Adult female syphilis prevalence, congenital syphilis case incidence and adverse birth outcomes, Mongolia 2000e2016: Estimates using the Spectrum STI tool Erdenetungalag Enkhbat a , Eline L. Korenromp b, * , Jugderjav Badrakh a , Setsen Zayasaikhan a , Purevsuren Baya a , Enkhjargal Orgiokhuu a , Narantuya Jadambaa c , Sergelen Munkhbaatar d , Delgermaa Khishigjargal e , Narantuya Khad e , Guy Mahian  e f , Naoko Ishikawa g , Davaalkham Jagdagsuren a , Melanie M. Taylor h, i a Mongolia National Centre for Communicable Disease, AIDS/STI Surveillance and Research Department, Ulaanbaatar, 210648, Bayanzurkh District, Nam-Yan-Ju Street, Mongolia b Avenir Health, Geneva, Switzerland, 1 route de Morillons / 150 Route de Ferney (WCC, Office 164), PO Box 2100, CH-1211 Geneva 2, Switzerland c World Health Organization, Post Box 663, Ulaanbaatar-13, Mongolia d Mongolia Global Fund Supported Project on AIDS and TB, Peace Avenue 13/3, Sukhbaatar District, Ulaanbaatar, Mongolia e Mongolia Center for Health Development, Enkhtaivan Street - 13b, Sukhbaatar District, Ulaanbaatar, Mongolia f Avenir Health, 655 Winding Brook Drive, Glastonbury, CT, CT-06033, USA g World Health Organization, Western Pacific Regional Office, PO Box 2932 (United Nations Avenue), 1000 Manila, Philippines h World Health Organization, Department of Reproductive Health and Research, 8 Avenue Appia (L152),1211 Geneva, Switzerland i Centers for Disease Control and Prevention, Atlanta GA, USA article info Article history: Received 15 December 2017 Received in revised form 26 February 2018 Accepted 8 March 2018 Available online 9 March 2018 Handling Editor: Jianhong Wu Keywords: Syphilis Congenital syphilis Surveillance Screening Antenatal care Epidemiological modelling abstract Introduction: Mongolia's health ministry prioritizes control of Sexually Transmitted In- fections, including syphilis screening and treatment in antenatal care (ANC). Methods: Adult syphilis prevalence trends were fitted using the Spectrum-STI estimation tool, using data from ANC surveys and routine screening over 1997e2016. Estimates were combined with programmatic data to estimate numbers of treated and untreated pregnant women with syphilis and associated incidence congenital syphilis (CS) and CS-attributable adverse birth outcomes (ABO), which we compared with CS case reports. Results: Syphilis prevalence in pregnant women was estimated at 1.7% in 2000 and 3.0% in 2016. We estimated 652 CS cases, of which 410 ABO, in 2016. Far larger, annually increasing numbers of CS cases and ABO were estimated to have been prevented: 1654 cases, of which 789 ABO in 2016  thanks to increasing coverages of ANC (99% in 2016), ANC-based screening (97% in 2016) and treatment of women diagnosed (81% in 2016). The 42 CS cases Abbreviations: ABO, Adverse Birth Outcome; ANC, antenatal care; ANC-1, attendance of antenatal care at least once during a pregnancy; CI, confidence interval; CS, Congenital Syphilis; F, women; N, sample size tested; NCCD, Mongolia National Center for Communicable Diseases; RPR, Rapid Plasma Reagin test; STI, sexually transmitted infection; TP, Treponema pallidum; WHO, World Health Organization. * Corresponding author. E-mail addresses: tungaa1126@gmail.com, e.erdenetungalag@nccd.gov.mn (E. Enkhbat), ekorenromp@avenirhealth.org (E.L. Korenromp), b_juugee@ yahoo.com (J. Badrakh), setsenzaya@gmail.com (S. Zayasaikhan), puje9998@gmail.com, puje_7008@yahoo.com (P. Baya), enkhjargal_o@yahoo.com (E. Orgiokhuu), jadambaan@who.int (N. Jadambaa), sergelen@aids.mn (S. Munkhbaatar), hsic2004@yahoo.com, kh.deegii_0310@yahoo.com (D. Khishigjargal), khadnaraa@yahoo.com (N. Khad), GMahiane@avenirhealth.org (G. Mahian e), ishikawan@who.int (N. Ishikawa), j.davaalkham@nccd.gov.mn, j.davaalkham@ gmail.com (D. Jagdagsuren), mtaylor@who.int (M.M. Taylor). Peer review under responsibility of KeAi Communications Co., Ltd. Contents lists available at ScienceDirect Infectious Disease Modelling journal homepage: www.keaipublishing.com/idm https://doi.org/10.1016/j.idm.2018.03.003 2468-0427/© 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Infectious Disease Modelling 3 (2018) 13e22