Four years after the Covid has taken over the world, triggering an unprecedented pandemic, the WHO revised the terminology that identifies how respiratory infections are transmitted and has completely changed the rules relating to the contagion of the Sars-CoV-2 virus.
As the newspaper also reports Republic, the first most important consequence for the spread of respiratory diseases is the ventilation of closed environments. This condition was considered ‘secondary’ and underestimated after the outbreak of the pandemic.
Subsequently the WHO has identified three different ways of airborne transmission. The first is by air or inhalation, which is basically the main mode of transmission. In this case there is no longer a difference between small droplets that float (aerosols) or larger droplets that fall to the ground due to gravity (droplets), but we speak generically of infectious respiratory particles (IRPs, Infectious Respiratory Particles). A person emits respiratory particles of different sizes that can be inhaled and penetrate the upper respiratory tract of susceptible people, reaching the alveoli and lungs. Contagion by inhalation occurs over both long and short distances. Particles can accumulate remotely even for hours.
We also find the contagion by impact with deposition. The latter happens in this way: the particles emitted by an infected person, by gravity, are deposited on the mucous membranes (mouth, nose, eyes) of a susceptible person (the particles that were called droplets). But this type of transmission occurs only over short distances, the so-called “talking distance”. As for the “contact” transmission mode, it has been clarified that an infected person can transfer contaminated particles of any size and at any distance, generally through hands that come into contact with their own mucous membranes or across surfaces.
However, precisely to evaluate how quickly the virus responsible for the Covid disease is able to move between people in close contact or not, the WHO has made a web app called ARIA available to everyone, the function of which is to calculate the risk of contagion .
He spoke about the new transmission terminology Fabrizio Pregliascomedical director of the Galeazzi Hospital in Milan, who stated: “Between the rules on contagion followed to date and the new ones established by the WHO, the right measure lies in the middle“. “Over time, further investigation and clarification of the terminology adopted has become necessary – points out – . In reality, it has always been said that there was a double option: the SARS-CoV-2 virus is found in large and small particles. And the three types of respiratory contagion are still valid today: by air (inhalation), by impact with deposition and by contact. So I wouldn’t say that we did everything wrong, because even from a distance you can get infected“.
