{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T12:02:22Z","timestamp":1784721742748,"version":"3.55.0"},"reference-count":44,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T00:00:00Z","timestamp":1784678400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the Sanming Project of Medicine in Shenzhen, Shenzhen Municipal Health Commission","award":["SZSM202311032"],"award-info":[{"award-number":["SZSM202311032"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathogens"],"abstract":"<jats:p>Over the past decade, the incidence of infectious syphilis has been on the rise in the general Chinese population. Consequently, Treponema Pallidum (TP) testing has been proposed as a surrogate marker for sexually transmitted pathogens and for monitoring risky sexual behaviors among blood donors globally. In addition, sexual contact with individuals chronically infected with hepatitis B virus (HBV) is recognized as one of the primary routes of HBV transmission. Blood donors may acquire HBV infection through sexual contact with chronically infected partners, particularly with occult hepatitis B infections (OBIs), which are characterized by intermittent and extremely low viral loads. Therefore, the prevalence of OBIs among syphilis-positive blood donations and the corresponding risks to blood safety require further investigation. This study aimed to investigate the prevalence of OBIs among syphilis-positive blood donors and assess the surrogate value of TP testing for evaluating OBI-related risks to blood supply. After routine screening using serological assays and nucleic acid testing (NAT), blood donation samples with positive anti-TP enzyme-linked immunosorbent assay (ELISA) results were collected and further confirmed by the Treponema Pallidum Particle Agglutination Assay (TPPA). For blood donations confirmed positive for syphilis, further tests were performed to characterize whether the donations had HBV co-infection, including electrochemiluminescence immunoassay (ECLI) for the detection of hepatitis B surface antigen (HBsAg), anti-hepatitis B surface antibody (anti-HBs), hepatitis B e antigen (HBeAg), anti-hepatitis B e antibody (anti-HBe), and anti-hepatitis B core antibody (anti-HBc). Additionally, quantitative real-time polymerase chain reaction (qPCR) was used for HBV DNA quantification, and nested PCRs for the S and basal core promoter\/precore (BCP\/PC) region were conducted in combination with high-volume nucleic acid extraction. Subsequently, molecular characterization of HBV DNA in these co-infected samples was carried out by DNA sequencing to analyze the viral genetic features. Of 252 anti-TP ELISA+ donations screened from 64,871 blood samples, 138 (138\/250, 55.2%) donations were confirmed syphilis-positive but NAT\u2212, among which 78 (78\/138, 56.5%) were anti-HBc-positive, and 88 (88\/138, 63.7%) had anti-HBs. Notably, seven donations (7\/138, 5.1%) were diagnosed as OBI co-infections, and available sequence analysis revealed that three cases were genotype B and one case was genotype C. In addition, several mutations in the S region of the HBV genome were identified, including Q101R, K122R, Q129H, T131N, M133T, G145R, and Y161F mutations. Furthermore, nucleotide mutations such as T1719G, A1752T, G1896A, and A1762T\/G1764A in the BCP\/PC regions were also detected in these OBI donations. These mutations may contribute to the extremely low HBV viral loads and\/or failure in HBsAg detection, collectively leading to OBIs. These data indicate that syphilis screening of blood donors has potential to serve as an additional safeguard measure for excluding donations co-infected with OBIs. The high prevalence of undetected OBIs in syphilis-positive blood donors further supports that syphilis screening has the potential to serve as a surrogate marker for HBV-related risks in the blood supply.<\/jats:p>","DOI":"10.3390\/pathogens15070776","type":"journal-article","created":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T10:48:28Z","timestamp":1784717308000},"page":"776","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["High Prevalence of Occult Hepatitis B Virus Co-Infection Identified in Treponema Pallidum-Positive Blood Donations: Implications for HBV Risk Reduction"],"prefix":"10.3390","volume":"15","author":[{"given":"Xianlin","family":"Ye","sequence":"first","affiliation":[{"name":"Department of Laboratory, Shenzhen Blood Center, Shenzhen 518035, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaoxuan","family":"Xu","sequence":"additional","affiliation":[{"name":"Department of Laboratory, Shenzhen Blood Center, Shenzhen 518035, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jinfeng","family":"Zeng","sequence":"additional","affiliation":[{"name":"Department of Laboratory, Shenzhen Blood Center, Shenzhen 518035, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"He","family":"Xie","sequence":"additional","affiliation":[{"name":"The Hospital of Xidian Group, Xi\u2019an 710077, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jujun","family":"Sun","sequence":"additional","affiliation":[{"name":"The Hospital of Xidian Group, Xi\u2019an 710077, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Baoren","family":"He","sequence":"additional","affiliation":[{"name":"The Joint-Laboratory of Transfusion-Transmitted Diseases (TTDs) Between IBT, CAMS and Nanning Blood Center, Nanning Blood Center, Nanning 530003, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Limin","family":"Chen","sequence":"additional","affiliation":[{"name":"The Hospital of Xidian Group, Xi\u2019an 710077, China"},{"name":"The Joint-Laboratory of Transfusion-Transmitted Diseases (TTDs) Between IBT, CAMS and Nanning Blood Center, Nanning Blood Center, Nanning 530003, China"},{"name":"Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion (IBT), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Chengdu 610052, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1128\/CMR.12.2.187","article-title":"Syphilis: Review with emphasis on clinical, epidemiologic, and some biologic features","volume":"12","author":"Singh","year":"1999","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_2","unstructured":"World Health Organization (WHO) (2009, January 01). Screening Donated Blood for Transfusion-Transmissible Infections: Recommendations. Available online: https:\/\/www.who.int\/publications\/i\/item\/9789241547888."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1128\/CMR.19.1.29-49.2006","article-title":"Biological basis for syphilis","volume":"19","author":"Lafond","year":"2006","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"195","DOI":"10.1186\/s13643-017-0595-3","article-title":"Syphilis in the Americas: A protocol for a systematic review of syphilis prevalence and incidence in four high-risk groups, 1980\u20132016","volume":"6","author":"Kitayama","year":"2017","journal-title":"Syst. Rev."},{"key":"ref_5","first-page":"197","article-title":"Syphilis testing in blood donors: An update","volume":"13","author":"Kaur","year":"2015","journal-title":"Blood Transfus."},{"key":"ref_6","first-page":"e6","article-title":"Syphilis in China: The great comeback","volume":"1","author":"Hesketh","year":"2008","journal-title":"Emerg. Health Threat. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"136","DOI":"10.1093\/cid\/ciz331","article-title":"A Nationwide Spatiotemporal Analysis of Syphilis over 21 Years and Implications for Prevention and Control in China","volume":"70","author":"Tao","year":"2020","journal-title":"Clin. Infect. Dis."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e259","DOI":"10.1016\/j.ijid.2012.10.006","article-title":"The prevalence and trends of transfusion-transmissible infectious pathogens among first-time, voluntary blood donors in Xi\u2019an, China between 1999 and 2009","volume":"17","author":"Ji","year":"2013","journal-title":"Int. J. Infect. Dis."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Song, Y., Bian, Y., Petzold, M., and Ung, C.O. (2014). Prevalence and trend of major transfusion-transmissible infections among blood donors in Western China, 2005 through 2010. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0094528"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e29006","DOI":"10.1002\/jmv.29006","article-title":"The high prevalence of occult hepatitis B infections among the partners of chronically infected HBV blood donors emphasizes the potential residual risk to blood safety","volume":"95","author":"Ye","year":"2023","journal-title":"J. Med. Virol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"6431","DOI":"10.2147\/IDR.S386495","article-title":"Prevalence of Syphilis Infections Among Volunteer Blood Donors in Jinan Blood Center, China: A 15-Year Retrospective Study","volume":"15","author":"Chen","year":"2022","journal-title":"Infect. Drug Resist."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1476","DOI":"10.1111\/trf.15824","article-title":"Comprehensive Analysis of Hepatitis B Virus Infections in Blood Donors in Southern China That Are Surface Antigen Positive but Nucleic Acid Testing Negative","volume":"7","author":"Ye","year":"2020","journal-title":"Transfusion"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2419","DOI":"10.1182\/blood-2002-04-1084","article-title":"The risk of hepatitis B virus infection by transfusion in Kumasi, Ghana","volume":"101","author":"Allain","year":"2003","journal-title":"Blood"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e70396","DOI":"10.1002\/jmv.70396","article-title":"High Genetic Variability of Hepatitis B Virus in Blood Donors with Surface Antigen Positive But DNA Negative in Southern China","volume":"97","author":"Ye","year":"2025","journal-title":"J. Med. Virol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1111\/vox.12446","article-title":"Refining the risk estimate for transfusion-transmission of occult hepatitis B virus","volume":"112","author":"Seed","year":"2017","journal-title":"Vox Sang."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1068","DOI":"10.1016\/j.jhep.2015.06.016","article-title":"Poor Efficacy of Nucleic Acid Testing in Identifying Occult HBV Infection and Consequences for Safety of Blood Supply in Italy","volume":"63","author":"Spreafico","year":"2015","journal-title":"J. Hepatol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1111\/trf.17707","article-title":"Syphilis seroprevalence and incidence in US blood donors from 2020 to 2022","volume":"64","author":"Conti","year":"2024","journal-title":"Transfusion"},{"key":"ref_18","first-page":"163","article-title":"Seroreactivity and prevalence of syphilis in donors at a blood bank in Barranquilla, Colombia","volume":"39","year":"2019","journal-title":"Biomedica"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Alharazi, T., Alzubiery, T.K., Alcantara, J.C., Qanash, H., Bazaid, A.S., Altayar, M.A., and Aldarhami, A. (2022). Prevalence of Transfusion-Transmitted Infections (HCV, HIV, Syphilis and Malaria) in Blood Donors: A Large-Scale Cross-Sectional Study. Pathogens, 11.","DOI":"10.3390\/pathogens11070726"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1186\/s40249-017-0255-9","article-title":"Seroprevalence of hepatitis B, hepatitis C, human immunodeficiency virus, Treponema pallidum, and co-infections among blood donors in Kyrgyzstan: A retrospective analysis (2013\u20132015)","volume":"6","author":"Karabaev","year":"2017","journal-title":"Infect. Dis. Poverty"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"562","DOI":"10.12688\/f1000research.17983.1","article-title":"HIV, syphilis and hepatitis B coinfections in Mkushi, Zambia: A cross-sectional study","volume":"8","author":"Katamba","year":"2019","journal-title":"F1000 Res."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Xie, D.D., Li, J., Chen, J.T., Eyi, U.M., Matesa, R.A., Obono, M.M., Ehapo, C.S., Yang, L.Y., Yang, H., and Yang, H.T. (2015). Seroprevalence of Human Immunodeficiency Virus, Hepatitis B Virus, Hepatitis C Virus, and Treponema pallidum Infections among Blood Donors on Bioko Island, Equatorial Guinea. PLoS ONE, 10.","DOI":"10.1371\/journal.pone.0139947"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"103704","DOI":"10.1016\/j.bjid.2023.103704","article-title":"Seroprevalence of viral transfusion transmissible infections (HBsAg, anti-HCV, anti-HIV, Syphilis) and coinfection among healthy volunteer blood donors during 5-years in Luanda, Angola","volume":"27","author":"Quintas","year":"2023","journal-title":"Braz. J. Infect. Dis."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1186\/2052-1839-14-5","article-title":"HIV, HBV, HCV and T. pallidum infections among blood donors and Transfusion-related complications among recipients at the Laquintinie hospital in Douala, Cameroon","volume":"14","author":"Mbangue","year":"2014","journal-title":"BMC Hematol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"369","DOI":"10.1097\/OLQ.0000000000000291","article-title":"Estimating the Public Health Burden Associated with Adverse Pregnancy Outcomes Resulting from Syphilis Infection Across 43 Countries in Sub-Saharan Africa","volume":"42","author":"Kuznik","year":"2015","journal-title":"Sex. Transm. Dis."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"75","DOI":"10.11604\/pamj.2016.24.75.8425","article-title":"A study on usefulness of a set of known risk factors in predicting maternal syphilis infections in three districts of Western Province, Zambia","volume":"24","author":"Sakala","year":"2016","journal-title":"Pan Afr. Med. J."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"778","DOI":"10.1186\/s12879-021-06505-w","article-title":"Sero-epidemiology and associated factors of HIV, HBV, HCV and syphilis among blood donors in Ethiopia: A systematic review and meta-analysis","volume":"21","author":"Melku","year":"2021","journal-title":"BMC Infect. Dis."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"9316","DOI":"10.1038\/s41598-025-94332-3","article-title":"A systematic review and meta-analysis of the prevalence and risk of syphilis among blood donors in Thailand","volume":"15","author":"Rattanatham","year":"2025","journal-title":"Sci. Rep."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"e024393","DOI":"10.1136\/bmjopen-2018-024393","article-title":"Association between syphilis seroprevalence and age among blood donors in Southern China: An observational study from 2014 to 2017","volume":"9","author":"Wu","year":"2019","journal-title":"BMJ Open"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1007\/s10441-014-9242-8","article-title":"HIV transmissions by stage and sex role in long-term concurrent sexual partnerships","volume":"63","author":"Kim","year":"2015","journal-title":"Acta Biotheor."},{"key":"ref_31","first-page":"641","article-title":"Trend of syphilis infection among voluntary blood donors in Foshan City from 2008 to 2017","volume":"28","author":"Lin","year":"2020","journal-title":"J. Exp. Hematol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1668703","DOI":"10.1155\/2022\/1668703","article-title":"Prevalence of Treponema Pallidum Antibody among Volunteer Blood Donors in China","volume":"2022","author":"Zheng","year":"2022","journal-title":"Can. J. Infect. Dis. Med. Microbiol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1186\/s12879-019-4128-7","article-title":"Seroprevalence and risk factors on Syphilis among blood donors in Chengdu, China, from 2005 to 2017","volume":"19","author":"Liu","year":"2019","journal-title":"BMC Infect. Dis."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"655","DOI":"10.1111\/j.1537-2995.2008.02042.x","article-title":"Current value of serologic test for syphilis as a surrogate marker for blood-borne viral infections among blood donors in the United States","volume":"49","author":"Zou","year":"2009","journal-title":"Transfusion"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2241","DOI":"10.1111\/trf.18050","article-title":"Transfusion-transmissible coinfections among US blood donors","volume":"64","author":"Conti","year":"2024","journal-title":"Transfusion"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1195","DOI":"10.1111\/trf.17393","article-title":"Monitoring syphilis serology in blood donors: Is there utility as a surrogate marker of early transfusion transmissible infection behavioral risk?","volume":"63","author":"Drews","year":"2023","journal-title":"Transfusion"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1002\/jmv.24912","article-title":"High prevalence of syphilis, HBV, and HCV co-infection, and low rate of effective vaccination against hepatitis B in HIV-infected patients in West China hospital","volume":"90","author":"Yang","year":"2018","journal-title":"J. Med. Virol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1741","DOI":"10.1111\/j.1537-2995.2011.03527.x","article-title":"NHLBI Retrovirus Epidemiology Donor Study-II (REDS-II), International Component. The increasing prevalence of serologic markers for syphilis among Chinese blood donors in 2008 through 2010 during a syphilis epidemic","volume":"52","author":"Liu","year":"2012","journal-title":"Transfusion"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1038\/s41598-017-00035-9","article-title":"Status of HBsAg seroprevalence in 15 million rural couples in China: A cross-sectional study","volume":"21","author":"Zhang","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1111\/jvh.12693","article-title":"Prevalence of HBsAg\/HBeAg amongst 1 936 801 couples preparing for pregnancy in rural China: An observational study","volume":"24","author":"Liu","year":"2017","journal-title":"J. Viral Hepat."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"236","DOI":"10.1056\/NEJMoa1007644","article-title":"Nucleic acid testing to detect HBV infection in blood donors","volume":"364","author":"Stramer","year":"2011","journal-title":"N. Engl. J. Med."},{"key":"ref_42","first-page":"6","article-title":"Characterization and follow-up study of occult hepatitis B virus infection in anti-HBc-positive qualified blood donors in southern China","volume":"15","author":"Ye","year":"2017","journal-title":"Blood Transfus."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"890","DOI":"10.1111\/trf.12902","article-title":"High prevalence of anti-hepatitis\u2009B core antigen in hepatitis\u2009B virus-vaccinated Chinese blood donors suggests insufficient protection but little threat to the blood supply","volume":"55","author":"Zheng","year":"2015","journal-title":"Transfusion"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1111\/vox.12874","article-title":"Is sexual risk behaviour associated with an increased risk of transfusion-transmissible infections in blood donors from Western and Pacific countries? A systematic review and meta-analysis","volume":"115","author":"Matthysen","year":"2020","journal-title":"Vox Sang."}],"container-title":["Pathogens"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-0817\/15\/7\/776\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,22]],"date-time":"2026-07-22T11:16:23Z","timestamp":1784718983000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-0817\/15\/7\/776"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,22]]},"references-count":44,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["pathogens15070776"],"URL":"https:\/\/doi.org\/10.3390\/pathogens15070776","relation":{},"ISSN":["2076-0817"],"issn-type":[{"value":"2076-0817","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,22]]}}}