Fig. 1.
Annual distribution of cases categorised with high-virulent, low-virulent or unclassifiable Shiga toxin-producing Escherichia coli (STEC) infections notified to the Norwegian Surveillance System for Communicable Diseases (MSIS), 2007–2017 (N = 1458), and the number of HUSa cases (purple line, N = 67). The time periods when the majority of clinical medical laboratories in Norway introduced PCR detection of stx and implemented broad screening PCR in five of the laboratories are indicated with a black and grey arrow, respectively