About

William B. MacLeod is a Research Associate Professor in the Department of Global Health at Boston University School of Public Health. He is a public health data scientist with training in demography, epidemiology, and biostatistics. His work focuses on answering policy-relevant programmatic questions related to the management of HIV treatment programs. Bill has been based in South Africa for the past seven years, where he has collaborated on research and monitoring & evaluation projects with South African government institutions. He is the Co-Principal Investigator of a USAID-funded project that has developed dashboards and tools for monitoring the HIV treatment program in South Africa. MacLeod is recognized internationally as an expert on clinical trials and has served on Data Safety and Monitoring Boards and Technical Advisory Groups for WHO and CDC sponsored international studies. His educational background includes a Doctor of Science and a Master of Science in Population and International Health from Harvard School of Public Health, and a Bachelor's degree in International Relations from the University of California at Davis.

Research topics

• Medicine
• Environmental health
• Pediatrics
• Political Science
• Biology
• Computer Science
• Internal medicine
• Demography
• Pathology
• Genetics
• Virology
• Immunology
• Nursing
• Data science

Selected publications

• Monitoring for advanced disease in the universal test and treat era: trends in CD4 count testing in South Africa

  BMC Global and Public Health · 2025-01-02 · 7 citations

  articleOpen access

  BACKGROUND: Under South Africa's Universal Test and Treat (UTT) policy, CD4 counts are no longer required to determine HIV treatment eligibility. However, CD4 count at presentation remains an important marker of disease progression. We assessed whether CD4 testing declined in the UTT era and, if so, by how much. METHODS: We analysed CD4 count data from the National Health Laboratory Service (NHLS) National HIV Cohort and TIER.Net database for individuals in HIV care across five South African provinces. "First CD4 count" was defined as the first CD4 test recorded for each patient. In TIER.Net, "date of presentation" was the earliest date of HIV testing, CD4 measurement, or clinic visit. Trends in first CD4 testing volumes (2004-2018) were analyzed, with interrupted time-series analyses assessing the impact of UTT (September 2016). RESULTS: Data included 5,274,218 (NHLS) and 2,265,557 (TIER.Net) individuals with a first CD4 count. In NHLS, first CD4 counts increased from 47,604 in 2004 to 383,705 in 2010 and then declined. Lower volumes were recorded in TIER.Net. Adjusting for prior trends, first CD4 counts increased slightly after UTT, by 32 individuals/day in NHLS (95% CI: - 6 to 61) and 88 individuals/day in TIER.Net (95% CI: 30 to 148). Among TIER.Net patients, the percentage with a CD4 count decreased by 4.3% (95% CI: - 5.2 to - 3.0%). CONCLUSIONS: We found no major decline in CD4 testing at presentation following UTT, contrasting findings from resource-constrained settings with greater reliance on external donors.

  PublisherOA PDFDOI

• Longitudinal Analysis of Nasopharyngeal Microbial Risk Markers for Fatal Acute Febrile Illness in a Zambian Birth Cohort

  The Journal of Infectious Diseases · 2025-05-30

  articleOpen access

  BACKGROUND: Fatal acute febrile illness (fAFI) is a known predecessor of many infant mortality events in low-resource settings, but early risk markers for this condition remain poorly understood. Nasopharyngeal (NP) microbiome patterns may influence the severity of these infections. METHODS: We analyzed longitudinal changes in the NP microbiota of Zambian infants with fAFI onset compared to healthy controls, aiming to identify microbial indicators associated with severe illness outcomes. We conducted a pooled analysis of a longitudinal nested case-control study composed of 26 samples from 9 infants who developed fAFI compared with 69 samples from 10 healthy infants. Infants underwent nasopharyngeal sampling from 1 week through 14 weeks of age at 2-2.5-week intervals. We performed 16S rRNA gene amplicon sequencing on all infant NP samples and characterized NP microbiome maturation among infants with febrile acute febrile illness (fAFI+) and healthy controls (fAFI-). RESULTS: Beta diversity measures of fAFI- infants were markedly higher than those of fAFI+ infants. The fAFI+ infant NP microbiome was marked by lower abundances of Dolosigranulum, Haemophilus, Streptococcus, and Corynebacterium, with higher relative presence of Pseudomonas. CONCLUSIONS: Our findings suggest that specific microbial community patterns and early NP microbiome dysbiosis may be associated with increased illness risk. These findings can motivate further studies to inform foundational markers for fAFI in infants, contributing to precision pediatric care.

  PublisherOA PDFDOI

• Record linkage without patient identifiers: Proof of concept using data from South Africa’s national HIV program

  PLOS Global Public Health · 2025-07-09 · 1 citations

  articleOpen access

  Linkage between health databases typically requires patient identifiers such as names and personal identification numbers. We developed and validated a record linkage strategy to combine administrative health databases without identifiers for South Africa's public sector HIV program. We linked CD4 counts and HIV viral loads from South Africa's TIER.Net with the National Health Laboratory Service (NHLS) database for patients receiving care between 2015-2019 in Ekurhuleni District (Gauteng Province). Linkage variables were result value, specimen collection date, facility of collection, year and month of birth, and sex. We used three matching strategies: exact matching on exact values of all variables, caliper matching allowing a ± 5 day window on result date, and specimen barcode matching using unique specimen identifiers. A sequential linkage approach applied specimen barcode, followed by exact, and then caliper matching. Exact and caliper matching were validated using barcodes (available for 34% of records in TIER.Net) as a "gold standard". Performance measures were sensitivity, positive predictive value (PPV), share of patients linked, and percent increase in data points. We attempted to link 2,017,290 laboratory test results from TIER.Net (523,558 unique patients) with 2,414,059 NHLS test results. Exact matching achieved 69.0% sensitivity and 95.1% PPV. Caliper matching achieved 75% sensitivity and 94.5% PPV. Sequential linkage matched 41.9% using specimen barcodes, 51.3% through exact matching, and 6.8% through caliper matching, for 71.9% (95% CI: 71.9, 72.0) of test results matched overall, with 96.8% (95% CI: 96.7, 97.1) PPV and 85.9% (95% CI: 85.7, 85.9) sensitivity. This linked 86.0% (95% CI: 85.9, 86.1) of TIER.Net patients to the NHLS (N = 1,450,087), increasing laboratory results in TIER.Net by 62.6%. Linkage of TIER.Net and NHLS without patient identifiers attained high accuracy and yield without compromising privacy. The integrated cohort provides a more complete laboratory test history and supports more accurate HIV program indicator estimates.

  PublisherDOI

• Timing of ART Initiation With Treatment Policy Changes in South Africa: A Cohort Study

  JAIDS Journal of Acquired Immune Deficiency Syndromes · 2025-11-18

  articleOpen access

  BACKGROUND: Early antiretroviral therapy (ART) improves uptake, retention, and viral suppression. However, there is limited real-world data for high HIV burden settings, including South Africa. METHODS: We conducted a retrospective cohort study using linked clinical CD4 and viral load (VL) data from South Africa's HIV treatment database (TIER.Net) and National Health Laboratory Service (NHLS). Our analysis included ART non-naive individuals entering HIV care between January 2010 and March 2017 in 4 provinces (KwaZulu-Natal, Northern Cape, Limpopo, and Mpumalanga). We estimated days from entry into HIV care (same day, 2-6 days, 7-89 days, and ≥90 days). Outcome measures included retention, viral suppression (VL <50 copies/mL), and CD4 recovery at 12 months. A Poisson regression model with adjusted Risk Ratios (aRR) was used to identify factors associated with rapid ART initiation (<7 days) at 5% significance level. RESULTS: Among 1,211,966 individuals (median age 31 years, 69.6% female), 30% initiated ART on the day of diagnosis, 4.2% within 2-6 days, 26% within 7-89 days, and 39.8% after ≥90 days. Rapid ART initiation increased over time, with same-day initiations rising from 24.6% in 2010 to 60% in 2017. Factors associated with rapid ART initiation included female gender (aRR: 1.04; 95% CI: 1.03 to 1.04) and a lower CD4 count at entry. At 12 months, 77.6% of same-day initiators were retained, with 28.4% having a VL test and 61.2% achieving viral suppression. CONCLUSIONS: Rapid ART initiation has increased because of policy changes and healthcare worker efforts in South Africa, but addressing late entry into care and treatment nonadherence remains crucial.

  PublisherDOI

• Bordetella pertussis-related Respiratory Deaths in Infants From 4 Days to 6 Months of Age, Results From a 3-Year, Prospective Postmortem Surveillance Study in Lusaka, Zambia

  The Pediatric Infectious Disease Journal · 2025-03-19 · 1 citations

  article1st authorCorresponding

  BACKGROUND: Since the 1990s, a remarkable decline in infant and child mortality has occurred. Continued progress in reducing mortality will need to focus on early infant and neonatal mortality and on less common diseases than pneumonia, diarrhea and malnutrition. One of the candidate diseases for focus is Bordetella pertussis , the principal cause of "whooping cough." METHODS: We conducted a study to measure the burden of deaths and calculate the population-attributable fraction of deaths due to B. pertussis . We collected postmortem nasopharyngeal swabs from subjects who died at the University Teaching Hospital or in the community and were brought to the University Teaching Hospital morgue 4 days to < 6 months of age. Infection with B. pertussis was determined with polymerase chain reaction testing. We assigned respiratory cause of death from the medical record or from a verbal autopsy collected from caregivers. RESULTS: From August 2017 to August 2020, we collected nasopharyngeal samples from 2236 deceased subjects. Respiratory deaths were assigned to 29.0% of the deaths; 39.5% of community deaths were attributed to respiratory causes. Using 2 definitions of polymerase chain reaction positivity, the prevalence of B. pertussis in infant deaths was between 5.69 per 1000 deaths (95% confidence interval, 2.57-8.80) and 25.81 per 1000 deaths (95% confidence interval, 19.24-32.38). Pertussis accounted for between 0.22% and 0.81% of all infant deaths. CONCLUSIONS: In this population of infants, B. pertussis was a minor source of all-cause infant mortality. Our analysis does not support the need for further steps for population-level preventive strategies for the control of B. pertussis .

  PublisherDOI

• Sequential Respiratory Syncytial Virus and Bacterial Infections in the Nasopharynx of Zambian Infants and Mothers

  The Pediatric Infectious Disease Journal · 2025-03-05

  article

  BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of severe respiratory infections in infants, especially under 5 years of age. Several studies have reported that interactions between RSV and bacteria like Streptococcus pneumoniae (SP), Moraxella catarrhalis (MC), Haemophilus influenzae (HI) and Staphylococcus aureus (SA) may influence their pathogenicity and the clinical outcome of infection. However, existing knowledge about RSV-bacterial interactions in infants comes primarily from cross-sectional studies, which cannot evaluate the influence of infection sequence on these interactions. METHODS: We conducted a nested prospective study of the Zambian mother-infant birth cohort, followed for the first 14 weeks of life. Nasopharyngeal samples were collected from both infants and mothers biweekly. We analyzed the sequence of RSV and bacterial detection, and its correlation with RSV and bacterial density, and with severity of symptoms. RESULTS: SP acquisition in infants following RSV infection is associated with lower bacterial densities compared to SP alone. These effects were not observed with Moraxella catarrhalis , Staphylococcus aureus or Haemophilus influenzae , or in the mothers. Additionally, prior RSV did not result in earlier bacterial acquisition. Our data suggests that prior bacterial infection with any of the species did not significantly affect RSV viral loads. Finally, antibiotic exposure in infants did not reduce bacterial density overall, but infants with SP-only infections who received antibiotics showed increased bacterial levels. CONCLUSION: The observed effect of prior RSV on SP density, which was not seen in other bacteria, suggests a specific interaction between RSV and SP that may influence bacterial colonization dynamics differently than other bacterial species, highlighting the need for further investigation into these mechanisms.

  PublisherDOI

• Ready for takeoff? exploring United States health care providers’ pretravel consultation priorities, gaps, barriers, and opportunities

  Travel Medicine and Infectious Disease · 2025-10-01 · 2 citations

  articleOpen access

  Pretravel consultation by healthcare providers (HCPs) with travel medicine expertise can mitigate travel-related health risks. This analysis aimed to understand US-based HCPs' pretravel consultation educational gaps, priorities, barriers, and opportunities. An electronic survey was conducted May-June 2024, using a convenience sample of HCPs identified through the Med Learning Group and travel specialists from the International Society of Travel Medicine and American Society of Tropical Medicine and Hygiene. In total, 205 HCPs completed the survey, including physicians (50 %), nurse practitioners (19 %), nurses (12 %), pharmacists (11 %), physician associates (7 %). Most (66 %) provided pretravel consultations and only 21 % held formal travel medicine certification. HCPs not providing pretravel consultation were less comfortable with traveler's diarrhea self-treatment, malaria chemoprophylaxis, altitude illness prevention, yellow fever, Japanese encephalitis, rabies, and typhoid vaccination management. The most desired topics for education were travel vaccinations (94, 46 %), travel medicine insurance (89, 43 %), and altitude illness prevention (86, 42 %). Major barriers to providing pretravel consultation were lack of clarity about reimbursement (110, 54 %), lack of insurance coverage (89, 43 %), and inability to stock travel vaccines (73, 36 %). Top interventions suggested to increase access to and awareness of pretravel consultation included primary care physician education and community outreach. Most HCPs were interested in pretravel educational opportunities, but comfort varied by experience and certification, highlighting need for targeted training, especially for primary care providers. Top barriers were insurance coverage for pretravel consultation and access to travel vaccines, underscoring critical gaps in the US healthcare system.

  PublisherDOI

• Correction: The fall—And rise—In hospital-based care for people with HIV in South Africa: 2004–2017

  PLOS Global Public Health · 2025-09-08

  erratumOpen access

  [This corrects the article DOI: 10.1371/journal.pgph.0002127.].

  PublisherOA PDFDOI

• Complexity of Adherence Challenges: Understanding Syndemic Factors Affecting HIV Treatment Adherence During Treatment Initiation in Cape Town, South Africa

  AIDS and Behavior · 2025-12-05

  articleOpen access
  PublisherOA PDFDOI

• Using Minimally Invasive Tissue Sampling and Determination of Cause of Death to Establish Etiologies of Community Respiratory Deaths Among Zambian Infants and Children

  Journal of the Pediatric Infectious Diseases Society · 2024-12-30 · 1 citations

  articleOpen access

  In low-to-middle-income countries, acute lower respiratory infection (ALRI) remains the leading infectious cause of death among infants and children under 5 years old. Case-control studies based on upper respiratory sampling have informed current understandings of ALRI etiologies; in contrast, minimally invasive tissue sampling (MITS) offers a method of directly interrogating lower respiratory tract pathogens to establish etiologic distributions. This study performed in the postmortem setting used MITS and a Determination of Cause of Death (DeCoDe) panel to elucidate the causes of fatal pneumonia in the community in Lusaka, Zambia. For deceased infants and children under age 5 years whose next-of-kin provided consent, a verbal autopsy was obtained and 6 lung tissue biopsies from each case were sent for histopathology and multiplex polymerase chain reaction testing. Subsequently, a multi-disciplinary DeCoDe panel met to review each case, determine if the child died of respiratory causes, construct a causal chain of diagnoses directly leading to the death, and determine if the death was preventable (i.e., if an identifiable intervention would have averted the death). Among 106 deaths, 49 were adjudicated as respiratory deaths, with etiologic causes including Klebsiella pneumoniae (13), Streptococcus pneumoniae (5), and Pneumocystis jirovecii (4), among others. Of note, for 21 respiratory deaths, a causative pathogen could not be identified despite clinical and histopathologic evidence of ALRI. A large majority of all deaths were considered preventable (90/106 or 85%). This study demonstrates the impact of certain respiratory pathogens through direct in situ tissue sampling with supportive pathologic data and presents a useful method of studying the etiologic distribution of fatal ALRIs in settings where many deaths occur in the community.

  PublisherOA PDFDOI

Frequent coauthors

• Davidson H. Hamer

  Boston University

  173 shared

• Matthew P. Fox

  University of the Witwatersrand

  100 shared

• Donald M. Thea

  Boston University

  84 shared

• Lin H. Chen

  Mount Auburn Hospital

  82 shared

• Christopher Gill

  65 shared

• Lawrence Mwananyanda

  Right to Care

  64 shared

• Sergio Carmona

  University of the Witwatersrand

  62 shared

• Wendy Stevens

  59 shared

Labs

• Admissions TeamPI

Education

• SD, Population and International Health

  Harvard School of Public Health

  1999

• SM, Population and International Health

  Harvard School of Public Health

  1995

• BA, International Relations

  University of California Davis

  1985