Comparison of early and late latent syphilis--Colorado, 1991.

Latent syphilis (i.e., the presence of serological evidence for syphilis without clinical manifestations) is divided into early latent ([EL] less than 1-year's duration) and late latent ([LL] more than 1-year's duration) stages (1). LL syphilis, which is often associated with low nontreponemal test (e.g., rapid plasma reagin [RPR]) titers and is presumed to have been acquired in the distant past, is not routinely included in syphilis surveillance reports and analyses. Although a separate classification of "unknown latent syphilis" has been proposed (1), in practice, duration is unknown for nearly all syphilis cases that are classified as LL. This report compares EL and LL syphilis cases in Colorado during 1991 and demonstrates substantial overlap in their characteristics.