Recall from the previous lessons, that once a person gets infected, they are first asymptomatic, meaning there are no symptoms of illness and the only way to tell if someone has SARS-CoV-2 is to perform a reliable laboratory test. At some time after the infection a person starts experiencing symptoms and develops a disease COVID-19.
But there are people, who despite the infection, never develop the disease and stay asymptomatic all the time. These people become asymptomatic carriers of the virus.
What was of interest before is whether asymptomatic cases can infect others? Some viruses only become transmissible human-to-human after the infected person starts showing symptoms. Unfortunately, this is not the case for the current pandemic. Asymptomatic person are contagious to others.
This is a big question for us looking for the future of the disease development. We already suspect that the virus will stay with us for longer, perhaps forever. So how can we treat asymptomatic carriers? Since vaccination can’t be applied to already infected people, but the virus is not fought by the immune (otherwise there would be symptoms) will virus survive forever in these people?
And what if the virus mutates? Vaccination then becomes ineffective, such as the case with seasonal flu. Flu virus mutates every time it comes back, so vaccines are often not effective enough.