Association between syphilis seroprevalence and age among blood donors in Southern China: an observational study from 2014 to 2017

Wu, Xiaobing; Guan, Yang; Ye, Jianbin; Fu, Hanlin; Zhang, Chunlai; Lan, Lina; Wu, Fengxin; Tang, Fen; Wang, Feng; Cai, Yumao; Yu, Weiye; Feng, Tiejian

years. 2 Chronic non-communicable diseases, including cardiovascular disease, malignant neoplasms, and chronic respiratory diseases, are the leading contributors to disease burden in older people. 2 However, infectious diseases also considerably affect older people, as an increasing incidence of infectious diseases, such as human immunodeficiency virus (HIV) and syphilis, was shown from recent surveillance data. [3] [4] [5] This large disease burden among older people calls for improvements in the healthcare system and more investments and programs focusing on healthy ageing. 2 Syphilis, caused by Treponema pallidum, is a chronic infection with diverse clinical manifestations occurring in distinct stages, and may lead to blindness, dementia, delirium, death, etc., if not treated immediately or adequately. 6 Syphilis can also aid the passage for HIV to invade, reduce the CD4 T-cell levels, and increase the viral load, thereby aggravating the harm caused by HIV. 7 Even though syphilis can be effectively treated with penicillin, about 36.4 million new cases occur annually. 8 In China, the syphilis epidemic has rapidly increased, with 16.3% increase per year during the first decade after the severe acute respiratory syndrome (SARS) outbreak. 9 The reported incidence was slightly higher among females than males (ratio, 1.00 to 0.92), but it varied significantly with age. 5 Younger people (aged 20-39 years) reported the highest syphilis incidence and accounted for the largest proportion of newly reported cases; however, the older age groups (aged ≥45 years) had the fastest growth in incidence, and males aged ≥60 years displayed a peak incidence of latent syphilis in the last decade. 5 With the accelerated ageing of the global population, the increasing syphilis epidemic among older adults is alarming. Shenzhen, a special economic zone located in southern China and with a population of >10 million, is one of the cities that most affected by syphilis. The reported incidence of syphilis was over 60 per 100 000 in last 10 years, which was much higher than the national incidence. 5,10 Consistent with the aforementioned characteristics of varied age groups, a rapid increase in syphilis incidence was observed among older adults in Shenzhen. 11 Studies usually considered blood donors as a representative of the general population and used the prevalence data of blood donors for real-time surveillance and identification of high-risk groups. 12 Whether the syphilis seroprevalence among blood donors agrees with reported incidence characteristics remains to be studied. Shenzhen follow-up, for syphilis-infected adults. 13 Based on the data from the SPSPC, this study aimed to examine differences in syphilis seroprevalence among blood donors and describe the distribution of serological titres among syphilis-infected donors with respect to age groups, to confirm the syphilis epidemic characteristics in southern China and support the design of effective interventions for older adults.