Unless I'm reading that chart wrong it seems like flu went away but viruses that cause cold like symptoms stuck around.
If masks/etc was super effective wouldn't you expect those to go down with influenza?
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."
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...
Viruses are not identical.
https://en.wikipedia.org/wiki/Rhinovirus
> They are lytic in nature and are among the smallest viruses, with diameters of about 30 nanometers. By comparison, other viruses, such as smallpox and vaccinia, are around ten times larger at about 300 nanometers, while flu viruses are around 80–120 nm.
Different virus sizes, different mask effectiveness.
Anecdotally, my kids are in middle school, and every winter we get several colds. None this year.
Not necessarily - when speaking and otherwise spreading aerosols they start out much larger than any virus particles contained within them and quickly dry out and shrink if in air (i.e. not caught in a mask) [1, 1um - 500um, between Table I & Fig 11].
If they were on their own, the small 'nanoparticle' regime (1-100nm) shows fairly good filtration in a variety of media [1st image in 3] thanks at least in part to the diffusion of particles through filter media. It's not the same by size by any means (with smaller often being the most passed particle size) but it varies with filter construction and treatment [3].
[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8061903/ [2]: https://www.tandfonline.com/doi/pdf/10.1080/00022470.1980.10... [3]: https://academic.oup.com/annweh/article/56/5/568/159920
Many cold-like viruses infect mucous membranes (you have a number over your body). A glancing touch is enough to be infected.
https://www.usatoday.com/story/news/nation/2020/09/08/do-you...
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...