noun
Used in medical, epidemiological, and public health contexts to describe the proportion of a population that becomes infected.
この地域の感染率は先月より下がった。
The infection rate in this area has dropped since last month.
ワクチン接種が進むにつれて感染率が低下した。
As vaccination progressed, the infection rate decreased.
陽性率 refers specifically to the 'positivity rate' of tests, while 感染率 refers to the actual infection rate in a population.
Compound of 感染 (kansen, 'infection') and 率 (ritsu, 'rate').