Sources

Case and death data come from the country and US state pages on Wikipedia, linked from:
https://en.wikipedia.org/wiki/COVID-19_pandemic and https://en.wikipedia.org/wiki/COVID-19_pandemic_in_the_United_States.

Annual cold-and-flu season data for countries is from World Health Organization data aggregated at:
https://www.worldlifeexpectancy.com/cause-of-death/influenza-pneumonia/by-country/.

World population and demographic data is from the CIA Factbook, at:
https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html.

United States population and demographic data is from the US Census, at:
https://www.census.gov/quickfacts/fact/table/US/PST045219.

GDP data for countries is from:
https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal).

PM2.5 pollution data for countries is from:
https://ourworldindata.org/outdoor-air-pollution.

United States mortality data is from CDC Wonder, at:
https://wonder.cdc.gov/ucd-icd10.html.

United States Covid-19 place-of-death data is from the CDC NCHS, at:
https://data.cdc.gov/NCHS/Provisional-COVID-19-Death-Counts-by-Place-of-Deat/uggs-hy5q.

United States Covid-19 hospitalization rate data is from the CDC COVIDNet, at:
https://gis.cdc.gov/grasp/COVIDNet/COVID19_3.html.

Historical pandemic data is from:
https://en.wikipedia.org/wiki/List_of_epidemics.

Historical world population data is from:
https://www.worldometers.info/world-population/world-population-by-year/.

US EIA Heating Degree Days data is from:
https://www.eia.gov/totalenergy/data/annual/showtext.php?t=ptb0107.

US CDC Covid-19 demographic data is from:
https://data.cdc.gov/NCHS/Provisional-COVID-19-Death-Counts-by-Sex-Age-and-W/vsak-wrfu/data.

US CDC annual Pneumonia and Influenza demographic data is from:
https://www.cdc.gov/nchs/data/nvsr/nvsr68/nvsr68_09-508.pdf.

Thailand Covid-19 demographic data is from:
https://en.wikipedia.org/wiki/2020_coronavirus_pandemic_in_Thailand.

Switzerland Covid-19 demographic data is from:
https://en.wikipedia.org/wiki/COVID-19_pandemic_in_Switzerland.

US Covid-19 hospitalization data is from:
https://gis.cdc.gov/grasp/COVIDNet/COVID19_5.html.

US CDC flu vaccine data is from:
https://www.cdc.gov/flu/vaccines-work/past-seasons-estimates.html.

US State lockdown data is from:
https://en.wikipedia.org/wiki/U.S._state_and_local_government_responses_to_the_COVID-19_pandemic.

US Actual Causes Of Death Blamed On Covid-19 is from:
https://data.cdc.gov/NCHS/Conditions-Contributing-to-COVID-19-Deaths-by-Stat/hk9y-quqm/about_data.