As part of the study, scientists analyzed saliva samples in 23 patients from two Hong Kong hospitals aged 35 to 75 years with positive results on coronavirus. It turned out that the number of viruses in saliva was the highest during the first seven days after infection, after which the rate gradually decreased.
The high viral load in the first week of the disease suggests that coronavirus is most actively transmitted from person to person even before the first symptoms of the disease are detected. After hospitalization, the possibility of viral infection is gradually declining, microbiologists say.
This study correlates with scientists’ claims that coronavirus mutated in order to infect more people before the first symptoms appear in patients. Compared to the first samples of the new coronavirus, a 382-letter-long nucleotide fragment disappeared from its genome next to ORF8, a special site in the coronavirus RNA that is responsible for starting the process of assembling protein N, one of the key components of SARS-CoV-2. It is this fragment of coronavirus that is associated with the copying of its RNA and the formation of new viral particles. A change in the genome made it less active in the first phases of infection and, accordingly, less noticeable for human immunity.