NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.
CSTE Position Statement(s)
Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. Syphilis is passed from person to person through direct contact with a syphilitic chancre. Chancres occur mainly on the external genitals, vagina, anus, or in the rectum, but can also occur on the lips and in the mouth. Transmission of the organism occurs during vaginal, anal, or oral sex. Pregnant women with the disease can transmit it through the placenta to the fetus or at birth to the neonate. Many people infected with syphilis do not have any symptoms for years, yet remain at risk for late complications if they are not treated. Although transmission occurs from persons with chancres who are in the primary or secondary stage, many of these chancres are unrecognized. Thus, transmission may occur from persons who are unaware of their infection.
In the United States, testing for syphilis traditionally has consisted of initial screening with an inexpensive nontreponemal test, followed by retesting reactive specimens with a more specific treponemal test. Nontreponemal tests, such as the Rapid Plasma Reagin (RPR) test and Venereal Disease Research Laboratory (VDRL) test, detect antibodies to cardiolipin and are not specific for treponemal infection. Nontreponemal tests are more likely than treponemal tests to produce nonreactive results after treatment; therefore, reactive results from nontreponemal tests are more reliable indicators of untreated infection. Quantitative nontreponemal tests are also used to monitor responses to treatment or to indicate new infections.
Treponemal tests detect antibodies specific to Treponema pallidum. In addition to Treponema pallidum, which causes syphilis, other treponemal subspecies (e.g., pertenue, which causes yaws, and carateum, which causes pinta) also can produce reactive results to treponemal tests, but these subspecies are rare in the United States. A reactive treponemal test result indicates that treponemal infection has occurred at some point in the past but cannot distinguish between treated and untreated infections. As such, treponemal tests can produce reactive results for life, even after adequate treatment for syphilis. Both treponemal and nontreponemal tests can produce nonreactive results when the infection has been acquired recently; approximately 20% of test results are negative when patients have primary syphilis.
In the last five years, there has been an increase in the adoption of automated treponemal tests by laboratories which has resulted in the syphilis testing algorithm being reversed. Many laboratories now use an automated treponemal test as the initial screening test followed by a nontreponemal test. While this algorithm is more time and cost effective for laboratories, it does have a ~14-40% false-positive rate, with a second treponemal test often being used to help determine what clinical action should be taken. In addition to this change, polymerase chain reaction tests for syphilis can be performed by clinical laboratories that have developed their own tests and have conducted verification studies in accordance with the Clinical Laboratories Improvement Amendment (CLIA).
Although men who have sex with men currently account for the majority of infectious syphilis cases in the United States, syphilis among women and congenital syphilis continue to be a problem. In 2012, there were 322 cases of congenital syphilis reported. The reporting form and case investigation procedures for congenital syphilis cases were also updated in 2013.
A condition caused by infection in utero with Treponema pallidum. A wide spectrum of severity exists, from inapparent infection to severe cases that are clinically apparent at birth. An infant or child (aged less than 2 years) may have signs such as hepatosplenomegaly, rash, condyloma lata, snuffles, jaundice (nonviral hepatitis), pseudoparalysis, anemia, or edema (nephrotic syndrome and/or malnutrition). An older child may have stigmata (e.g., interstitial keratitis, nerve deafness, anterior bowing of shins, frontal bossing, mulberry molars, Hutchinson teeth, saddle nose, rhagades, or Clutton joints).
Laboratory Criteria for Diagnosis
Demonstration of Treponema pallidum by:
- Darkfield microscopy of lesions, body fluids, or neonatal nasal discharge, or
- Polymerase chain reaction (PCR) or other equivalent direct molecular methods of lesions, neonatal nasal discharge, placenta, umbilical cord, or autopsy material, or
- Immunohistochemistry (IHC), or special stains (e.g., silver staining) of specimens from lesions, placenta, umbilical cord, or autopsy material.
A condition affecting an infant whose mother had untreated or inadequately treated* syphilis at delivery, regardless of signs in the infant, or an infant or child who has a reactive non-treponemal test for syphilis (Venereal Disease Research Laboratory [VDRL], rapid plasma reagin [RPR], or equivalent serologic methods) AND any one of the following:
- Any evidence of congenital syphilis on physical examination (see Clinical description)
- Any evidence of congenital syphilis on radiographs of long bones
- A reactive cerebrospinal fluid (CSF) venereal disease research laboratory test (VDRL) test
- In a nontraumatic lumbar puncture, an elevated CSF leukocyte (white blood cell, WBC) count or protein (without other cause):
Suggested parameters for abnormal CSF WBC and protein values:
- During the first 30 days of life, a CSF WBC count of >15 WBC/mm3 or a CSF protein >120 mg/dL.
- After the first 30 days of life, a CSF WBC count of >5 WBC/mm3 or a CSF protein >40 mg/dL, regardless of CSF serology.
The treating clinician should be consulted to interpret the CSF values for the specific patient.
Syphilitic stillbirth: A fetal death that occurs after a 20-week gestation or in which the fetus weighs greater than 500 g and the mother had untreated or inadequately treated* syphilis at delivery.
*Adequate treatment is defined as completion of a penicillin-based regimen, in accordance with CDC treatment guidelines, appropriate for stage of infection, initiated 30 or more days before delivery.
A case that is laboratory confirmed.
Congenital and acquired syphilis may be difficult to distinguish when a child is seropositive after infancy. Signs of congenital syphilis may not be obvious, and stigmata may not yet have developed. Abnormal values for CSF VDRL, WBC count, and protein may be found in either congenital or acquired syphilis. Findings on radiographs of long bones may help because radiographic changes in the metaphysis and epiphysis are considered classic signs of congenitally acquired syphilis. While maternal antibodies can complicate interpretation of serologic tests in an infant, reactive tests past 18 months of age are considered to reflect the status of the child. The decision may ultimately be based on maternal history and clinical judgment. In a young child, the possibility of sexual abuse should be considered as a cause of acquired rather than congenital syphilis, depending on the clinical picture. For reporting purposes, congenital syphilis includes cases of congenitally acquired syphilis among infants and children as well as syphilitic stillbirths.
The 1996 and 1990 syphilis case definitions include the case definition for congenital syphilis.