239 experts call for attention to aerosol transmission. Who: Reassessment

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 239 experts call for attention to aerosol transmission. Who: Reassessment


However, the letter entitled its time to solve the problem of new coronavirus aerosol transmission mentioned that more and more evidence has proved that the new coronavirus can adhere to aerosol particles in the air in indoor environment, and the floating time and distance are much longer than that of droplets. This has not been paid attention by who and major public health institutions.

Aerosol refers to the suspended particles in the air. The particle diameter is generally less than 100 u03bc M. PM2.5 is an aerosol. Virus aerosol transmission means that respiratory droplets lose water in the process of air suspension, and the remaining protein and pathogen constitute the nucleus, forming droplet nucleus, floating to the distance in the form of aerosol, and then infecting the human body through breathing.

In the new guidelines for the prevention and control of coronavirus, which was updated on 29 June, who still limited the conditions of aerosol transmission to special medical environments, such as endotracheal intubation, bronchoscopy, open suction, aerosol therapy, etc.

However, scientists believe that the spread of new coronavirus aerosol has long been widespread in daily life scenes, which is the only reason why there have been many super transmission events before.

According to the Los Angeles Times, at the end of March, 60 members of a chorus in Washington state of the United States rehearsed for two and a half hours. During the rehearsal, they strictly followed the regulations on disinfection and keeping a distance. Finally, 45 people were diagnosed and 2 of them died. But people involved in the rehearsal revealed that no one coughed or sneezed at the scene.

According to an analysis by Shelly Miller, a professor of mechanical engineering in Colorado, the United States, a large number of droplets released during singing increase the concentration of aerosol carrying viruses in the air, which is an important reason for the spread of the virus. The team believes that the new coronavirus in the air is no more infectious than smallpox, but undoubtedly the longer the exposure to the air with the virus, the greater the risk of infection.

However, it is much more difficult to prove the presence of viruses in the air than to detect them on the surface of objects. Milton pointed out that people inhale between 10000 and 15000 liters of air a day, and as long as there is a droplet nucleus in it, there is a risk of infection.

Linsey Marr, an expert on virus aerosol transmission at Virginia Tech University who signed the joint letter, said that previous who conclusions on low virus content in the air were based on research in hospital environment, but in fact, the ventilation rate of most indoor spaces is much lower than that of hospitals, creating conditions for virus accumulation.

If aerosol transmission is one of the main ways of new coronavirus transmission, wearing masks and other prevention and control measures are particularly important, even when maintaining a certain social distance. At the same time, schools, nursing homes, residential areas, office buildings and other indoor space also have restrictions on the use of fresh air system and air and other equipment to reduce air circulation. Ultraviolet lamps can also be used indoors to kill viruses floating in the air.

And scientists worry that the use of vacuum cleaners and the removal of protective clothing by medical staff may release aerosol carrying the virus.

In fact, the news that the new coronavirus can spread through aerosols has long been heard. A study published in the New England Journal of medicine in early March found that the virus can survive up to three hours in the air in a laboratory environment and half an hour in a clinical environment. Viral RNA was also found in the air of the corridor outside the hospital room where the new crown patient was admitted.

(function(){( window.slotbydup=window .slotbydup||[]).push({id:u5811557,container:ssp_ 5811557, async:true }However, according to who, many experiments on aerosol transmission are carried out under laboratory conditions and cannot reflect the real clinical situation. For example, the experiment in the new England Journal of medicine used aerosols to produce aerosols and then poured them into Goldberg drums to simulate cough. But the Goldberg drum is a high-power machine, which is actually an experimental induced aerosol production process. Paul Hunter, a member of the WHO infectious disease prevention and control committee and a professor at the University of East Anglia in the UK, said that the essence of aerosol transmission is droplet transmission. In the current resource shortage situation, it will only bring unnecessary pressure to impose strict prevention and control measures on aerosol transmission. According to the latest report of the Washington Post, a who spokesman said that he had learned about the joint letter through media reports and would send experts to reassess the relevant issues. The novel coronavirus pneumonia novel coronavirus pneumonia has been diagnosed more than 11 million 360 thousand. 532644 cases died. Over 13 countries have confirmed that thousands of cases have been diagnosed. India has been on the 3 day for a single day. The largest increase in the number of cases is 2 million 830 thousand days in the United States. The death rate of the new crown pneumonia is 129641. b6492

However, the who said that many of the experiments on aerosol transmission were carried out under laboratory conditions and could not reflect the real clinical situation. For example, the experiment in the new England Journal of medicine used aerosols to produce aerosols and then poured them into Goldberg drums to simulate cough. But the Goldberg drum is a high-power machine, which is actually an experimental induced aerosol production process.

Paul Hunter, a member of the WHO infectious disease prevention and control committee and a professor at the University of East Anglia in the UK, said that the essence of aerosol transmission is droplet transmission. In the current resource shortage situation, it will only bring unnecessary pressure to impose strict prevention and control measures on aerosol transmission.

According to the latest report of the Washington Post, a who spokesman said that he had learned about the joint letter through media reports and would send experts to reassess the relevant issues.