06. tbl. 106. árg. 2020

Waterborne outbreaks in Iceland - analysis of scale and causes

Vatnsbornar hópsýkingar á Íslandi – greining á umfangi og ástæðum

Purpose: Clean drinking water is essential for public health. The cause of waterborne outbreaks is most often fecal contamination of water from animals or humans. The objective of this resarch was to collect available information on waterborne outbreaks in Iceland for a twenty year period, 1998-2017. Incident of fecal and pathogenic pollution in samples where also collected although rarely followed by registered outbreak.

Methods: Data are obtained from laboratory databases, the Office of the Director of Health, reports and interviews with the relevant surveillance authorities and epidemiologists.

Results: The results show that for the period investigated there have been registered fifteen waterborne outbreaks, all in small water supplies though many are serving also transitent population, tourists and summerhouse dwellers. About 500 illnesses were confirmed and affected about 8000 people. Other research have shown that around 10% of illnesses in waterborne outbreaks are registered so it can be estimated that on average 250 people have been taken ill every year because of contaminated drinking water. Analysis of monitoring water quality data show that on average 50 water supplies have fecal incident each year which is 5% of the Icelandic regulated water supplies. The most frequent cause of waterborne outbreak was a bad design and maintainance of water intakes.

Conclusions: It is likely that waterborne outbreaks are more numerous than are registered in official reports and especially in small water supplies. It also seems that the local heath authorities are often not informed of incidents of non-compliance. It is important to improve registration, information exchange between parties, epidemiological surveys and follow up of outbreaks due to drinking water to gather lessons learned. Water quality at small water supplies needs to be improved with risk-based approach and risk management.

Key words: Waterborne outbreaks, drinking water, drinking water quality, small water supplies.

Figure 1. Monthly distribution of waterborne disease outbreaks and boil advisories 1998-2017 (each incident is register in the month it begins).

Figure 2. Number of drinking water samples tested for Campylobacter at the jurisdiction of each Local Competent Authority in the period 1998-2014.

Figure 3. Number of samples and water supplies where E. coli was identified in the period 1998-2014.

Figure 4. Causes of waterborne outbreaks and boil advisories.

Table I. Registered waterborne disease outbreaks in Iceland 1998-2017.

Table II. Boil advisories at water supplies in the period 1998-2017.

Table III. Search for pathogens in drinking water 1998-2017.

Table IV. Water supplies tested positive for Campylobacter in drinking water samples 1998-2017.

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