Q Fever: Single-Point Source Outbreak With High Attack Rates and Massive Numbers of Undetected Infections Across an Entire Region

Background. In early 2009, a dairy-goat annex care farm in South Limburg, the Netherlands, reported 220 Coxiella burnetii-vehted abortions in 450 pregnant goats. These preceded human cases and occurred in a region that was Q-fever free before 2009, providing a unique quasi-experimental setting for i...

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Bibliographic Details
Published in:Clinical infectious diseases 2012-12, Vol.55 (12), p.1591-1599
Main Authors: Hackert, Volker H., van der Hoek, Wim, Dukers-Muijrers, Nicole, de Bruin, Arnout, Dahouk, Sascha Al, Neubauer, Heinrich, Bruggeman, Cathrien A., Hoebe, Christian J. P. A.
Format: Article
Language:English
Subjects:
Adult
Aged
Agricultural population
Agriculture
Animals
Antibodies, Bacterial - blood
ARTICLES AND COMMENTARIES
Bacterial diseases
Biological and medical sciences
Contact Tracing
Coxiella burnetii
Coxiella burnetii - isolation & purification
Disease Outbreaks - veterinary
Disease transmission
Epidemics
Female
General practice
Goat Diseases - epidemiology
Goat Diseases - microbiology
Goats
Health risk assessment
Human bacterial diseases
Humans
Immunoglobulins
Incidence
Infections
Infectious diseases
Male
Medical sciences
Middle Aged
Netherlands - epidemiology
Pregnancy
Public health
Q fever
Q Fever - epidemiology
Q Fever - veterinary
Retirement communities
Rickettsial diseases
Seroepidemiologic studies
Sheep
Sheep Diseases - epidemiology
Sheep Diseases - microbiology
Tropical bacterial diseases
Zoonoses - epidemiology
Zoonoses - microbiology
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Summary:Background. In early 2009, a dairy-goat annex care farm in South Limburg, the Netherlands, reported 220 Coxiella burnetii-vehted abortions in 450 pregnant goats. These preceded human cases and occurred in a region that was Q-fever free before 2009, providing a unique quasi-experimental setting for investigating regional transmission patterns associated with a Q-fever point source. Methods. Index-farm residents/employees, visitors, and their household contacts were traced and screened for C. burnetii. Distribution of community cases was analysed using a geographic information system. True incidence, including undetected infections, was estimated regionwide by seroprevalence in a pre-versus postoutbreak sample, and near-farm by immunoglobulin M seroprevalence in a municipal population sample. Environmental bacterial load was repeatedly measured in surface and aerosol samples. Results. Serological attack rate was 92% (24/26) in index-farm residents/employees, 56% (28/50) in visitors, and 50% (7/14) in household contacts, and the clinical attack rate (ie, the proportion of persons seropositive for acute infection who also had clinical illness) was ≥80%. Notified symptomatic community cases (n = 253) were scattered downwind from the index farm, following a significant exposure-response gradient. Observed incidence ranged from 6.3% (0–1 km) to 0.1% (4–5 km), and remained high beyond. True incidence of infections was estimated at 2.9% regionwide, extrapolating to 8941 infections; estimated near-farm incidence was 12%. Coxiella burnetii load was high on-farm (2009), and lower off-farm (2009-2010). Conclusions. Linking a single dairy-goat farm to a human Q-fever cluster, we show widespread transmission, massive numbers of undetected infections, and high attack rates on-and off-farm, even beyond a 5-km high-risk zone. Our investigation may serve as an essential case study for risk assessment in public health and related fields such as bioterrorism response and preparedness.
ISSN:1058-4838
1537-6591
DOI:10.1093/cid/cis734