Syphilis, early non-primary non-secondary
2026 Case Definition

Background

A stage of infection with T. pallidum characterized by no clinical signs or symptoms of primary or secondary syphilis and evidence that the infection occurred during the previous 12 months.

Clinical Criteria

• Documented history of syphilis.

Laboratory Criteria

Confirmatory Laboratory Evidence:

• Direct detection of T. pallidum by nucleic acid amplification test (e.g., PCR, LAMP) or a diagnostically equivalent molecular method in any specimen.

Presumptive Laboratory Evidence:

• A current (i.e., a test performed in the context of this index presentation) reactive blood-based nontreponemal antibody test (i.e., VDRL, RPR, point-of-care, or equivalent nontreponemal method), AND
• A reactive blood-based treponemal antibody test (i.e., TP-PA, EIA, CIA, MFI or MIA, FTA-ABS, point-of-care, or equivalent treponemal method)^¶.

Supportive Laboratory Evidence:

• A current (i.e., a test performed in the context of this index presentation) blood-based nontreponemal antibody test titer demonstrating a fourfold or greater increase,^** AND
• No evidence of a concurrent nonreactive blood-based treponemal antibody test.

Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.

^¶Current or historical reactive treponemal antibody tests can be used to satisfy this criterion.

^**For surveillance purposes, the blood-based nontreponemal antibody test is not required to be repeated. However, in the absence of treatment initiation, when blood-based nontreponemal antibody testing is repeated, if the repeat specimen is collected less than or equal to 30 days after the specimen that demonstrated a fourfold increase in titers, and the repeat specimen demonstrates that the fourfold increase in titers was not sustained, the case does not meet the supportive laboratory evidence for early non-primary non-secondary syphilis.

Epidemiologic Linkage

• Sexual exposure to a partner during the previous 12 months who had primary, secondary, or early non-primary non-secondary syphilis (documented independently as duration of syphilitic infection less than or equal to 12 months), OR
• Only sexual contact (sexual debut) was during the previous 12 months.

Other Evidence of Infection Acquired during Previous 12 Months

• Does not meet clinical criteria AND has evidence of seroconversion of a blood-based nontreponemal antibody or treponemal antibody test in a specimen that was collected during the previous 12 months, OR
• Meets clinical criteria AND has evidence of a current (i.e., a test performed in the context of this index presentation) blood-based nontreponemal antibody test titer demonstrating a fourfold or greater increase in a specimen that was collected during the previous 12 months, OR
• Signs or symptoms consistent with primary or secondary syphilis during the previous 12 months, OR
• Greater than or equal to fourfold increase in a blood-based nontreponemal antibody test titer from a specimen that was collected between the initial specimen collection date and the treatment initiation date.

Probable

• Does not meet clinical criteria AND meets presumptive laboratory evidence AND meets epidemiologic linkage criteria, OR
• Does not meet clinical criteria AND meets presumptive laboratory evidence AND meets other evidence of infection acquired during previous 12 months, OR
• Meets clinical criteria AND meets supportive laboratory evidence AND meets epidemiologic linkage criteria, OR
• Meets clinical criteria AND meets supportive laboratory evidence AND meets other evidence of infection acquired during previous 12 months.

Confirmed

• Meets confirmatory laboratory evidence AND meets epidemiologic linkage criteria, OR
• Meets confirmatory laboratory evidence AND meets other evidence of infection acquired during previous 12 months.

• Syphilis (Treponema pallidum) | 2026 Case Definition