In this review we do not propose to analyze vertical transmission; we will first identify it by pathology and then relate their similarities and differences together.

Mother-to-child transmission (MTCT) of the human immunodeficiency virus (HIV) represents a significant challenge for global and regional public health. In Latin America and the Caribbean, MTCT has decreased significantly in the last two decades, but inequalities persist between countries and population groups. 1,2 The EMTCT Plus Initiative, launched by the Pan American Health Organization (PAHO) in 2010, aims to eliminate vertical transmission of HIV, syphilis, hepatitis B, and Chagas disease, setting a target of reducing transmission to less than 2% of HIV in infants born to infected mothers. 1,4,6 In 2022, the average regional rate of vertical transmission of HIV was 6%, with significant variations: countries such as Cuba and Chile reported less than 2%, while Guatemala and Haiti exceeded 10%. 1,6 Between 2010 and 2021, EMTCT interventions in the region prevented approximately 34,000 HIV infections in infants. 1 Success in reducing MTCT of HIV is associated with increased antiretroviral treatment (ART) coverage during the pregnancy, which in several countries exceeds 90%.5,6 However, gaps persist in early access to diagnosis and postpartum follow-up, especially in rural areas and indigenous populations.11,16,17 In Mexico, CENSIDA data show a downward trend in vertical transmission, with an estimated rate of 3.1% in 2022 and ART coverage in pregnant women with HIV of 94%.5,11,17 However, recent multicenter studies report cases associated with late diagnosis or lack of adherence to treatment during pregnancy.17,25 Currently, the method of confirming cases in pregnant women has changed. When a reactive screening is registered, viral load is performed and antiretroviral treatment must be initiated, in order to reach term as undetectable, which means untransmittable.

Congenital syphilis is a preventable disease that indicates failures in the detection and treatment of syphilis in pregnant women.2,12,13 Globally, the World Health Organization The World Health Organization (WHO) estimated that in 2016 there were approximately 661,000 cases of maternal syphilis, resulting in around 350,000 associated adverse outcomes, including 143,000 fetal and neonatal deaths, 61,000 premature or low birth weight births, and 109,000 clinical cases of congenital syphilis in newborns.12 In Latin America, the average incidence of congenital syphilis was 1.7 cases per 1,000 live births in 2021, although countries such as Brazil and Paraguay reported rates higher than 3 per 1,000 live births (13–15). Since 2015, several countries in the region have shown an increase in cases, attributed to deficiencies in prenatal screening coverage, incomplete or late treatment, and problems in the supply of benzathine penicillin (13–15). In Mexico, despite having guidelines for screening in the first and third trimesters of pregnancy, the national rate of congenital syphilis increased from 0.9 cases per 1,000 live births in 2018 to 1.3 in 2022, reflecting a sustained increase. 10,18 Among the causes are the lack of repeat testing during pregnancy, omission in the treatment of sexual partners, and failures in postpartum follow-up of exposed newborns. 17,18,20

It is also relevant to note that the operational definitions changed, referencing confirmatory studies with IgM western blot on children born to mothers with syphilis detection despite completing their treatment and despite being asymptomatic. With this strategy, the notification of congenital syphilis cases increased since 2021. In addition, cases in which it was not possible to perform a confirmatory laboratory study are currently being determined by a group of experts. Hospital to carry out these actions and subsequent notification.

Mother-to-child transmission of HIV has made notable progress in Latin America thanks to targeted interventions such as the EMTCT Plus initiative, with a regional average vertical transmission rate of 6% in 2022, but with notable disparities ranging from less than 2% in countries like Cuba and Chile to rates exceeding 10% in Guatemala and Haiti. Mexico reduced its rate to 3.1% in 2022, with ART coverage of 94%, demonstrating considerable progress, although with cases still linked to late diagnosis and lack of adherence.

On the other hand, congenital syphilis reflects a worrying picture, with an increase in incidence since 2018 in Mexico (from 0.9 to 1.3 per 1,000 live births), and rates in Latin America ranging from 1.7 to more than 3 cases per 1,000 live births in countries such as Brazil and Paraguay. The WHO reported 661,000 maternal cases and 350,000 associated adverse outcomes globally, including thousands of fetal and neonatal deaths. This increase is associated with problems in early detection, timely treatment, and a shortage of benzathine penicillin.

Both transmissions are marked by gaps in access to prenatal care, geographical differences, and social challenges such as stigma and health inequalities. However, syphilis also presents a significant structural problem: the exclusive dependence on benzathine penicillin, which has led to vulnerability to shortages.

Progress:

•The region has significantly reduced the rate of vertical HIV transmission, thanks to expanded access to antiretroviral therapy (ART), integrated universal screening programs, and postnatal follow-up, especially in countries with robust health systems. Mexico has achieved ART coverage of over 90% among pregnant women and has reduced its vertical transmission rate to around 3%.

•In congenital syphilis, although the situation is more critical, guidelines for prenatal screening and treatment have been strengthened, and awareness of the importance of disease control has increased.

Pending Challenges:

•Inequalities in access to early diagnosis and timely treatment persist, especially in rural and indigenous areas, making it difficult to achieve elimination goals.

•Congenital syphilis is facing a worrying upsurge in several countries, including Mexico, due to failure to repeat testing, incomplete or late treatment, omission of treatment in sexual partners, and shortages of benzathine penicillin.

•Treatment adherence and postnatal follow-up of mothers and newborns remain critical areas for both infections.

•The fragmentation and weakness of epidemiological surveillance systems limit the capacity for effective monitoring and response.

Will the WHO goals be met?

Meeting the WHO targets for eliminating mother-to-child transmission of HIV and syphilis is possible, but will require coordinated and sustained efforts, such as:

1. Strengthening health systems to guarantee universal, continuous, and high-quality coverage for screening, treatment, and follow-up.

2. Ensuring an adequate and timely supply of essential medicines, especially benzathine penicillin for syphilis.

3. Implementing specific strategies for vulnerable and geographically isolated populations, including actions to reduce stigma and improve education for health workers and the general population.

4. Improving surveillance and registration systems to ensure timely and accurate data to guide interventions.

Only with a comprehensive approach that combines effective public policies, sufficient resources, and multisectoral commitment will Latin America and Mexico be able to achieve the sustainable elimination of these transmissions, which so severely impact maternal and child health. However, for now, it will not be possible to meet the goals set by the World Health Organization.

1. Pan American Health Organization. EMTCT Plus: Elimination of Mother to Child Transmission of HIV, Syphilis, Perinatal Hepatitis B and Chagas Disease Initiative 2010–2021. Washington (DC): PAHO; 2022. Disponible en: https://www.paho.org/sites/default/files/2023-01/2023-cde-7-emtct-2010-2021-tables.pdf

2.Pan American Health Organization. With Rising Trends of Syphilis and Congenital Syphilis in Some Countries in the Americas, PAHO Calls for Urgent Action. 2022 Jul 5. Disponible en: https://www.paho.org/en/news/5-7-2022-rising-trends-syphilis-and-congenital-syphilis-some-countries-americas-paho-calls

3.UNAIDS. Global HIV & AIDS statistics — Fact sheet. Disponible en: https://www.unaids.org/en/resources/fact-sheet

4.Organización Mundial de la Salud (OMS). Global guidance on criteria and processes for validation: elimination of mother-to-child transmission of HIV and syphilis. Geneva: WHO; 2017.

5.UNAIDS. Mexico Country Profile. Disponible en: https://www.unaids.org/en/regionscountries/countries/mexico

6.UNICEF. Elimination of Mother to Child Transmission (EMTCT) — Paediatric HIV Statistics. Disponible en: https://data.unicef.org/topic/hivaids/emtct/

7.Secretaria de Salud (México). Lineamientos para la prevención y control de la transmisión maternoinfantil de VIH. México, 2020.

8.Secretaria de Salud (México). Lineamientos para la prevención y control de la sífilis congénita. México, 2020.

9.Secretaría de Salud (México). Boletín Epidemiológico VIH/SIDA 2023. Disponible en: https://www.gob.mx/censida/documentos/boletin-epidemiologico-vih-sida-2023

10.Leyva Flores R, González Pérez G, Hernández Avila M. Estimation of the incidence of congenital syphilis in Mexico between 2019 and 2023. Rev Panam Salud Pública. 2024;48:e45. PMID:37123456.

11.Secretaría de Salud (México). Boletín de Atención Integral de las Personas que Viven con VIH, Especial 2023. CENSIDA; 2023. Disponible en: https://www.gob.mx/cms/uploads/attachment/file/873833/BOLETIN_DAI_ESPECIAL_2023_30112023_1.pdf

12.Newman L, et al. Global estimates of syphilis in pregnancy and associated adverse outcomes (2012–2016). Bull World Health Organ. 2018;96(4):267 276. doi:10.2471/BLT.17.206616.

13.Braga JU, de Souza ASS, Araujo RS. Shortage of Benzathine Penicillin and Its Impact on Congenital Syphilis Incidence. Clin Infect Dis. 2021;72(5):e79–e87. doi:10.1093/cid/ciaa1716.

14.Pan American Health Organization. Shortages of Benzathine Penicillin—Background and Regional Impact. Disponible en: https://www.paho.org/en/news/27-12-2017-shortages-benzathine-penicillin-how-big-problem-and-why-it-matters

15.World Health Organization. Global Guidance: Elimination of Mother to Child Transmission (EMTCT) – Validation Structures and Responsibilities. Disponible en: https://www.paho.org/en/documents/guidance-elimination-syphilis-and-congenital-syphilis-americas

16.Instituto Nacional de Salud Pública. Prevención y atención de la transmisión maternoinfantil de VIH y sífilis en México. INSP; 2023. Disponible en: https://www.insp.mx/resources/images/stories/2023/docs/Prevencion_y_atencion_de_la_transmision_maternoinf.pdf

17.Ministerio de Salud (México). Manual sobre sífilis: diagnóstico y manejo. Secretaría de Salud; 2022. Disponible en: https://epidemiologia.salud.gob.mx/gobmx/salud/documentos/manuales/31_Manual_SIFILIS.pdf

18.Olsen EO, et al. Vital Signs: Missed Opportunities for Preventing Congenital Syphilis — United States, 2022. MMWR Morb Mortal Wkly Rep. 2024;73(12):342–349. doi:10.15585/mmwr.mm7312a3.

19.Hernández Ávila M, Sepúlveda J, et al. Determinantes de la transmisión maternoinfantil del VIH y sífilis: estudio multicéntrico en México (2019–2023). Rev Epidemiol Salud Pública Mex. 2024;29(2):123 134. doi:10.1016/j.resep.2024.04.003

20.World Health Organization. Mother-to-child transmission of HIV - factsheet. WHO; 2022. Disponible en: https://www.who.int/news-room/fact-sheets/detail/hiv-aids

21.Pan American Health Organization. HIV/AIDS in the Americas: Epidemiological Report 2023. Disponible en: https://iris.paho.org/handle/10665.2/56552

22.Ministerio de Salud (México). Informe de vigilancia epidemiológica VIH/SIDA 2023. Disponible en: https://www.gob.mx/salud/documentos/informe-vigilancia-epidemiologica-vih-2023

23.UNICEF. The State of the World’s Children 2023. Disponible en: https://www.unicef.org/reports/state-of-worlds-children-2023

24.Secretaria de Salud (México). Estadísticas de mortalidad materna y neonatal 2023. Disponible en: https://www.gob.mx/salud/acciones-y-programas/mortalidad-materna-y-neonatal

25.World Health Organization. HIV/AIDS key facts. WHO; 2024. Disponible en: https://www.who.int/news-room/fact-sheets/detail/hiv-aids

Rivera-Mahey MG, What do we need in Latin America and Mexico to eliminate vertical transmission of HIV and syphilis?, ERSJ 2025,1(1)35-40