The influential Italian newspaper Corriere della Sera published a large material summarizing the difficult pandemic experience experienced by this country. In particular, the publication explained how and when COVID-19 can be infected and how to reduce risks. A resident of Rome and a popular blogger Slava Shvets translated the most important places from this material:
“Most of all they get sick within the family. That is, should someone get sick, and the risks for everyone else living in the apartment increase dramatically (see graph)
Is it possible to get sick by catching a walk, waiting in line, or picking up a parcel from a courier? Unlikely.
For infection, you need to undergo a certain viral load. Judging by other, more studied coronaviruses, this is a small load (that is, these viruses are quite contagious and tenacious).
By some estimates* about 1,000 virus particles are sufficient. This is a preliminary assessment, which can be confirmed or refuted, but the article stipulates that they use this data as an example for illustrative purposes.
In the toilet
A lot of surfaces that need to be touched - door handles, locks, taps, buttons of dryers (if not automatic, etc., etc.) That is - there are a lot of places where the virus may appear after touching. It is still not very clear what exactly the amount of virus is contained in the secretions, but it is absolutely known that the toilet flush works like an aerosol, "spraying" drops of water around itself after discharge. Therefore, before the appearance of new and accurate research data, it is worthwhile to be very careful about public toilets (and even at home if someone is sick at home).
A coughing fit is about 3,000 drops of saliva flying at a speed of 80 km / h. The heaviest will fall to the ground, the lightest will remain in the air for some time and these latter can cross the room in a few seconds.
There are already about 30,000 drops and a speed of 300 km / h. If a person is contagious, then from one sneeze in the air will be up to 200 million particles of the virus. (to the question of why to wear masks in public places).
One breath, depending on speed and depth - from 50 to 5000 drops. If you breathe through your nose, then even less. And the less deep breaths - the fewer particles of the virus in the drops - and the less the viral load from breathing. We do not have data on covid, but there is data on the flu - from the breath of a person with the flu, it makes a viral load of 33 virus particles per minute.
Infection = particle count x time
That is, if someone sneezes and coughs right in front of you - this is immediately a 200 million viral load and a very high probability of getting sick. A high probability is to enter a room where, for a minute, someone sneezed or coughed.
If the patient just breathes shallow next to you - 1000 particles divided by 33 particles per minute - it will take about half an hour to get infected.
If the patient does not just breathe, but also says, then this is a load of about 200 particles per minute, that is, 5 minutes is enough.
About 44% are asymptomatic carriers. People of different ages spread a different viral load (second schedule) and this depends not only on age, but on individual characteristics.
Based on the available data, 20% of patients leave 99% of the viral load on the premises (I understood this part as the fact that there are those who infect more and those who are carriers, but hardly infect - see the link in the comments).
Closed rooms and air conditioners are evil, because in closed rooms, infections occur quite easily. (What to do when the summer is over and you have to be in these rooms is incomprehensible)
The main infections occur indoors - where people were close to each other and said, sang or shouted.
There is no data on infections in stores so far (and this is good news).
Less than 0.3% is due to infections outdoors.
That is, following the formula, it is worth thinking about the amount of air in the rooms, if in doubt - stay there for less than 5 minutes and generally limit all doubtful moments to these 5 minutes..."