Is the Coronavirus Getting Better at Airborne Transmission?

Newer variants of coronavirus such as Alpha and Delta are highly contagious and infect more people than the original virus. Two new studies offer a possible explanation: Viruses evolved to spread more efficiently through the air.

The perception that the coronavirus is transmitted indoors has changed last year’s efforts to contain the pandemic, sparking heated debate over masks, social distancing and ventilation in public spaces.

Most researchers now agree that the coronavirus is transmitted by large droplets that quickly sink to the ground and much smaller droplets called aerosols. Aerosols float long distances indoors and allow viruses to settle directly in the lungs where they are most dangerous.

New research does not radically change this view. However, the results show that better masks are needed in some situations, which suggests that the virus is turning out to be more frightening.

“This is not an Armageddon scenario,” said Vincent Munster, a virologist at the National Institute of Infectious Diseases who led one of the new studies. “It’s like a modification to infect the virus more effectively. We all expected this and we can see that it is happening in real time now. ”

dr. Munster has shown that small aerosols travel much greater distances than large droplets, and the alpha variant is much more likely to cause new infections by spreading aerosols. The second study found that people infected with alpha emit about 43 times more virus in smaller aerosols than people infected with the older variant.

The study compared the alpha variant with the original virus or other older variants. These results may also explain why the delta variant is highly contagious and has replaced all other versions of the virus.

Lincy Marr, an airborne virus expert at Virginia Tech who was not involved in any research, said, “In the case of Delta, I wouldn’t be surprised if the odds were even higher.

Excessive options transparency can be caused by a variety of factors. Infection may require a lower mutant dose, more mutant virus aerosolizing, mutants may replicate more rapidly, or all three may be present.

The alpha variant has been shown to be twice as infectious as the original virus, and the delta variant has mutations that further increase its infectivity. As the virus continues to change, new variants can become more infectious, experts say.

But all the tools we have are still working fine to stop the spread. Even loose towels and surgical masks block about half of the fine aerosols that contain the virus, according to a study of people infected with the variant published in the Journal of Clinical Infectious Diseases this month.

However, in at least some crowded areas, people might consider switching to protective masks, said Don Milton, an aerosol expert at the University of Maryland who led the research. ..

“Aerosol production seems to be doing better, so we need better containment and better personal protection,” said Dr. Milton on viruses. “We recommend switching to a thicker mask.”

To compare the distribution of the different variants in the air, his team alphabetically cited participants with mild or asymptomatic infections or shouting “Happy Birthday”. I asked him to sing or shout the University of Maryland slogan, Go Terps.

People infected with the alpha mutant had more people infected with the original virus and had large amounts of the virus in their noses and throats. But even after correcting for the differences, people infected with the subspecies shed about 18 times more virus in the smallest aerosols.

However, the researchers only looked at four people infected with alpha and 45 people infected with the older mutant. Seama Rakdawara, a respiratory virologist at the University of Pittsburgh who wasn’t involved in any of the new studies, said it might distort the difference between the options.

An infected person cannot infect many other people or cannot be infected with the virus at all. The amount of virus released can depend on where it replicates in the airways, the lining of the environment, and other microorganisms that can transmit it.

Status of vaccination requirements in the US
Vaccination regulations. On August 23, the FDA granted full approval of Pfizer BioNTech’s coronavirus vaccine to people over the age of 16, paving the way for mandatory use in the public and private sectors. .. Such obligations are legally permitted and enforced by the courts.
University. More than 400 universities require their students to be vaccinated against Covid-19. Nearly all of them were in the states that elected President Biden.
School. California was the first state to require all teachers to be vaccinated and has announced it will include the Covid-19 vaccine as a prerequisite for school attendance in early fall. In Los Angeles, students over the age of 12 who attend live classes starting November 21 must be vaccinated. Vaccination requirements have been introduced for teachers and staff in New York, but are not yet in effect due to legal issues. On September 27, the Federal Court of Appeals overturned the decision to suspend its mission.
Hospitals and Medical Centers: Many hospitals and large healthcare systems require employees to be vaccinated. The commitment of health workers in California and New York appears to have forced thousands of inmates to be vaccinated.
New York: Indoor restaurants, gyms, shows, and other indoor situations require vaccinations for workers and customers. City educators and hospital staff should also be vaccinated.
At the federal level. On September 9, President Biden announced mandatory vaccination for most federal employees. This mission applies to employees of the White House and government agencies, including all federal and military officials.
it is the private sector. Biden requires all companies with 100+ employees to require weekly vaccinations or tests to support the company’s new vaccination policy. Several companies such as United Airlines and Tyson Foods were in debt before Biden’s announcement.

“We really don’t know why some people distribute too much and others don’t,” says Dr. Radawara. “There’s a lot of heterogeneity between individuals.”

Data from more participants would be more convincing, but two studies taken together suggest that increased aerosol-mediated transport contributes at least in part to mutant infectivity. He said he did.

For Dr. No one is involved in Munster’s work, but the Syrian hamster is involved. With the help of animals, the team was able to tightly control the experimental conditions and focus solely on the movement of the aerosol, said Dr. Munich.

The researchers divided a pair of hamsters into tubes of different lengths that allowed air to flow but did not allow body contact. They examined how well the different variants migrated from infected “donor” hamsters to uninfected “wake up” hamsters.

If the cells are more than 2 meters apart, only the smallest aerosols (particles smaller than 5 micrometers) will infect the guard hamster. And as expected, the team found that the alpha variant outperformed the original virus in infecting the guard hamsters.

The results are sent to bioRxiv, a website that posts articles before they are published in scientific journals.

Researchers are currently testing delta mutants and hope to find them more effective, said Dr. Munich.

Together, the new findings underscore the importance of vaccination masks