Specific risk factors for contracting Q fever: Lessons from the outbreak Jena

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Abstract

A Q fever outbreak with 331 reported cases in seven weeks occurred in a densely populated residential district in Jena (Germany) in 2005. Prompt identification of a stable infection source follow by an intense information policy, well defined and stable meteorological conditions and a large number of reported cases within one small community all allowed us to study promoting and protecting factors of Q fever. We conducted a cross-sectional study and investigated a part of the affected area for 100% sampling (in-home interviews).

Out of 608 residents at home 460 (75.7%) participated in the study and 101 fulfilled our definition of an acute Q fever case.

Our data revealed a critical zone for residency within 500 m of herds of gestating ewes in a typical urban dwelling area. We found an association between shift work and contracting Q fever. An association between outdoor activity and Q fever was only found after prolonged outdoor stays, on average more than 4 h/day. Only open windows facing the putative source were associated with increased risk of Q fever. Therefore fully open windows of more than 6 h/day is a significant parameter.

Section snippets

Methods

We performed a cross-sectional study of demographic and behavioural factors associated with Q fever disease. We investigated a section of the affected area for 100% sampling. This particular area contained rows of remarkably similar buildings all with balconies facing the source area at approximately the same angle (Fig. 1). All registered occupants (n = 875) were mailed a participation request and given the dates. The in-home interviews were conducted by trained interviewers (students) using a

Results

The registration office Jena provided data from 867 occupants. Of these, 608 were at home. 460 (75.7%) participated in the study and 148 refused participation.

In total we detected 101 cases among the 460 participants. Of these 101 cases 44 fulfilled our criteria of fever combined with symptoms without performance of an antibody testing. Seven tested positive for C. burnetii specific antibodies corresponding to a recent infection without symptoms and 50 fell in both categories, clinical symptoms

Discussion

Our study describes risk factors for getting Q fever in an urban outbreak under typical summer weather conditions. The mean air temperature was with 17.2 °C (0.5 K, min. 5.1 °C, max. 32.2 °C) in the normal range. But there was a dry period of 5 days at the end of lambing. Most of significant outbreaks are preceded by a period of dry weather like in our situation (Lyytikainen et al., 1997, Karagiannis et al., 2009). Furthermore outbreaks are often attributed to windborne spread, frequently during

Funding

This work was supported by the Federal Ministry of Education and Research Germany (Grant 01 KI 0735 and 01 KI 1001C).

Acknowledgment

We thank Ivonne Riethmüller for her significant contribution to the field work.

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