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Volume 17, Number 12—December 2011


Q Fever in Woolsorters, Belgium

Pierre WattiauComments to Author , Eva Boldisova, Rudolf Toman, Marjan Van Esbroeck, Sophie Quoilin, Samia Hammadi, Hervé Tissot-Dupont, Didier Raoult, Jean-Marie Henkinbrant, Mieke Van Hessche, and David Fretin
Author affiliations: Veterinary and Agrochemical Research Centre, Brussels, Belgium (P. Wattiau, M. Van Hessche, D. Fretin); Slovak Academy of Sciences, Bratislava, Slovakia (E. Boldisova, R. Toman); Institute of Tropical Medicine, Antwerp, Belgium (M. Van Esbroeck); Institute of Public Health, Brussels (S. Quoilin, S. Hammadi); Université de la Méditerranée, Marseille, France (H. Tissot-Dupont, D. Raoult); Occupational Health Medicine Group Provikmo, Verviers, Belgium (J.-M. Henkinbrant)

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Serologic results for Q fever in woolsorters, Belgium, 2007–2009*

Serologic status ELISA† (years 1–3) IFA‡ (year 3) Confirmed§ (years 1–3)
No. negative 29 27 34
No. nonspecifically reactive NA 9 NA
No. with past infection 31 31 26
No. with recent or active infection 7 NA 8
No. with chronic infection 2 2 1
% Seroreactive 57.9 47.8 50.7

*IFA, immunofluorescent assay; NA, not applicable.
†Conducted on samples collected annually for 3 y. Serologic titer for chronic Q fever: phase I IgG >12,800 and > phase II IgG; for recent or active infection, phase II IgG >1,600 and phase II IgM >800; for past infections, phase II IgG >1,600 and phase II IgM <800.
‡Conducted on paired samples in cases of suspected or noninterpretable initial results; conducted on single samples in all other cases. Serologic status was defined at year 3 according to the instructions of the test kit manufacturer (Focus Diagnostics, Cypress, CA, USA).
§Workers with test results above the threshold at least once over a 3-y period by ELISA and IFA. Serologic status was adjusted on the basis of the 3-y projection and retesting in the reference laboratory in France.

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