Abstract
BackgroundIn 2010–2011, two large waterborne outbreaks caused by Cryptosporidium hominis affected two cities in Sweden, Östersund and Skellefteå. We investigated potential post-infection health consequences in people who had reported symptoms compatible with cryptosporidiosis during the outbreaks using questionnaires.MethodsWe compared cases linked to these outbreaks with non-cases in terms of symptoms present up to eleven months after the initial infection. We examined if cases were more likely to report a list of symptoms at follow-up than non-cases, calculating odds ratios (OR) and 95 % confidence intervals (CI) obtained through logistic regression.ResultsA total of 872 (310 cases) and 743 (149 cases) individuals responded to the follow-up questionnaires in Östersund and Skellefteå respectively. Outbreak cases were more likely to report diarrhea (Östersund OR: 3.3, CI: 2.0-5.3. Skellefteå OR: 3.6, CI: 2.0-6.6), watery diarrhea (Östersund OR: 3.4, CI: 1.9-6.3. Skellefteå OR: 2.8, CI: 1.5-5.1) abdominal pain (Östersund OR: 2.1, CI: 1.4-3.3, Skellefteå OR: 2.7, CI: 1.5-4.6) and joint pain (Östersund OR: 2.0, CI: 1.2-3.3, Skellefteå OR: 2.0, CI: 1.1-3.6) at follow-up compared to non-cases.ConclusionsOur findings suggest that gastrointestinal- and joint symptoms can persist several months after the initial infection with Cryptosporidium and should be regarded as a potential cause of unexplained symptoms in people who have suffered from the infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-1871-6) contains supplementary material, which is available to authorized users.
Highlights
In 2010–2011, two large waterborne outbreaks caused by Cryptosporidium hominis affected two cities in Sweden, Östersund and Skellefteå
We examined symptoms at follow-up associated to outbreak case status by calculating odds ratios (OR) and 95 % confidence intervals (CI) obtained through logistic regression [17]
Non-response analysis We examined if sex, age, dwelling-place and case status of the study population were associated with nonresponse by calculating OR and 95 % CI using logistic regression modeling
Summary
In 2010–2011, two large waterborne outbreaks caused by Cryptosporidium hominis affected two cities in Sweden, Östersund and Skellefteå. We investigated potential post-infection health consequences in people who had reported symptoms compatible with cryptosporidiosis during the outbreaks using questionnaires. Cryptosporidium is a protozoan parasite that can cause gastrointestinal illness in humans and animals [1, 2]. Several species of the parasite have been identified. Cryptosporidium parvum and C. hominis are the most prevalent species in humans. Cryptosporidiosis is transmitted mainly by the fecal-oral route, mostly by oocyst-contaminated water or food, or by direct contact with an infected person or animal [3]. Cryptosporidiosis occurs worldwide, and in all age groups [1], children especially during the first year of life are frequently and severely affected [2, 4].
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