Results and discussion
The risk of bilateral pneumonia (Fisher’s exact test; 31-530 older vs
22-322 younger, p>0.05) and the duration of symptoms (ANOVA
p>0.05) did not increase with age although, as expected,
older patients presented higher disease severity (mean 2.59±0.13) than
younger ones (mean 1.58±0.11; U-test, p<0.001)(Wu et al.,
2020a; Zhang et al., 2020). However, the mean of both disease severity
(U-test, p=0.006) and duration of symptoms (ANOVA, p<0.001)
declined over time. This decline was unexpected and was not driven by
changes in patient age structure (Figure 1). It was also not driven by
changes in temperature or precipitations (Wu et al., 2020b; see
supplementary information file). From the initial outbreak period (weeks
10 to 12, 2020; n=36 cases) to the advanced period (weeks 13 to 19; n=17
cases) the mean severity declined by 34% and 21% in younger and older
patients, respectively. The mean duration of symptoms (21 days, range
4-67) was 59% and 60% shorter in the advanced period in younger and
older patients, respectively, as compared to the initial period.