THE PROBLEM: sharing the air with any infected. The realistic solution: ventilate as much as possible, create air currents, use air filters, distance yourself and protect yourself with masks. On the coronavirus and airborne contagion is multiplying the interventions and clarifications in scientific journals. But now, from this Monday, after the singular turnaround in mid-October, the CDC, Centers for Disease Control and Prevention, the most important public health control body in the United States, declare that, especially in enclosed spaces without adequate ventilation, the Airborne transmission occurs and the cause would be the greater concentration of the virus that we could breathe. The tiny droplets and particles that float in the air for minutes and even hours would play a role in the pandemic.
Coronavirus, how safe are cloth masks
by IRMA D’ARIA
25 September 2020-
Two weeks ago in the FAQ (Frequently Asked Questions) on the CDC website in the question “How does Covid-19 spread?” it had appeared, for the first time, that the coronavirus it is transmitted “in the most common way” by “breathing in droplets or small particles, such as those in aerosols, produced by an infected person when they cough, sneeze, sing, speak or breathe. These particles can be inhaled into the nose. mouth, airways and lungs causing the infection “. And he added: “There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others and travel over two meters (for example when singing in a choir, in restaurants or in gyms). In general, indoor environments without good ventilation increase the risks “. This answer had been on the site for a weekend, since Friday; on Monday, the previous answer which spoke only of droplets was restored, recommending the spacing of six feet (1.8 meters). The CDC claimed that the information was published in error. Now the new version, or inversion.
Winter indoors
The British Medical Journal, on October 18, he realized it immediately reporting the case. The problem would have been that specification of the “most common mode” which could be interpreted as the “main mode of transmission”. No: are the largest drops emitted when someone infected coughs, sneezes, sings, talks or breathes the main vehicle of viral spread. But now it is added, under the title “Covid-19 can sometimes be transmitted by air”: «Some infections can be spread due to exposure to the virus in small droplets or particles that can remain in the air for minutes or hours. These viruses are capable of infecting people even at distances greater than two meters or after the infected person has left the room. It is called airborne transmission and is an important route by which tuberculosis, measles and chickenpox spread. ‘ It should be noted that TB is caused by a bacterium and not by a virus such as measles or chickenpox. The explanation then continues: “There is evidence that under certain conditions, people with Covid-19 have infected others who were beyond 1.8 meters away. Such transmissions occur in enclosed spaces that have inadequate ventilation. Sometimes infected people breathed heavily, for example while singing or exercising. “It would be a matter of getting the virus more concentrated enough to be passed on to others. This would have happened when space was shared but also when the person with CoVid-19 had just left the closed room.
The masks? They work like the vaccine
by GIUSEPPE DEL BELLO
September 28, 2020-
The cold
The Bmj, in the first article two weeks ago, he rightly recalled the implications of all this when entering the winter season with a greater presence in closed rooms. Jose-Luis Jimenez, a chemist professor at Colorado Boulder University, recalled a case in point that happened in March in Washington state in a choir class. Indoor singing rehearsals infected 53 of the 61 choir members after singing together for two and a half hours. “People who were 50 feet (over 15 meters) away from the person who was contagious became infected.” In the FAQ of the Istituto Superiore di Sanità, Epicentro, the answer to the question of transmission is clear-cut: “The preeminent mode of contagion to date is related to the transmission of the virus through the droplets of saliva emitted by people infected with coughs, sneezes or speaking. This ascertained mode of transmission ends in about a meter away “. To then continue: “to date there is no scientific evidence of the permanence of the new coronavirus in the air beyond the safety distances mentioned above under normal conditions, or in the absence of systems that produce aerosols that can instead be found in a hospital environment in the assistance to Covid-19 patients “. However there are studies, the ISS is quick to clarify. One last on Jama Internal Medicine by the University of Georgia and indoor aerial transmission. Researchers studied a CoVid-19 outbreak in a Chinese community by linking it to a patient who reportedly spread the virus to colleagues on the bus via the air conditioning system. Ye Shen, associate professor of epidemiology and biostatistics at UGA College of Public Health, and colleagues in the study followed the traces of the outbreak by arriving at two buses, closed windows and air conditioning, on one of which the infected patient had traveled. Most of the passengers on that bus were infected. And it wasn’t just those sitting next to the patient. Epidemiological considerations: good aeration / ventilation and use of masks indoors is required.
Coronavirus, with or without symptoms the viral load is the same
by IRMA D’ARIA
23 September 2020-
Thresholds of droplets
In such a situation also comes a letter about Science of five leading US researchers, first signatory Kimberly Prather, an atmospheric chemist at the University of California San Diego. “There is an urgent need to harmonize the discussion about how the virus is transmitted across disciplines to ensure the best control strategies and to deliver clear and consistent guidelines for the public.” The discussion leads back to the distinction between aerosols and droplets using the 100 micrometer threshold. Not the historical one of 5 micrometers, the specialists add in the letter. The 100 micrometers would separate the aerodynamic behavior of the droplets: below this threshold the virus remains in the air even for hours. To understand even better: the famous fine powders, PM10 for example, are in the order and less than 10 micrometers. The distinction concerns the behavior of air droplets emitted by an infected: the largest virus drops fall to the ground in a few seconds, the smallest, nebulized (aerosol) ones can float and travel in the air from several seconds to hours and can therefore be inhaled from others even relatively distant. They infect people close to but also over two meters away. “Highly more likely to be infected by aerosols than sprayed by droplets,” the researchers write. The public health authorities – is the appeal of the letter – must give clear indications on mobility outside and inside the premises, improving internal ventilation and the protection of high-risk workers.
Drastic measures?
Many specialists invoke (already in July also a comment onClinical Infectious Diseases ) much stricter preventive measures. In Italy, doctors Giampaolo Mezzabotta and Claudio Marra first raised the question, both with extensive experience in countries where epidemics of viruses and bacteria have always been fought. Since the beginning of April, the two doctors have created, with the contribution of Fabrizia Del Greco, also a project manager of NGOs in Africa, an information site on Facebook with a page called “New air – The importance of air exchange in the premises “. https://www.facebook.com/Apriamolefinestre/
The position of the WHO
It is so evident that in unventilated rooms, where several people stop without a mask, the chances of contracting the virus multiply. The World Health Organization says it: People must avoid “confined, confined spaces with little ventilation. Gather outdoors whenever possible.” The mask obviously makes the difference. Even if it is not the panacea. On the website of the Federation of the Order of Doctors it is well explained and repeated: there are two types of masks, the surgical one and the N95. The first “designed above all to protect not so much who is wearing it, as the people around (…) The other type of mask, N95, is a more sophisticated protection device, which should be able to filter at least 95 % of particles suspended in the air, including the possible presence of the coronavirus (…) but in reality both types present a series of criticalities. New Scientist, for example, we read that even in the best of cases “wearing a mask can help, but it does not guarantee total protection”. Furthermore, N95 respirators cannot be used by individuals who have beards or by children ». But the current and realistic recipe is as follows: mask (N95 better), distance, ventilation, air filters.
Are you sure?
And an article appeared in the magazine on air filters Jama concerning the safety of air travel during the pandemic has caused debate. The conclusion would be: the risks of contracting Covid-19 during a flight is less than staying in offices, classrooms, supermarkets or commuter trains.
Air in aircraft enters and exits the cabin near the various rows making it difficult to transmit respiratory particles between the rows. Furthermore, the air flow is much faster than that existing in a normal building: half comes from outside, half is recycled through HEPA filters, the same used in operating rooms. If a passenger remains seated and stationary, it is almost impossible to have face-to-face contact with other passengers during the flight. Despite the large number of passengers, confirmed cases of transmission are very low: 42 in total in the US. In China, a similar study on high-speed trains confirmed 2,300, 0.3% of all passengers. Wearing the mask is the best thing to do. Also, wash or disinfect your hands frequently and avoid touching your face. So the article on Jama. But the comments were very critical: not all planes have HEPA filters, only those from 1990; the distance between passengers is insufficient and there is no obligation for the mask; on flights lasting several hours, food is provided and the mask is removed.
There are also those who, an engineer specialized in ventilation, dispute the effectiveness, in the event of sneezing, coughing or speaking, of the ventilation in the cabin. Others report that the planes in reality are different from the “ideal” ones, that HEPA filters are positioned only in certain places and sometimes some objects obstruct their good functioning, often they are not in operation during the entire boarding phase, maintenance does not is always correct, not all HEPA filters are the same and of the highest quality.
A curiosity comes from the study that appeared on Physical Review Fluids which concerns the flow of air caused by normal daily conversation, considered a transmission route. Cornell University researchers have realized that the articulation of consonants such as P or B brings the emission of saliva and mucus to at least one meter in front of the speaker. In a further experiment, the researchers showed that ordinary cocoa butter on the lips reduces the droplets contained in the stream emitted by speech.
–
