>>13268134Climate factors such as average temperatures and yearly sun angle regarding vitamin d generation.
Local plant species which might cause more or less irritation from their pollen or species of tick or mosquito and potential infections people living there might pick up over their lives that could alter their immune responses
Demographics - skin color correlates to vitamin d again, also cultural differences resulting in different diets. Age of populations, how the populations are considered (population density, not just overall for the state but a county by county or even city/town by city/town comparison).
Local social customs that might cause different behaviors.
Past industry which could contribute to environmental contaminants having health impacts
Mineral composition of ground water and nutrients in local soil which can transfer to locally grown food
State building codes to see all allowed and banned substances as well as the actual difference in these environmental exposures in the population in practice.
Something like 'back in the 70s each state school system contracted with a different paint supplier' could lead to unique interactions with a virus 50 years later.
