[jvm_]

It seems there's a battle between virus's, they don't like sharing resources and the 'strongest' wins.

https://www.bbc.com/news/health-56483445

Coronavirus: How the common cold can boot out Covid

Think of the cells in your nose, throat and lungs as being like a row of houses. Once a virus gets inside, it can either hold the door open to let in other viruses, or it can nail the door shut and keep its new home to itself.

Influenza is one of the most selfish viruses around, and nearly always infects alone. Others, such as adenoviruses, seem to be more up for a houseshare.

If rhinovirus and Sars-CoV-2 were released at the same time, only rhinovirus is successful. If rhinovirus had a 24-hour head start then Sars-CoV-2 does not get a look in. And even when Sars-CoV-2 had 24-hours to get started, rhinovirus boots it out.

"Sars-CoV-2 never takes off, it is heavily inhibited by rhinovirus," Dr Pablo Murcia told BBC News.

He added: "This is absolutely exciting because if you have a high prevalence of rhinovirus, it could stop new Sars-CoV-2 infections."

[Pyramus]

It's very much disputed how much 'viral interference' was or is an influence in the current pandemic, and this effect (to my knowledge) has been only studied in animal models and human tissue [1], paper from the article [2].

Or to put it another way, the influenza season was already under way when SARS-Cov-2 hit in Feb 2020, but there is no indication the influenza virus slowed the SARS-Cov-2 pandemic.

The exciting thing about viral interference is that no genetic similarity between the viruses is needed, however, the effect is only temporary (days to weeks) and limited.

Unfortunately viral interference is also being misused as an 'alternative explanation' by folks that do not want to see the evidence that non-pharmacological interventions (hygiene, social distancing, quarantine, masks, large gatherings etc.) are effective against a whole host of respiratory diseases.

[1] https://en.wikipedia.org/wiki/Viral_interference [2] https://academic.oup.com/jid/advance-article/doi/10.1093/inf...

[bsimpson]

Begs the obvious question: could you intentionally infect someone with a mild, greedy virus to displace a more dangerous one?

[postalrat]

It seems possible. Timing would need to be right though so you would probably need to purposely infect that person with the dangerous one at the right time.