Research article

Investigation of Swedish cases reveals an outbreak of cryptosporidiosis at a Norwegian hotel with possible links to in-house water systems

Agnes Hajdu^1,2 , Line Vold¹ , Torild A Østmo³ , Anna Helleve³ , Sigrid R Helgebostad⁴ , Truls Krogh⁵ , Lucy Robertson⁶ , Birgitta de Jong⁷ and Karin Nygård¹

¹Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health, Oslo, Norway

²European Programme for Intervention Epidemiology Training (EPIET), Swedish Institute for Infectious Disease Control, Solna, Sweden

³District Office for Asker and Bærum, Norwegian Food Safety Authority, Sandvika, Norway

⁴Municipal Health Authority, Asker, Norway

⁵Department of Water Hygiene, Norwegian Institute of Public Health, Oslo, Norway

⁶Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway

⁷Department of Communicable Disease Control and Prevention, Stockholm County Council, Stockholm, Sweden

author email corresponding author email

BMC Infectious Diseases 2008, 8:152doi:10.1186/1471-2334-8-152

Published:	1 November 2008

Abstract

Background

In March 2007, the Norwegian Institute of Public Health was notified of Swedish individuals diagnosed with cryptosporidiosis after staying at a Norwegian hotel. In Norway, cryptosporidiosis is not reportable, and human infections are rarely diagnosed.

Methods

A questionnaire on illness and exposure history was e-mailed to seven organised groups who had visited the hotel in March. Cases were defined as persons with diarrhoea for more than two days or laboratory-confirmed cryptosporidiosis during or within two weeks of the hotel visit. The risk factor analysis was restricted to two groups with the highest attack rates (AR) and same hotel stay period. Local food safety authorities conducted environmental investigations.

Results

In total, 25 diarrhoeal cases (10 laboratory-confirmed) were identified among 89 respondents. Although environmental samples were negative, epidemiological data suggest an association with in-house water consumption. In one group, the AR was higher amongst consumers of water from hotel dispenser (relative risk [RR] = 3.0; 95% confidence interval [CI]: 0.9–9.8), tap water (RR = 2.3; CI: 0.9–5.8), and lower amongst commercial bottled water drinkers (RR = 0.6; CI: 0.4–1.0). Consumption of ice cubes was a risk-factor (RR = 7.1; CI: 1.1–45.7) in the two groups combined.

Conclusion

This outbreak would probably have remained undetected without the alert from Swedish health authorities, illustrating the difficulties in outbreak detection due to low health care seeking behaviour for diarrhoea and limited parasite diagnostics in Norway. Awareness of cryptosporidiosis should be raised amongst Norwegian medical personnel to improve case and outbreak detection, and possible risks related to in-house water systems should be assessed.