Dr. John Ioannidis, COVID-19 Serology Study: Fatality Rate Similar to Flu
April 19th, 2020Via: Medrxiv:
A hundred deaths out of 48,000-81,000 infections corresponds to an infection fatality rate of 0.12-0.2%. If antibodies take longer than 3 days to appear, if the average duration from case identification to death is less than 3 weeks, or if the epidemic wave has peaked and growth in deaths is less than 6% daily, then the infection fatality rate would be lower.

This study puts the prevalence rate at 6 % at most, invalidating the circulating idea that in California the coronavirus spread earlier, unnoticed.
Although the weather could also be a major factor, this opens the way for a possible explanation of the low death rate :
Asymptomatic rate estimates vary (20 % to 75 % or more). It seems people infected by asymptomatic carriers are themselves more prone to be asymptomatic, for reasons unknown. Possibly the virus is a different version, possibly it’s the lifestyle, possibly immunity is somehow transferred.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3565270