Volume 17, Number 12—December 2011
Letter
Q Fever in Woolsorters, Belgium
Table
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.