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Epidemiologic Notes and Reports Chancroid -- California

From May 1, 1981, to March 19, 1982, 389 patients with dark-field-negative genital ulcers were seen in the Orange County (California) Special Diseases Clinic (OCSDC). Haemophilus ducreyi was identified as the causative organism in this outbreak on December 28, 1981. Since then, cultures from genital lesions obtained from 126 patients have grown H. ducreyi. The outbreak of chancroid began in late May 1981 when the number of patients with dark-field-negative genital lesions seen at the OCSDC increased markedly. The peak number of H. ducreyi-positive cultures occurred in the week ending January 16, 1982 (Figure 1). Although primary and secondary syphilis and genital herpes infections have been hyperendemic in Orange County, chancroid has never before been documented there at such high levels.

Ninety-one percent of the patients were Hispanic men, many of whom were recent immigrants from Mexico currently living in central Orange County in crowded apartments (5-15 occupants per single housing unit). At least 77% of these men had had recent sexual contact with prostitutes. Examination of 2 prostitutes from that area, who presumably had multiple contacts with male chancroid patients but for whom no direct contact could be established, showed no lesions. However, when cultures of the cervix, urethra, and vagina were done, H. ducreyi was recovered from cervical specimens from both women.

Ninety-five percent of the confirmed or presumptive cases* were in men with genital ulcers (ranging from 0.3 cm to 2.5 cm in diameter) and/or enlarged inguinal nodes. The lesions were single or multiple, superficial or deep, sometimes indurated, and often with ragged edges and a purulent base. Tender, unilateral or bilateral inguinal nodes were present in 32% of patients, and in some patients these progressed to the formation of fluctuant buboes.

Dark-field and serologic tests for syphilis, cultures for Herpes simplex virus (HSV), and serologic tests for chlamydiae (for diagnosis of lymphogranuloma venereum) have been negative in nearly all instances. However, 2 patients had lesions that were positive for syphilis (Treponema pallidum was identified on dark-field examination) and for H. ducreyi simultaneously, and 1 patient had a lesion that yielded HSV as well as H. ducreyi. In addition, 2 cases of culture-proven chancroid were identified in 1 week at the OCSDC for patients whose lesions were described as "typical herpes," although HSV was not isolated.

Antimicrobial susceptibility tests performed at CDC on 29 isolates of H. ducreyi from this outbreak showed resistance to sulfamethoxazole and tetracycline but susceptibility to erythromycin--mean minimum inhibitory concentration (MIC) of less than or equal to 0.004 ug/ml--and to trimethoprim/sulfamethoxazole--mean MIC less than or equal to 0.06/1.2 ug/ml. Reported by JR Greenwood, PhD, T Prendergast, MD, LR Ehling, MD, Orange County Health Dept, C Zavala, J Chin, MD, State Epidemiologist, California Dept of Health; Sexually Transmitted Diseases Laboratory Program, Center for Infectious Diseases, Field Svcs Div, Epidemiology Program Office, Venereal Disease Control Div, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Chancroid is a sexually transmitted disease that is rarely reported in temperate climates and may be confused with primary syphilis and genital herpes infections. The mean number of cases reported annually in the United States and California from 1974 to 1980 was 697 and 29, respectively (1,2).

H. ducreyi is a fastidious, gram-negative bacterium that is difficult to grow in vitro, and may not be detected unless careful collection and isolation techniques are employed. The bacterium requires high humidity and a slightly lower temperature for growth (33 -35 C) than do other bacteria (35 -37 C). Also many strains show variation in nutritional requirements. To obtain optimal recovery, several types of plating media should be used for each culture. The Orange County Public Health Laboratory has achieved the greatest rate of recovery by using enriched chocolate agar, but some strains grow only on Heart Infusion agar supplemented with 10% fetal bovine serum (3). Microbiologists may contact the CDC Sexually Transmitted Disease Research Laboratory for additional information on the isolation of H. ducreyi.

Considerable variation occurs in antibiotic susceptiblity patterns for H. ducreyi, making obsolete the treatment suggested in most medical textbooks. Resistance of this organism to sulfamethoxazole alone and to tetracycline has been noted in recent years (4,5). CDC currently recommends 500 mg erythromycin by mouth 4 times a day for 10 days as the treatment of choice for chancroid. An alternative effective regimen is 800 mg sulfamethoxazole and 160 mg trimethoprim by mouth 2 times a day for 10 days. Recent laboratory testing has shown H. ducreyi to be very sensitive to several newer cephalosporin drugs. Research is needed to determine if a single dose of a cephalosporin with a long biologic half-life would be more effective treatment.

Follow-up evaluations should be at no more than 1-week intervals and should continue until the lesions are completely resolved. To prevent transmission of this infection, patients must abstain from sexual activity while clinical disease is present and, because asymptomatic carriage of the organisms is possible, recent sexual partners of patients must be treated with a regimen adequate for uncomplicated chancroid. When chancroid is left untreated, the patient often develops an inguinal bubo that may spontaneously rupture. Necrotic ulcers and erosive lesions that destroy genital tissue have also been reported.

Control strategies in the Orange County outbreak have focused on interviewing persons with confirmed cases for names of sexual partners; this has not successfully identified new cases. During a door-to-door educational campaign in 10 high-risk neighborhoods, no new cases were found. Intensified efforts have been implemented to identify and treat prostitutes.

This outbreak of chancroid is not yet controlled and could spread to other areas, emphasizing the need for prompt diagnosis, treatment, and epidemiologic investigation. Because this disease is uncommon in the United States, current surveillance measures may not be sufficient to detect similar outbreaks should they occur. All sexually-transmitted-disease clinics, private physicians, and other health-care providers should report cases of presumed chancroid to their county or state health departments. The forwarding of isolates of H. ducreyi to CDC should be coordinated with state laboratories.


  1. Sexually Transmitted Disease (STD) Statistical Letter, U.S. Department of Health and Human Services, #129, 1979.

  2. Venereal Disease Control Division, Center for Prevention Services, CDC, 1982.

  3. California Department of Health Services. An outbreak of chancroid in Orange County. California Morbidity 1982, February 12:5.

  4. Albritton WL, Brunton JL, Slaney L, MacLean I. Plasmid-mediated sulfonamide resistance in Haemophilus ducreyi. Antimicrob Agents Chemother 1982;21:159-65.

  5. Handsfield HH, Totten PA, Fennel CL, Falkow S, Holmes KK. Molecular epidemiology of Haemophilus ducreyi infections. Ann Intern Med 1981;95:315-8. *A confirmed case of chancroid was defined by the recovery of H. ducreyi from a culture of the genital lesion. A presumptive or suspected case of chancroid was defined by the absence of a positive culture for H. ducreyi and of any clinical diagnosis other than chancroid, such as a traumatic tear or folliculitis, plus any of the following:

    1. A genital ulcer

      1. negative upon dark-field examination

      2. with accompanying negative serologic test for syphilis (STS)

      3. with no mention of genital herpes in the history, no diagnosis of herpes for this lesion after repeated visits, or no positive culture for Herpes simplex virus; or

    2. A grossly enlarged, fluctuant, or aspirated inguinal node or bubo in a patient with negative STS results; or

    3. A genital ulcer that has not healed after appropriate syphilis treatment, regardless of STS results.

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