Volume 17, Number 12—December 2011
Q Fever in Woolsorters, Belgium
|Serologic status||ELISA† (years 1–3)||IFA‡ (year 3)||Confirmed§ (years 1–3)|
|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|
*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.