Acute disease is disease that comes on suddenly, such as is found in the middle of an epidemic. But when it comes to epidemiology, the perspective of history is crucial.
Though acute respiratory disease is capable of causing up to a 50% increase in “respiratory deaths,” because those respiratory deaths are just a fraction of total deaths, the increase in all-cause death (beyond what had been expected) is somewhere from about 4% excess up to a maximum of about 8% excess death.
Here is the crude death rate for the USA from 1960 forward, with a note about the 1968 flu pandemic coinciding with a 4% increase in all-cause death — the highest percentage increase in death from 1960 going forward (until the still-mysterious “COVID”):
Because acute disease is capable of causing up to a maximum of about 8% excess all-cause death — even including the 1957 flu pandemic, which had higher case fatality rate than the 1968 Hong Kong Flu — then if death rates ever remain 20% higher than baseline for multiple years, it indicates that the excess death is being caused by something other than a respiratory virus.
To repeat, a respiratory virus is something which could possibly increase all-cause death by somewhere from 4% up to about 8% maximum — but the excess death rates seen in so many places of the world right now are beyond (or outside of) the history of epidemiological outcomes in modern society.
If history reveals that respiratory diseases do not increase all-cause deaths by over 8%, then we need an explanation for recent increases which have remained beyond 8%.
Reference
[cumulative three-year excess from 1957 Asian Flu was 14%, or ~4.7% per year] — Viboud C, Simonsen L, Fuentes R, Flores J, Miller MA, Chowell G. Global Mortality Impact of the 1957-1959 Influenza Pandemic. J Infect Dis. 2016 Mar 1;213(5):738-45. doi: 10.1093/infdis/jiv534. PMID: 26908781; PMCID: PMC4747626. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4747626/