Fig. 1.

Epidemic curve of a norovirus outbreak in a high school, Lleida, Spain (n = 39). ^a Subtraction of the minimum incubation period (–24 h) from the first case in the epidemic curve. ^b Subtraction of the maximum incubation period (–48 h) from the last case in the epidemic curve. ^c To calculate the days of transmission, we determined the time between the dates resulting from subtracting the minimum incubation period from the first case [23 January (23/1)] in the epidemic curve and the maximum incubation period from the last case [26 January (26/1)].