About

Dr. Ajay Sethi is a Professor of Population Health Sciences and the Faculty Director of the MPH Program at the University of Wisconsin–Madison. His research broadly focuses on infectious diseases, aiming to identify modifiable behavioral and structural factors associated with transmission, morbidity, and mortality related to infections. His work encompasses areas such as HIV/AIDS, COVID-19, healthcare-associated infections, the microbiome, and addressing public health misinformation. Dr. Sethi has been recognized for his teaching excellence with the Chancellor’s Distinguished Teaching Award in 2021. He holds a PhD in Epidemiology and an MHS in Molecular Microbiology and Immunology from the Johns Hopkins Bloomberg School of Public Health, and a BS in Physiology from the University of Maryland, College Park.

Research topics

• Medicine
• Biology
• Internal medicine
• Environmental health
• Microbiology
• Virology
• Animal science
• Immunology
• Computer Science
• Data science
• Food science
• Genetics
• Veterinary medicine
• Demography
• Gerontology
• Endocrinology

Selected publications

• Integrating Medicine and Public Health Through Health Professions Education at a School of Medicine and Public Health.

  PubMed · 2026-01-01

  editorial
  Publisher

• Self-efficacy for cancer self-management in the context of COVID-19: a cross-sectional survey study

  Supportive Care in Cancer · 2025-09-10 · 1 citations

  articleOpen access

  PURPOSE: For cancer survivors, self-efficacy is needed to manage the disease and the effects of treatment. The COVID-19 pandemic disrupted cancer-related healthcare, which may have impacted self-management self-efficacy. We investigated self-efficacy reported by cancer survivors during COVID-19, including associations with healthcare disruptions, distress, and general health. METHODS: Between 2020 and 2021, 1902 individuals aged 18-80 years with a recent cancer diagnosis completed a survey regarding the effects of COVID-19 on healthcare, self-efficacy for managing cancer and social interactions, cancer-related distress, and perceived general health. Linear and logistic models estimated odds ratios and 95% confidence intervals (CIs) between self-efficacy scores, healthcare disruptions, significant distress, and general health. RESULTS: Mean self-efficacy for managing cancer was 7.58 out of 10. Greater self-efficacy was associated with lower odds for distress (OR 0.18 [95% CI 0.13-0.26], quartile 4 vs. 1) and for worse general health (0.05 [0.03-0.09]). Participants with disruptions to cancer-related healthcare had lower self-efficacy for managing cancer compared to those without (6.62 vs. 7.09, respectively, P < 0.001) and higher odds for distress (1.70 [1.36-2.14]), but not worse general health (1.13 [0.39-1.44]). Lower self-efficacy mediated 27% of the association between healthcare disruptions and increased distress (15-47%). Associations with self-efficacy for managing social interactions trended in the same direction. CONCLUSIONS: During COVID-19, disruptions to cancer-related healthcare were associated with lower self-efficacy, increased distress, and worse general health. Psychosocial interventions designed to overcome barriers and target self-efficacy may be important for enhancing outcomes among cancer survivors experiencing disruptions in healthcare access.

  PublisherOA PDFDOI

• Clinical Profile and Outcome of Infant of Diabetic Mother in Tertiary Care Newborn Care Units

  Research Journal of Medical Sciences · 2025-01-27

  articleOpen access
  PublisherDOI

• Food insecurity modifies the association between the gut microbiome and the risk of cognitive impairment in adults

  npj Aging · 2025-06-18 · 3 citations

  articleOpen access

  This study investigated the role of food insecurity as an effect modifier between the gut microbiome, including groups of microbes (cliques), and risk of cognitive impairment (RCI). The analytical sample (n = 360) included adult participants of the Survey of the Health of Wisconsin with complete data on food insecurity, RCI, and 16S rRNA sequencing from stool samples. Microbial cliques associated with RCI were identified using an interpretable machine-learning-based algorithm. All analyses were stratified by food insecurity level, and adjusted for relevant confounders. We identified two cliques whose associations with RCI were modified by food insecurity status. The presence of the clique with either Eisenbergiella or Eubacterium was more strongly associated with RCI for the food-insecure group (β = 0.29, p < 0.0001). A clique representing the presence of Ruminococcus torques, Bacteroides, CAG-352F, and/or Eubacterium had a stronger association with RCI for the food-secure group (β = 0.1, p < 0.0001). Findings suggest food security be considered in RCI etiology.

  PublisherOA PDFDOI

• An Intervention to Reduce Occupational Health Risk from Antibiotic Resistant Pathogens Among Dairy Farm Workers

  Journal of Agricultural Safety and Health · 2025-01-01 · 1 citations

  articleOpen access

  HIGHLIGHTS: This intervention utilized the Health Belief Model and Theory of Planned Behavior to address the knowledge and social barriers that increase dairy farm workers' risk to antimicrobial-resistant infections. Dairy farm workers gained a significant increase in knowledge of the 8 desired outcomes, related to occupational health skills that reduce risks, from our intervention. Limited time was a major barrier as to why dairy farm workers felt like they could not make behavioral changes that would reduce their occupational health risk. Dairy farmworkers showed a strong likelihood of making workplace health-related behavioral changes, but their intention to change was weaker in areas of personal antibiotic stewardship. ABSTRACT: This study focused on developing and evaluating an educational intervention designed to mitigate occupational health risks associated with pathogens and antibiotic-resistant bacteria among dairy farm workers. Data collected from farms and workers as part of a larger umbrella project that focused on dairy farm antibiotic use for cows and calves were used to inform elements of the Health Belief Model and the Theory of Planned Behavior, leading to eight intervention outcomes. The intervention targeted increased knowledge and promoted behavioral changes related to worker and workplace hygiene best practices, PPE use, biosecurity, and personal antibiotic stewardship. Educational materials included instructional videos, fact sheets in English and Spanish, and supplementary printed material, including illustrated take-home points, content summaries, and posters. The intervention was conducted with 32 workers from five dairy farms, using pre- and post-intervention assessments to measure knowledge gains and behavioral intentions. Results demonstrated statistically significant increases in knowledge across all targeted outcomes (p-value ≤ .001), with most participants showing a high willingness and likelihood to implement recommended behaviors related to their workplace exposures and best practices. However, participants indicated a greater reluctance to change around issues of personal antibiotic stewardship. Time constraints were the most significant and most consistent barrier to behavior change. The study highlights the importance of ongoing research and refinement of intervention strategies to address barriers and enhance protective practices among often underserved farmworkers in agriculture. These intervention strategies contribute to improved occupational health outcomes with benefits to public health by reducing the spread of antibiotic-resistant infections to the broader population.

  PublisherOA PDFDOI

• Assessing the Impacts of Dairy Farm Antimicrobial Use on the Bovine Fecal Microbiome

  Animals · 2025-06-12 · 1 citations

  articleOpen access

  Rising rates of antimicrobial-resistant infections have prompted increased scrutiny on antimicrobial use (AMU) in livestock agriculture. Dairy farms primarily use antimicrobials to maintain animal health and welfare by treating and preventing infectious diseases. However, the impact of dairy farm AMU practices on the cattle fecal microbiome remains largely unclear, partly due to difficulties in quantifying AMU. This study leveraged quantitative AMU data from 40 large commercial dairy farms to identify farms with low (n = 4) and high (n = 4) AMU. Using 16S rRNA gene amplicon sequencing, we compared the fecal bacterial communities of dairy calves and cows (healthy, cull, sick) by both AMU designation (high/low) and by individual farm AMU, summarized by animal defined daily dose (DDD) and mg/kg. We found significant differences in beta-diversity between cattle from high- and low-AMU groups using either method and found that Corynebacterium and Clostridium abundances increased with farm AMU. Additionally, we found fecal bacterial communities differed across farms within high- and low-AMU groupings, highlighting the need to account for farm-to-farm variation when assessing AMU impacts. These findings suggest that dairy farm AMU influences the fecal microbiome and identifies specific taxa that warrant further investigation as potential reservoirs for antimicrobial resistance genes.

  PublisherOA PDFDOI

• Factors Associated With Transmission Across Three Waves of SARS‐CoV‐2 in a Prospective Community‐Based Study of Households With School‐Aged Children—Dane County, Wisconsin, 2020–2022

  Influenza and Other Respiratory Viruses · 2024-10-30

  articleOpen access1st author

  BACKGROUND: Household transmission of SARS-CoV-2 is a driver of the ongoing COVID-19 pandemic. Understanding factors that contribute to secondary infection risks (SIRs) can define changing trends and inform public health policies. METHODS: The ORegon CHild Absenteeism due to Respiratory Disease Study (ORCHARDS) prospectively monitors respiratory viruses within the Oregon School District (OSD) in southcentral Wisconsin. Households with students who had ≥ 2 respiratory symptoms were eligible and opted to participate in ORCHARDS. Between October 28, 2020, and May 16, 2022, all household members provided self-collected nasal specimens on days 0, 7, and 14 for SARS-CoV-2 detection using real-time reverse-transcription-polymerase chain reaction. We used logistic regression to investigate individual- and household-level characteristics associated with SARS-CoV-2 transmission. RESULTS: Overall, 127 households comprising 572 individuals (48% female; 52% male; 0.4% nonbinary; 77% ≥ 18 years) had at least one detection of SARS-CoV-2. The overall SIR was 47% and decreased over time (pre-Delta = 72% [95% CI: 58%-83%]; Delta = 51% [40%-63%]; and Omicron = 41% [36%-47%]). Odds of household transmission were 63% lower during the Omicron period compared with the pre-Delta period (OR = 0.36 [95% CI: 0.13-0.94] p = 0.037). Greater household density (members/bedroom) was significantly associated with household transmission during the Omicron period (OR = 6.8, [2.19-21.37] p = 0.001). Index case age, illness severity, and individual symptoms were not significantly associated with odds of household transmission. CONCLUSIONS: Greater household density was associated with a higher risk of SARS-CoV-2 transmission, but the risk declined over time with subsequent variants. Interplay between variants, prior infection, and individual/household factors may identify modifiable factors (e.g., behavior and vaccination) to reduce future transmission risk.

  PublisherOA PDFDOI

• Factors associated with transmission across three waves of SARS-COV-2 in a community-based study of households with children

  2024-11-20

  articleOpen access

  <h3>Context:</h3> Household transmission of SARS-CoV-2 is a driver of the ongoing COVID-19 pandemic. Understanding factors that contribute to secondary infection rates (SIR) can define changing trends and inform public health policies. <h3>Objective:</h3> We analyzed data from a prospective, community-based, and laboratory-supported household transmission study to determine how SIR changed over 18 months and three waves of SARS-CoV-2 variants, and which household factors may have been associated with SIR. <h3>Study Design and Analysis:</h3> The ORegon CHild Absenteeism due to Respiratory Disease Study (ORCHARDS) is a longitudinal, laboratory-supported, school-based, ARI surveillance study designed to monitor respiratory virus activity in K-12 grade schools. <h3>Setting:</h3> Oregon School District, Dane County, Wisconsin, USA, between October 28, 2020, and May 16, 2022. <h3>Population Studied:</h3> Households with students who had ≥2 respiratory symptoms were eligible and opted to participate in ORCHARDS. <h3>Intervention/Instrument:</h3> All household members provided self-collected nasal specimens on days 0, 7, and 14 for SARS-CoV-2 detection using RT-PCR. Variant was ascertained through whole genome sequencing. We used logistic regression to investigate individual- and household-level characteristics associated with SARS-CoV-2 transmission. <h3>Outcome Measures:</h3> Estimated SIR for each variant. <h3>Results:</h3> Overall, 127 households comprising 572 individuals (48% female; 52% male; 77% &gt;18 years) had at least one detection of SARS-CoV-2. The overall SIR was 47% and decreased over time (pre-Delta=72% [95%CI: 58%-83%]; Delta=51% [40%-63%]; and Omicron=41% [36%-47%]. Odds of household transmission were 63% lower during the Omicron period compared to the pre-Delta period (OR=0.36 [95%CI: 0.13-0.94] P=0.037). Greater household density (members/bedroom) was significantly associated with household transmission during the Omicron period (OR=6.8, [2.19-21.37] P=0.001). Index case age, illness severity, and individual symptoms were not significantly associated with household transmission. Eliminating households with discordant strains (n=13) of SARS-CoV-2 modestly reduced overall SIR (47 to 43%). <h3>Conclusion:</h3> Greater household density was associated with higher risk of SARS-CoV-2 transmission, but the risk declined over time with subsequent variants. Interplay between variants, prior infection, and individual/household factors may identify modifiable factors (e.g., behavior, vaccination) to reduce future transmission risk.

  PublisherOA PDFDOI

• Food Insecurity Modifies the Association Between the Gut Microbiome and the Risk of Cognitive Impairment in Adults

  Research Square · 2024-11-25 · 1 citations

  preprintOpen access
  PublisherOA PDFDOI

• Descriptive epidemiology of pathogens associated with acute respiratory infection in a study of K-12 school children

  2024-11-20

  articleOpen access

  <h3>Context:</h3> School-based outbreaks often precede increased incidence of acute respiratory infections in the greater community. <h3>Objective:</h3> We evaluated acute respiratory infections (ARI) among school-aged children in a southcentral Wisconsin school district over 8.5 consecutive years to elucidate commonly detected pathogens, their unique characteristics, and epidemiological patterns. <h3>Study Design and Analysis:</h3> The ORegon CHild Absenteeism due to Respiratory Disease Study (ORCHARDS) is a longitudinal, laboratory-supported, school-based, ARI surveillance study designed to monitor respiratory virus activity in kindergarten through 12th grade schools. <h3>Setting:</h3> Oregon School District, Dane County, Wisconsin, USA, between January 2015 and June 2023, and before and after emergence of SARS-CoV-2. <h3>Population Studied:</h3> Children aged 4—12 years meeting criteria for ARI. <h3>Intervention/Instrument:</h3> Eligible participants with ARIs provided demographic, epidemiologic, and symptom data, along with a nasal swab or oropharyngeal specimen. Multipathogen testing using reverse-transcription polymerase chain reaction (RT-PCR) was performed on all specimens for 18 respiratory viruses (including SARS-CoV-2 starting September 2019) and two atypical bacterial pathogens. <h3>Outcome Measures:</h3> Pathogen identification. <h3>Results:</h3> Between January 5, 2025, and June 9, 2023, 3,498 children participated in ORCHARDS. Pathogens were detected in 2,455 of 3,498 (70%) specimens. Rhinovirus/enteroviruses (36%), influenza viruses A/B (35%), and seasonal coronaviruses (11%) were most commonly identified in positive specimens. Rhinovirus/enteroviruses and parainfluenza viruses occurred early in the academic year, followed by seasonal coronaviruses, RSV, influenza A, influenza B, and human metapneumovirus. Students who reported their possible source of infection most often cited a family member (49.6%) or classmate (34.6%). Seasonal coronaviruses, SARS-CoV-2, influenza B virus, and rhino/enteroviruses were more common in older students (&gt;10 years of age) and RSV, parainfluenza virus, influenza A virus, human metapneumovirus, and adenoviruses were more common in younger children (&lt;10 years of age). <h3>Conclusion:</h3> Since its emergence in 2020, SARS-CoV-2 was detected year-round and with a higher median age than other pathogens. Better understanding of the etiology, presentations, and patterns of pediatric acute respiratory infections can help inform medical and public health system responses to future outbreaks.

  PublisherOA PDFDOI

Recent grants

• NIH Grant R03AA015488

  NIH · $153k · 2008

Frequent coauthors

• Nasia Safdar

  University of Wisconsin–Madison

  81 shared

• Curtis J. Donskey

  Geriatric Research Education and Clinical Center

  72 shared

• Kristen Malecki

  Society of Environmental Toxicology and Chemistry

  27 shared

• Paul E. Peppard

  University of Wisconsin Health

  24 shared

• Ashley E. Kates

  William S. Middleton Memorial Veterans Hospital

  21 shared

• Garret Suen

  University of Wisconsin–Madison

  18 shared

• Shoshannah Eggers

  University of Iowa

  16 shared

• Michelle M. Nerandzic

  Steris (United States)

  14 shared

Education

• Ph.D., Population Health Sciences

  University of Wisconsin–Madison

  2010

• M.S., Population Health Sciences

  University of Wisconsin–Madison

  2006

• B.S., Epidemiology

  University of Wisconsin–Madison

  2004

Awards & honors

• 2021 Chancellor’s Distinguished Teaching Award