What does it mean that covid is airborne? — Vophs

Covid, it is now an established fact, is airborne.

Like other infectious diseases such as measles, chicken pox, or tuberculosis, it is spread by aerosols that can stay airborne for long periods of time, and travel long distances. The airborne quality of the virus is recognized by public health officials as well. World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC).

Yet when the virus emerged, and for some time afterward, public health officials instead thought the virus could spread through large droplets, which unlike aerosols can only travel about two meters, and land on nearby surfaces. can, which in turn become potential vehicles. transition. It was the theory that had everyone cleaning out their groceries and wondering whether to sanitize their mail in the early 2020s.

Although aerosols and drops may look similar, their public health effects are very different. The assumption that Covid is spread through droplets informs public health advice such as emphasizing the importance of social distancing, wearing any type of mask, including cloth, and disinfecting surfaces — focusing on high-quality masks. As opposed to concentrates that can block aerosol transmission (such as N95s) and ventilation.

But the evidence that Covid was airborne was initially overwhelming – what was lacking was that. Willingness to accept it. The WHO labeled the airborne transmission theory as misinformation, and worked to dispel it, sharing it on social media. Media channels: “#Fact: #COVID19 is not airborne.”

Yet in early April 2020, a team of scientists presented WHO with evidence of aerosol transmission of Covid, gathered by studying the transmission dynamics of some superspreader events. “I said OK, we’ll explain it to them, and then as scientists we’ll have a reasonable discussion,” said Jose Jimenez, a chemistry professor at the University of Colorado at Boulder who was on the team. Renowned environmental physicist Lydia Morawska. “But he was completely closed off and rude, and he yelled at Lydia,” she said. It took almost two years for the WHO to admit that Morawaska was perfectly fine.

Jimenez, who had never worked on infectious disease before, was shocked. But their colleagues weren’t: The backlash they received tracked with a century-old history of public health opposition to the idea of ​​aerosol transmission — something Jimenez researched for a paper published this week. What was the beginning? International Journal of Indoor Environment and Health.

From miasma to contact infection

For most of human history, the idea that disease would travel through the air was uncontroversial. From Hippocrates’ miasma to the Persian physician Avicenna, the first theories of disease transmission included vague notions of foul fumes floating into people from an unhealthy environment.

It was not until the second half of the 17th century that the discovery of bacteria and microorganisms led to the understanding that disease could also be spread from person to person. As a result, the paper noted, there was a long debate between the so-called “contagiousists,” who believed that diseases spread from person to person, and the “miasmetists,” who believed in airborne contagion. have Later discoveries, including the germ theory, fed into one camp or the other by the turn of the century, and the work of Charles Chaplin, an American epidemiologist.

Chaplin’s experiments showed that germs could be transmitted by direct contact, but he found that the persistent belief in exclusively airborne transmission was an obstacle to controlling diseases that spread by contact infection. “If a sick room is full of floating contagion, what is the point of trying as much as possible to avoid contact infection? […] It is impossible, as I know from experience, to teach people to avoid contact infection while they firmly believe that air is the greatest vehicle of infection,” he wrote in 1914. Journal of the American Medical Association (JAMA).

As more information was gathered about disease vehicles such as cholera (water) or malaria (parasites), Chaplin eventually concluded that airborne transmission was unlikely in most scenarios. As Jimenez and his colleagues put it in the paper, it turned the absence of evidence for airborne transmission into evidence of its absence. In his writings, the newspaper reported, Chaplin advocated “abandoning airborne transmission as a working hypothesis and focusing our attention on the prevention of contact infection.” He saw the paradigm shift as a historic step, and considered the idea of ​​aerial delivery to be little more than folklore. “It would be a great relief to most individuals to be freed from the specter of infected air, a specter that has haunted the race since the time of Hippocrates,” he wrote.

This resulted in an over-correction, led by so-called reformers who embraced Chaplin’s new paradigm. “They kind of showed that the miasma was wrong and then they said, it’s not going to be us, it’s superstition, it’s something we have to overcome,” Jimenez said.

Annoying little droplets.

The dismissal of aerosol transmission as superstition carried a strong emotional charge that is still felt today. To explain disease transmission without direct contact, preference shifted to the theory that pathogens would be transmitted by large droplets. Initially accused of spreading covid.

Indeed, Covid is not the first case where scientists have had to fight their way to the entrance of aerosol transmission. Droplets were initially thought to be the cause of non-contact transmission of tuberculosis, measles and smallpox, and only after incontrovertible evidence would the scientific establishment acknowledge the existence of aerosol transmission.

“Something they told us at the WHO meeting is, ‘Covid [was] Not from the air like measles, if it was like measles we’ll see.’ But originally measles and chickenpox, both highly contagious diseases, were described as droplet diseases until the 1980s,” Jimenez said.

What’s more, he said, while much effort goes into proving each instance of aerosol transmission, not enough attention is paid to the fact that there is no solid evidence for droplet transmission. “Droplet transmission, which they told us and still tell us, is the primary method. [covid] transmission, it’s never been directly demonstrated — not just for Covid, but for any disease in the history of medicine,” Jimenez said.

Aerosol scientists believe there is a Misunderstanding of physics in theory of droplet transmission, but resistance remains strong among public health officials. “Over the past two years, there has been much debate about the modes of transmission of COVID-19, particularly the way SARS-CoV-2 is transmitted through the air. […] This is a cross-cutting issue related not only to SARS-CoV-2 but also to other respiratory pathogens that are capable of creating public health emergencies of international concern,” said WHO spokesperson Margaret N. “WHO is now leading and coordinating an international technical consultation process to discuss this issue with global experts and reach consensus,” read a statement Harris shared with Vophs.

Sickness in the air

Acknowledging airborne transmission has implications that go beyond epistemic medicine, or dogma. If a disease is spread by direct contact or proximity, the responsibility to prevent it may be imposed on the individual. Protective gear, distancing, disinfection: these are all steps people can take to prevent an outbreak. Thus, getting sick becomes a personal failure—people may not have washed their hands, or omitted certain precautions.

But if the virus is airborne and someone gets infected in a school or office, where they cannot control the air quality, the blame cannot be personal. Similarly, any face covering can prevent large droplets, but if specific types of masks (such as N95 respirators) are required, institutional involvement is greater in ensuring that they are affordable. , are available and match certain quality standards. “Institutions — the CDC, the government, the WHO — are confused because it’s so simple,” Jimenez said.

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