Outbreaks have been reported in hospitals, day-care centres, within households, among bathers (affecting participants in water sports in lakes and swimming pools), and in municipalities with contaminated public water supplies.
Haiguspuhanguid on esinenud haiglates, lasteaedades, elamutes, suplejate (sh veesportlaste) seas (järvedes ja ujulates) ning saastunud veevarustusega piirkondades.