The opposite trend occurred for SARS (in the same class as nCoV-2019), which originally had around a 2-5% deaths/cases rate but ended up with >10% once all cases ran their full course.
SARS was very unusual, and serves as a partial counterexample. On the other hand, the “trend” being shown is actually almost entirely a function of the age groups of the people infected—it was far more fatal in the elderly. With that known now, we have a very reasonable understanding of what occurred—which is that because the elderly were infected more often in countries where SARS reached later, and the countries are being aggregated in this graph, the raw estimate behaved very strangely.
Estimate of swine flu fatality rate was ~0.5% in July 2009 with 100,000 cases reported. It ended up dropping over an order of magnitude.
The opposite trend occurred for SARS (in the same class as nCoV-2019), which originally had around a 2-5% deaths/cases rate but ended up with >10% once all cases ran their full course.
SARS was very unusual, and serves as a partial counterexample. On the other hand, the “trend” being shown is actually almost entirely a function of the age groups of the people infected—it was far more fatal in the elderly. With that known now, we have a very reasonable understanding of what occurred—which is that because the elderly were infected more often in countries where SARS reached later, and the countries are being aggregated in this graph, the raw estimate behaved very strangely.