An extensive gastroenteritis outbreak after drinking-water contamination by sewage effluent, Finland.
An inappropriate cross-connection between sewage- and drinking-water pipelines contaminated tap water in a Finnish town, resulting in an extensive waterborne gastroenteritis outbreak in this developed country. According to a database and a line-list, altogether 1222 subjects sought medical care as a result of this exposure. Seven pathogens were found in patient samples of those who sought treatment. To establish the true disease burden from this exposure, we undertook a population-based questionnaire investigation with a control population, infrequently used to study waterborne outbreaks. The study covered three areas, contaminated and uncontaminated parts of the town and a control town. An estimated 8453 residents fell ill during the outbreak, the excess number of illnesses being 6501. Attack rates were 53% [95% confidence interval (CI) 49.5-56.4] in the contaminated area, 15.6% (95% CI 13.1-18.5) in the uncontaminated area and 6.5% (95% CI 4.8-8.8) in the control population. Using a control population allowed us to differentiate baseline morbidity from the observed morbidity caused by the water contamination, thus enabling a more accurate estimate of the disease burden of this outbreak.
Laine
J
J
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Huovinen
E
E
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Virtanen
M J
MJ
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Snellman
M
M
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Lumio
J
J
Tampere University Hospital, Tampere, Finland.
Ruutu
P
P
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Kujansuu
E
E
Nokia Health Centre, Nokia, Finland.
Vuento
R
R
University of Tampere, Tampere, Finland.
Pitkänen
T
T
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Miettinen
I
I
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
Herrala
J
J
Tampere University Hospital, Tampere, Finland.
Lepistö
O
O
Environmental Health Control Unit, Pirkkala, Finland.
Antonen
J
J
Tampere University Hospital, Tampere, Finland.
Helenius
J
J
University of Tampere, Tampere, Finland.
Hänninen
M-L
ML
University of Helsinki, Helsinki, Finland.
Maunula
L
L
University of Helsinki, Helsinki, Finland.
Mustonen
J
J
Tampere University Hospital, Tampere, Finland.
Kuusi
M
M
National Institute for Health and Welfare, Helsinki and Kuopio, Finland.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D060766:Drinking Water / Q000382:microbiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000209:etiology / Q000382:microbiology; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D012722:Sewage / Q000382:microbiology*; D011795:Surveys and Questionnaires; D055815:Young Adult
D060766:Drinking Water; D012722:Sewage