An extensive gastroenteritis outbreak after drinking-water contamination by sewage effluent, Finland

Area of Science:

• Environmental health
• Epidemiology
• Public health

Background:

• A Finnish town experienced a significant waterborne gastroenteritis outbreak due to a sewage and drinking water pipeline cross-connection.
• The initial investigation identified 1,222 individuals seeking medical care and seven pathogens in patient samples.

Purpose of the Study:

• To accurately estimate the total disease burden of the waterborne gastroenteritis outbreak.
• To differentiate outbreak-related illnesses from baseline morbidity using a control population.

Main Methods:

• Conducted a population-based questionnaire investigation across contaminated, uncontaminated, and control town areas.
• Utilized a control population, a less common method for studying waterborne outbreaks, to establish baseline illness rates.

Main Results:

• An estimated 8,453 residents fell ill, with an excess of 6,501 illnesses attributed to the outbreak.
• Attack rates were 53% in the contaminated area, 15.6% in the uncontaminated area, and 6.5% in the control population.

Conclusions:

• The study provided a more accurate disease burden estimate by accounting for baseline morbidity.
• The findings underscore the critical need for robust water infrastructure to prevent such public health emergencies.