[Waterborne outbreaks in Norway 2003-2012].
BACKGROUND
We describe the status of waterborne outbreaks notified in Norway and discuss this in the context of outbreaks recorded in previous years, to gain a better understanding of their development in Norway in recent years.


METHODS
We have collected information on all outbreaks notified to the Norwegian Institute of Public Health via the surveillance system for communicable diseases in the ten-year period from 2003-2012 for which drinking water was given as the suspected cause.


RESULTS
Altogether 28 waterborne outbreaks with a total of 8,060 persons reported as ill were notified in the period. The majority of outbreaks resulted in fewer than 100 cases of illness. There were two outbreaks with more than 1,000 cases of illness: an oubreak of campylobacteriosis in Røros and an oubreak of giardiasis in Bergen. In more than half of the outbreaks, water was supplied from public water distribution systems (16/28 outbreaks, 57%). In addition, a large proportion was linked to individual households with their own water supply (12/28 outbreaks, 43%).


CONCLUSIONS
Most of the outbreaks in the ten-year period were linked to public water distribution systems, while almost half were linked to non-disinfected water supplies to individual households. Although most of the outbreaks were small, two extensive outbreaks were also registered in the period, resulting in more than one thousand cases of illness. This underscores the need for good contingency planning and surveillance, so that suspicion of waterborne outbreaks is rapidly notified to the responsible authorities, and the importance of good protection of water sources, as well as proper maintenance of water treatment plants and distribution systems.
Divisjon for smittevern Nasjonalt folkehelseinstitutt.
Bernardo
B
Guzman-Herrador
Divisjon for smittevern Nasjonalt folkehelseinstitutt og Avdeling for biostatistikk Oslo senter for biostatistikk og epidemiologi Institutt for medisinske basalfag Universitetet i Oslo.
Birgitte Freiesleben
BF
de Blasio
Divisjon for miljømedisin Nasjonalt folkehelseinstitutt.
Vidar
V
Lund
Divisjon for smittevern Nasjonalt folkehelseinstitutt.
Emily
E
MacDonald
Divisjon for smittevern Nasjonalt folkehelseinstitutt.
Line
L
Vold
Region midt Mattilsynet.
Erik
E
Wahl
Divisjon for smittevern Nasjonalt folkehelseinstitutt.
Karin
K
Nygård
D002169:Campylobacter Infections / Q000453:epidemiology; D004196:Disease Outbreaks; D060766:Drinking Water; D062665:Epidemiological Monitoring; D005873:Giardiasis / Q000453:epidemiology; D006801:Humans; D009664:Norway / Q000453:epidemiology; D062486:Public Health Surveillance; D014871:Water Microbiology; D014881:Water Supply / Q000592:standards; D000069578:Waterborne Diseases / Q000453:epidemiology*
D060766:Drinking Water