in ‧ ci ‧ dence AC /ˈɪnsəd ə ns, ˈɪnsɪd ə ns/ BrE AmE noun [countable usually singular] formal
the number of times something happens, especially crime, disease etc ⇨ rate
incidence of
Why did the incidence of heroin use continue to climb?
high/low etc incidence
Smokers had the highest incidence of colds.