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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)

  • 21-ID-06


Chlamydia is a common sexually transmitted infection caused by the bacterium, C. trachomatis, which can be transmitted during vaginal, anal, or oral sex. About three quarters of infected women and about half of infected men have no symptoms. If symptoms occur, they usually appear within 1–3 weeks after exposure. In women, symptoms may include abnormal vaginal discharge, urethritis, lower abdominal pain, pain during intercourse, and bleeding between menstrual periods. In men, symptoms include penile discharge and urethritis. In up to 40% of untreated women, infection can spread into the uterus or fallopian tubes and cause pelvic inflammatory disease. Infected women are also up to five times more likely to become infected with HIV, if exposed. Complications among men are rare. Infection sometimes spreads to the epididymis, causing pain, fever, and, rarely, sterility.

Lymphogranuloma venereum (LGV) is a specific type of chlamydial infection caused by serovars L1–L3. LGV became nationally notifiable in 1941 but was removed from the Nationally Notifiable Conditions list as a separate notifiable condition in 1995 when chlamydia was added. However, with chlamydia being nationally notifiable and LGV being a specific type of chlamydia, as the case definition is currently written, LGV is nationally notifiable as chlamydia, but is not notifiable as a separate condition from chlamydia. It is important to distinguish between LGV and non-LGV infections in chlamydia case report data.

The language of the C. trachomatis infection case definition to include more current diagnostic technologies and to be inclusive of all possible clinical outcomes for jurisdictions to use when classifying chlamydial infections caused by LGV serovars. Allowing for the distinction between LGV and non-LGV infections in C. trachomatis infection case report data will provide us with the ability to evaluate at least the minimum burden of LGV disease in the United States.

Clinical Description

Chlamydia is a sexually transmitted infection that has a variable clinical course based on the serotype causing infection. Serovars D-K of C. trachomatis are the typical cause of chlamydial infections in the United States, and infection with C. trachomatis can result in urethritis, epididymitis, cervicitis, acute salpingitis, or other syndromes when sexually transmitted; however, the infection is often asymptomatic. Perinatal infections may result in inclusion conjunctivitis and pneumonia in newborns. Other syndromes caused by C. trachomatis include LGV and trachoma.

LGV is a specific type of chlamydial infection, caused by the serovars L1, L2, and L3 of C. trachomatis. Symptomatic LGV can be divided into three stages. The primary stage can include a small ulcer or lesion at the site of inoculation (genital, rectal, or oral/oropharyngeal sites). The secondary stage can include a syndrome featuring cervical, inguinal, and/or femoral lymphadenopathy that may rupture or an anorectal syndrome featuring proctocolitis (including mucoid or hemorrhagic rectal discharge, anal pain, constipation, fever, and/or tenesmus). Late stage LGV typically involves sequelae, such as genital elephantiasis, lymph node scarring, chronic colorectal fistulas and strictures, perirectal abscesses, and/or anal fissures. LGV may also be asymptomatic.

Laboratory Criteria

  • Demonstration of C. trachomatis in a clinical specimen by detection of antigen or nucleic acid, OR
  • Detection of LGV-specific antigen or nucleic acid in a clinical specimen, OR
  • Isolation of C. trachomatis by culture

Criteria to Distinguish a New Case from an Existing Case

For surveillance purposes, a new case of C. trachomatis infection (caused by either non-LGV or LGV serotypes) meets the following criteria:

  • There is no evidence of a prior C. trachomatis infection that has been reported as a case;


  • There is evidence of a prior C. trachomatis infection that has been reported as a case, but the prior infection’s specimen collection date or treatment date was >30 days before the current infection’s specimen collection date;


  • There is evidence of a prior C. trachomatis infection that has been reported as a case with a specimen collection date or treatment date ≤30 days from the current infection’s specimen collection date, but there is evidence of re-infection.

Case Classification


A case that meets laboratory evidence.

Case Classification Comments

The following provides guidance for health departments to use for the classification and notification of cases of C. trachomatis infection caused by serovars L1, L2, and L3 (also known as lymphogranuloma venereum, or LGV). Cases should be reported to the Centers for Disease Control and Prevention (CDC) through voluntary notification as C. trachomatis infection and should be marked as LGV in the CDC case report data, as defined below.

Classification of C. trachomatis infection cases to identify LGV.

Verified: a person with detection of LGV-specific antigen or nucleic acid in a clinical specimen. This includes asymptomatic cases.

Likely: a person with demonstration of C. trachomatis in a clinical specimen by detection of antigen or nucleic acid OR isolation of C. trachomatis by culture; AND who demonstrates clinical symptoms or signs consistent with LGV; AND has no negative test for LGV-specific antigen or nucleic acid in a clinical specimen.

Related Case Definition(s)