Epidemiology

Chancroid was endemic worldwide until the 20th century, but is now most common in the Caribbean, Africa, Asia (except Thailand), and Latin America. There were an estimated 7 million new cases in the world during 1995; however, due to difficulties in diagnosis and reporting, the true number is unknown.[10][11]

The prevalence of chancroid has significantly declined in some countries, which is thought to be due to the therapeutic syndromic management of genital ulcer disease and significant social change.[9] In the US, the prevalence peaked in 1947 with over 9500 cases and has since declined dramatically.[12]​ In 2023, only four cases of chancroid were reported in the US. However, data informing national trends should be interpreted with caution as Haemophilus ducreyi infections may be underdiagnosed in areas where diagnostic capacity with culture is limited or not undertaken.[13]​​

Periodic spikes in chancroid incidence have been attributed to a concurrent increase in the number of syphilis cases, use of cocaine, and exchange of sex for drugs.[2][14]​ Studies have shown that the minimum number of partners to maintain chancroid in a population is 15 to 20 per year.[11] The exact rate of transmission per sexual act is thought to be high but is not known. The probability of transmission from a single exposure has been estimated to be 0.35.[15]

In Thailand, a 100% condom use policy and presumptive treatment of sex workers in commercial sex establishments has been very effective; no cases of chancroid have been reported since 1998. In Africa, where rates of circumcision are low and incidence of HIV is high, chancroid remains endemic. The prevalence is lower in countries with a higher use of condoms (e.g., Kenya), and with regular examination and treatment of sex workers. Syndromic treatment of genital ulcer disease (simultaneous treatment of all potential co-infections) has been implemented in several regions, such as Senegal and India, successfully reducing the incidence.[11][16]

The male to female ratio of infection is 3:1 in endemic areas and 25:1 in outbreaks in developed countries. Asymptomatic carriage is thought to be rare.[17]

H ducreyi has also been described as a cause of non-sexually transmitted cutaneous skin ulcers in the South Pacific and Africa. Epidemiological surveys to evaluate yaws elimination programmes in yaws-endemic areas have revealed H ducreyi to be an aetiological agent of limb ulcers.[3][4][5][6][7][8][9][18]​​ Studies in both Papua New Guinea and Cameroon have found H ducreyi DNA on the skin of asymptomatic children, in flies, and on fomites.[19][20]​​ The ubiquitous nature of H ducreyi in endemic regions warrants further evaluation.[18][19]​​​​ Strains of H ducreyi isolated from cutaneous ulcerations have genome sequences similar to clade I and clade II strains of H ducreyi, which cause genital ulcerations.[7]​​[18][21]​​[22]

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