Droplets
The first form of coronavirus transmission identified is droplets of saliva expelled by an infected person when coughing, sneezing, but also when singing or speaking.
Scientists believe that this type of contamination happens with close contact, between a meter and a meter and a half away.
These droplets are, however, relatively "heavy", fall quickly, and are not suspended in the air.
Contacts and surfaces
The virus can also adhere to a dirty surface through droplets, such as hands, tissues, glass, taps, door handles, elevator buttons, or handrails. Here, the risk of contamination arises when touching the face after touching these surfaces.
The virus survives nine hours on the skin, compared with 1.8 hours for the flu virus, according to a Japanese study published in the journal Clinical Infectious Diseases.
The application of alcohol-based hand sanitizers, however, manages to neutralize the two viruses "in 15 seconds".
In a cool, dark environment, the SARS-CoV-2 coronavirus can survive up to 28 days on phone screens, glass, steel, and banknotes containing polymer plastic (found in Australia, Canada, and Britain, among other countries), according to a study by the Australian National Science Agency (CSIRO).
However, "this does not mean that this amount of virus can infect someone," Trevor Drew, director of the Australian Center for Disease Prevention, told public broadcaster ABC.
The main message remains that "infected people are far more contagious than surfaces".
"But it can help explain why, even when there are no more contagious people, sometimes [the epidemic] comes back even if the country is considered virus-free," he added.
Hence all should keep recommendations of not shaking hands, washing them frequently with soap or alcohol-gel, and regularly disinfecting surfaces, especially at work and in public places.
Aerosols
In closed, poorly ventilated areas, aerosols - clouds of microscopic droplets containing viral particles that are released only by breathing - can travel greater distances and land directly on other people's faces within a perimeter of up to 2 meters.
Those invisible clouds are suspected to remain in the air for minutes, or even hours, depending on available ventilation.
The United States Centers for Disease Control and Prevention (CDCs) recently updated their list of possible ways of spreading the coronavirus to include aerosols, although the main one, according to the CDCs, remains respiratory droplets in the form of saliva released by an infected person.
CDCs agrees with many scientists that this risk should be taken into account.
This mode of transmission "cannot be excluded", recognized the World Health Organization (WHO) in early July, mainly in "certain closed places, such as crowded and poorly ventilated places", and when people are present "for a long time ".
The dose of virus particles needed to cause infection is unknown, but the higher the dose, "the greater the likelihood of infection," Steve Nigelle, a virus geneticist at Harvard University, told AFP recently.
Implications for prevention
"There are three modes of transmission: droplets, aerosols, and displacements, without knowing the relative part of each one. Therefore, we have to maintain all the barrier gestures and open the windows," Professor Arnaud Fontanet, an epidemiologist at the Pasteur Institute, told AFP.
Air currents favors the dispersion of viral particles. And the message of continuously ventilating the environment also applies to the flu.
The main preventive measures are the use of a mask that covers the nose, mainly inside collective places, frequent washing of hands with soap, or alcohol-gel, and physical distance.
In outdoor environments, the use of masks in busy places is increasingly recommended.
Source: https://lifestyle.sapo.pt/saude/noticias-saude/artigos/os-tres-modos-de-...
