming out. Donald Milton and colleagues at the University of Maryland in College Park found that people who carried the alpha variant had 18 times as much viral RNA in aerosols than people who carried with less-contagious original virus. The research also found that loose-fitting masks could cut the amount of virus-carrying aerosols by nearly 50%.
The debate over whether coronavirus is an airbourne virus or not has been going on since the beginning of the COVID-19 pandemic. In July last year, about 200 scientists wrote a letter to the World Health Organization asking for the organization to acknowledge the aerosol spread of the virus. In response to that, in April this year, WHO upgraded its information on transmission to include aerosols a few weeks after the U.S. Centers for Disease Control and Prevention had acknowledged aerosols as the most likely source of spread. But some experts argue that there is still no direct evidence that the virus spreads mainly through the air.
“There’s lots of indirect evidence that the airborne route — breathing it in — is dominant,” says Linsey Marr, a civil and environmental engineer at Virginia Tech in Blacksburg, who studies viruses in the air. Linsey is one of the 200 scientists who wrote to the WHO last year.
Classifying the virus as airbourne means that health care workers would now be required to take more costly and resource-intensive measures to stop the spread of the disease. This is likely one of the reasons, infection control experts have been reluctant to label the coronavirus airborne without strong proof.
To prove the aerosol route, mechanical engineer Kwok Wai Tham of the National University of Singapore performed an experiment to measure how much virus COVID-19 patients produce when they breathe, talk or sing. With his colleagues, he set up a mobile lab in Covid-19 patients’ rooms and called for volunteers to stick their heads into a large metal cone. With the metal cone, researchers collected both aerosols and larger droplets that the patients exhaled while breathing quietly for 30 minutes, while repeating passages from Dr. Seuss’ Green Eggs and Ham for 15 minutes, or while singing simple tunes like the “Happy Birthday” song, “Twinkle, Twinkle Little Star” or the “ABCs” for 15 minutes.
They then tested both the aerosols and the large droplets in the air samples for coronavirus RNA. From the results, they calculated how many copies of the virus’s nucleocapsid protein gene, or N gene, were present in the air samples.
Of the 22 patients who sang for humanity, only 13 produced detectable levels of viral RNA in aerosols. This means that singing created the most virus-laden aerosols. However, some people generated more while talking. Another thing learnt from the experiment is that the overall amount of virus that people produced varied widely from person to person.
Some people are more likely to spread the virus than others. In this experiment, the differences weren’t due to symptoms as some asymptomatic people produced more virus than those with fevers, coughs or runny noses. One factor stood out though, recently infected people tended to produce more virus. This agrees with previously known studies that highlighted the fact that people are most contagious in the first week after catching the coronavirus.
Skeptics where quick to point out that viral RNA could be debris from dead viruses that can’t cause infection. One such skeptic is Andrew Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health.
He went on, “In the absence of infectious virus, the significance of aerosols on transmission is still a bit unclear.”
“It would be difficult to make the case that this was what is responsible for increased spread of alpha”, he said.
However other studies performed recently produced data that suggests that the coronavirus might be evolving toward more efficient spread through the air.