serotyping ELISAs using subgroup- and serotype-
specific monoclonal antibodies (mAb) as
described previously (Greenberg et al., 1983 ; Ciarlet
et al., 1994a, 1996). Nineteen out of the 20 samples
were determined to be subgroup 1, while one
reacted with both subgroup-specific mAbs 255160
(subgroup I) and 631/9 (subgroup II) (data not
shown), kindly provided by H.B. Greenberg (Stan-