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Have you ever wondered how many viral particles are in the body of a person infected with the coronavirus? Scientists have done the math.
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The Israeli and American researchers tried to calculate the number of virions present in the body of a person infected with the coronavirus SARS-CoV-2. Obviously they didn’t count them one by one, but with some calculations they managed to get a reliable estimate. They share their result in a publication just for the moment broadcast by MedRxiv.
The first calculation concerns the total number of viral particles present in the body, whether they are viable or not. To do this, they used data published in a study that estimated the number of copies ofARN per gram of tissue in different organs (lungs, trachea is bronchi, tonsils and lymph nodes, digestive system) in macaque rhésus.
Up to one hundred billion virions in the body of an infected person
To relate it to the human being, they multiplied by the mass of each organ. For example: there are between 106 and 108 copies per gram of lung in the rhesus macaque. Human lungs weigh around 1 kg, on a donc 109 and 1011 copies of RNA in the lungs of an infected person.
This figure includes both viral particles contagious and those that are not. To realize the number of actually infectious viral particles, the researchers carried out the same reasoning but taking into account the TCID50 which allows to determine the titer, or concentration, of infectious virions. In the lungs of rhesus macaques, it was estimated to be 102 to 104 per gram of fabric. Multiplying again with the mass of the human lungs, we get 105 to 107 infectious viral particles in the lungs.
The researchers also put forward a rather surprising figure: if we weighed all the virions present in the body of an infected person, the scale would show between 1 and 100 µg. Compared to the number of infected people in the world, the data obtained shows between 0.1 and 1 kilo coronavirus !
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