Elfatih Yousif, YousifAltaj Altayeb, AltayebAbdul-Aziz, RehabSalahaldeen, IsmailMohamed Elkhidir, Isam2017-09-122017-09-122017-06-01http://hdl.handle.net/123456789/5136Background: The differentiation between fresh and long -standing infections is one of the greatest challenges in serology. Until now this was based mainly on determination of specific antibodies of the immunoglobulin class IgM,which generally only appear initially