Some viruses are known to compete in order to be the one that causes an infection. Research at University of Glasgow indicates that cold-causing rhinovirus trumps coronavirus. Benefits might be short-lived but rhinovirus is so widespread it could still help to suppress Covid.
Once a virus gets inside the cells in your nose, throat and lungs it can either allow in other viruses (which means that you end up with symptoms of both) or can prevent them entering.
Influenza is one of the most selfish viruses around, and nearly always infects alone.
Adenoviruses are more likely to allow another virus in. They are common viruses that cause a range of illnesses. They can cause cold-like symptoms, fever, sore throat, bronchitis, pneumonia, diarrhoea and pink eye (conjunctivitis).
Rhinovirus severely inhibits Coronavirus infection by triggering an immune response inside infected cells, blocking the ability of Covid to make copies of itself. So a high prevalence of rhinovirus in the population could stop new Covid infections. But Covid would be able to cause an infection again once the cold had passed and the immune response calmed down. Rhinoviruses are the most common cause of the common cold. A large rhinovirus infection may have delayed the 2009 swine flu pandemic in parts of Europe.
Source: Coronavirus: how the common cold can boot out Covid. BBC News item 23 March 2021 https://www.bbc.co.uk/news/health-56483445
