A bit of a scary paper. Flu viruses mutate a lot. Coronaviruses are generally more stable, but do mutate regularly. A Chinese team examined genetic differences in the viruses that affected a group of patients. Unfortunately they found that there were meaningful variations in some of the genes that impact infectiousness. So, mutation to more deadly strains is not out of the realm of possibility. (Medrxiv Paper)
The next paper uses information on health condition characteristics that make patients more vulnerable to coronavirus infection and illness to make updated estimates of coronavirus threat. (Medrxiv Paper) The researchers examined a number of countries, looking at age bands and known prevalence of certain conditions that are linked to greater risk of serious coronavirus. They estimated that about 22% of the global population is at some greater risk if they become infected because they have one of the conditions, around 6% have 2 or more of the conditions. Countries with older populations have larger percents at risk. For most of these people, the risk is only slightly elevated, but this kind of research can help shape policies about what sub-populations need special protection.
The next paper talks about a different way to estimate risk of death. (Medrxiv Paper) The researchers used data from the province of Ontario to estimate individual risks of dying from coronavirus. They used age and sex as variables to model risk once you had a confirmed diagnosis. From January 1 to April 15, Ontario had about 8500 confirmed cases; of which 385 people had died, 3902 recovered and the remainder were still in the disease process. Due to missing data only about 8400 cases were used in the analysis. Instead of calculating mortality as a percent of confirmed cases, the researchers calculated the mortality risk to individuals. The case fatality rate as traditionally calculated was 4.5%. The researchers calculated it as 3.1%. The biggest difference was in the 70 to 79 age group and the 80-89 group. The risk of death rose steadily with age. People under 40 had no risk of death. Males had a higher risk than females in every age cohort.