About

The Parker Group at the University of California, Irvine, specializes in infectious disease epidemiology and global health. Our multidisciplinary approach integrates geographic information systems (GIS), spatial data science and spatial analysis, molecular techniques, advanced statistical modeling, demography, and anthropology. We aim to unravel the complex interactions between environmental factors and infectious disease dynamics, particularly in under-resourced and conflict-affected regions.

Research topics

• Medicine
• Environmental health
• Internal medicine
• Engineering
• Demography
• Gerontology
• Biotechnology
• Immunology
• Biology
• Genetics
• Geography

Selected publications

• Nighttime lights as a proxy for conflict intensity and infrastructure recovery in Yemen and Ukraine

  Conflict and Health · 2026-05-11

  articleOpen accessSenior author

  INTRODUCTION: Quantifying the impacts of armed conflict on civilians and infrastructure remains a major challenge, particularly where reporting is limited. Most conflict measurement tools require affected populations to report events and are limited by short time series, under-reporting, and varying methods. These tools do not capture infrastructural rebuilding, which has important health implications. Given this, we demonstrate the utility of nighttime lights (NTL) as a complementary tool for measuring conflict dynamics and infrastructure recovery with an epidemiological application. METHODS: We used monthly NASA Black Marble data to analyze NTL patterns in Yemen (2012-2022) and Ukraine (2019-2024) before and after the onset of large-scale military operations. We calculated month-specific NTL ratios relative to pre-event baselines and assessed the alignment of structural breakpoints, identified using BFAST methods, with aerial attack onset. Generalized additive models were used to measure the relationship between NTL and aerial attacks while accounting for the built environment, population, diesel price (Yemen), and spatiotemporal factors. Finally, we applied NTL to an existing model on the association between conflict, measured via air raids, and cholera in Yemen by replacing the original conflict categories with ones defined by NTL and included a variable for NTL recovery. RESULTS: Mean NTL declined by 53.3% in Yemen and 21.0% in Ukraine following conflict escalation, with detected breakpoints aligning with aerial attack onset in 85.7% of Yemeni governorates and 51.9% of Ukrainian oblasts. Generalized additive models showed that attacks were significantly associated with NTL reductions, independent of built environment factors. Incorporating NTL-based conflict measures into a cholera transmission model for Yemen produced results consistent with attack-based models and found that light recovery was associated with reduced disease risk. DISCUSSION: NTL is a viable tool for measuring conflict and can offer insights on dynamics that are not present in standard tools while avoiding many of these tools' limitations. These data have epidemiological applications and can be a proxy for important events affecting transmission dynamics. While event-based tools have vast utility, NTL can complement them with specific strengths and means of application.

  PublisherDOI

• Impact of intensive control on malaria population genomics under elimination settings in Southeast Asia

  Nature Microbiology · 2026-04-13

  articleOpen access

  The malaria elimination programme in Kayin State (Myanmar) uses malaria posts for rapid detection and treatment, together with mass drug administration in high-transmission villages, which has reduced transmission by 97%. Here we examine the impact of control on parasite genomic parameters to inform future control efforts. Using 2,270 genome-sequenced Plasmodium falciparum infections from 283 malaria posts, sampled over 58 months (2015-2020), we find that parasite effective population size decreased over the study period, but there was minimal change in artemisinin resistance allele frequency until 2020, when just one predominant genotype (carrying kelch13-R561H) remained. We observed sustained localized transmission of unique parasite genotypes revealing transmission chains and positive correlations in parasite relatedness for ≤20 km. Mass drug administration resulted in parasite founder effects, providing genomic evidence for the efficacy of this control tool. These results reveal changes in population structure driven by control and rapid shifts in allele frequency in a parasite population close to elimination.

  PublisherOA PDFDOI

• Additional file 1 of Using genomic epidemiology and geographic activity spaces to investigate tuberculosis outbreaks in Botswana

  Figshare · 2026-04-03

  articleOpen access

  Supplementary Material 1

  PublisherDOI

• Challenges and responses of malaria elimination in a high-endemic area along the Thai-Myanmar border: A health systems perspective

  PLOS Global Public Health · 2026-04-09 · 1 citations

  articleOpen access

  Despite Thailand's progress under the 1-3-7 malaria elimination framework, border districts such as Tha Song Yang in Tak Province continue to experience persistent transmission due to high population mobility, geographic constraints, and health system challenges. Understanding how local health systems respond to these pressures is critical for sustaining malaria elimination in complex border settings. This mixed-methods study applied the World Health Organization's Six Building Blocks framework to examine challenges and responses in malaria elimination in Tha Song Yang District. Qualitative data were collected through in-depth interviews with 24 key informants from district health offices, vector-borne disease units, malaria posts and clinics, hospitals, and local authorities. Quantitative data included household surveys assessing malaria-related knowledge, attitudes, and practices (n = 388), and secondary surveillance data on adherence to the 1-3-7 strategy from 2018 to 2022. Adherence to Day 1 and Day 3 activities improved steadily, reaching 96% and 100%, respectively, while Day 7 adherence declined sharply to 69% in 2022. The household survey showed high levels of malaria knowledge (75.77%) and positive attitudes toward prevention (94.59%), indicating that community awareness was strong despite ongoing transmission. Qualitative findings highlighted a surge of short-term migrants, workforce shortages, reduced domestic funding, and logistical barriers in remote areas as key constraints, while adaptive local responses-including local flexibility, committed leadership, and the use of the Malaria Information System and mobile communication platforms-helped sustain malaria control and surveillance activities. These findings demonstrate that malaria persistence in border areas is driven primarily by systemic and operational challenges rather than gaps in community awareness. Strengthening malaria elimination in similar border settings requires resilient health systems with sustained domestic financing, adaptive surveillance strategies, effective use of digital tools, and governance arrangements that account for population mobility and cross-border complexity.

  PublisherDOI

• Additional file 1 of Using genomic epidemiology and geographic activity spaces to investigate tuberculosis outbreaks in Botswana

  Figshare · 2026-04-03

  articleOpen access

  Supplementary Material 1

  PublisherDOI

• Context-specific drivers of non-regular long-lasting insecticidal net use in the Greater Mekong Subregion

  Malaria Journal · 2026-01-31

  articleOpen access

  BACKGROUND: Long-lasting insecticidal nets (LLINs) are essential for malaria prevention, yet consistent use remains suboptimal. This study assessed LLIN use and associated factors in Thailand and Myanmar across diverse transmission contexts. METHODS: We analyzed cross-sectional data from 13,459 individuals attending malaria service points in three districts in Thailand and two townships in Myanmar (2017-2024). LLIN use was categorized as daily, intermittent, or non-use. Logistic regression identified factors linked to non-regular use in each country. A directed acyclic graph (DAG) illustrated hypothesized causal pathways. RESULTS: Among 3,062 participants in Myanmar, 16.9% reported intermittent or non-use. Higher odds were observed among individuals aged 5-14 years (aOR = 1.87, 95% CI: 1.29-2.75), 15-34 years (aOR = 3.42, 95% CI: 2.07-5.67), and ≥ 35 years (aOR = 4.42, 95% CI: 2.50-7.86), Rakhine ethnicity (aOR = 3.54, 95% CI: 2.76-4.57), residence in Paletwa (aOR = 20.9, 95% CI: 5.29-109), uncertain malaria history (aOR = 8.03, 95% CI: 3.61-18.4), and Plasmodium falciparum infection (aOR = 2.87, 95% CI: 2.02-4.06). Among 10,397 participants in Thailand, 31.2% reported intermittent or non-use. Significant factors included older age (aOR = 2.73, 95% CI: 2.07-3.62 for 15-34 years), male sex (aOR = 1.73, 95% CI: 1.56-1.91), agricultural occupation (aOR = 1.42, 95% CI: 1.04-1.95), residence in Bannang Sata (aOR = 17.9, 95% CI: 14.4-22.4) or Saba Yoi (aOR = 34.4, 95% CI: 23.3-52.3), P. falciparum (aOR = 3.61, 95% CI: 1.71-7.78), P. vivax (aOR = 2.74, 95% CI: 2.38-3.17), and lower odds with uncertain malaria history (aOR = 0.49, 95% CI: 0.35-0.68). CONCLUSION: Non-regular LLIN use was common and linked to demographic, occupational, and clinical factors. Context-specific strategies are needed to improve adherence and support malaria elimination goals.

  PublisherDOI

• Refugee Health Inclusion: Legal, Geopolitical, and Economic Barriers

  International Migration · 2025-06-09 · 1 citations

  articleOpen accessSenior authorCorresponding

  ABSTRACT This commentary examines how structural constraints shape health access in refugee camps. It stems from a recent workshop on refugee health and reflects an interdisciplinary, policy‐focused dialogue. We argue that humanitarian aid alone is insufficient. Instead, long‐term, rights‐based approaches are needed. Donor dependency, legal exclusion and geopolitical dynamics undermine access to care. These challenges create artificial divides between camp and non‐camp settings. Our analysis complements a companion piece on health system design (see Tarnas et al. this issue). Together, the two pieces call for ethical, inclusive models that recognise refugee health as a global responsibility not a temporary emergency.

  PublisherOA PDFDOI

• Community acceptance of Ivermectin mass drug administration for malaria in Southern Thailand

  Scientific Reports · 2025-08-08 · 1 citations

  articleOpen access

  Thailand's goal to eliminate malaria by 2030 faces significant challenges, in part due to inadequate vector control measures. Innovative strategies, such as mass drug administration (MDA) of ivermectin, have shown promise in improving vector control efforts. This study aims to assess the factors influencing the acceptance of ivermectin MDA among residents in southern Thailand. In 2022, a cross-sectional study was conducted in three districts of Surat Thani Province, southern Thailand, where an ivermectin MDA program was planned. Quantitative data were collected through structured surveys administered to randomly selected household heads using a standardized questionnaire. Descriptive statistics and multiple logistic regression models were employed to identify factors associated with the reported acceptance of ivermectin MDA. A total of 391 participants were surveyed, with the majority (96.4%) expressing acceptance of the planned ivermectin MDA. Forest-related workers (aOR: 4.2, 95% CI: 1.1-16.1) and those who believed malaria could be eliminated from their villages (aOR: 9.1, 95% CI: 2.8-29.9) were more likely to exhibit higher levels of acceptance. However, according to programmatic records, only 59.0% of the 3,137 eligible individuals completed all three rounds of ivermectin MDA. Key barriers to participation included absence from the village for unspecified reasons and reluctance to take the drug, particularly in later rounds. There was a noticeable gap between reported acceptance and actual participation in the ivermectin MDA. Targeted efforts to engage forest-related workers are crucial to maintain high participation rates. Strengthening community engagement by emphasizing the risks and benefits of ivermectin, outlining safety measures, and raising awareness about malaria prevention and control are crucial for improving MDA uptake.

  PublisherOA PDFDOI

• Access versus utilization: determinants of insecticide-treated net non-use in Myanmar

  Malaria Journal · 2025-08-28

  articleOpen access

  BACKGROUND: Vector control has played a pivotal role in malaria control and elimination efforts, with insecticide-treated nets (ITNs) recognized as one of the most effective and widely accepted strategies. This study assessed ITN use and identified factors associated with non-use among individuals with access to ITNs in Myanmar. METHODS: Data were drawn from the nationally representative 2015-2016 Myanmar Demographic and Health Survey. Access to ITNs was defined as having at least one ITN per two household members, and ITN use as having slept under an ITN the night before the survey. Descriptive statistics and multivariable logistic regression models were conducted using the "svyset" command in STATA to account for the two-stage stratified cluster sampling design. RESULTS: Among 6,140 individuals with access to ITNs, approximately one-third (31.6%, 95% CI 28.3%-35.0%) reported not using them. Factors associated with higher odds of ITN non-use were age 15-34 years (adjusted odds ratio [aOR]: 1.31; 95% CI 1.07-1.61) and ≥ 50 years (aOR: 1.33; 95% CI 1.07-1.67), rural residence (aOR: 1.82; 95% CI 1.10-3.01), and belonging to the fourth wealth quintile, representing higher socioeconomic status (aOR: 1.74; 95% CI 1.06-2.85). CONCLUSIONS: Despite having access to ITNs at that time, a substantial proportion of individuals in Myanmar did not use them. These historical findings highlight behavioural and contextual barriers that existed before recent health system disruptions due to political unrest and COVID-19. Although present-day challenges differ, understanding past determinants of ITN non-use remains valuable for designing behaviour change communication (BCC) strategies, especially in regions where ITN distribution remains feasible.

  PublisherOA PDFDOI

• Drivers of delay in reported malaria care-seeking in Myanmar and Thailand

  Malaria Journal · 2025-12-01

  articleOpen access

  BACKGROUND: Timely malaria care-seeking and treatment is crucial to prevent severe illness and reduce onward transmission. This study assessed the reported time to care-seeking and identified its associated factors among febrile patients attending community-based malaria facilities in Myanmar and Thailand. METHODS: Longitudinal data were collected from febrile patients suspected of malaria who sought care through Village Health Volunteers in Myanmar (December 2017-June 2021) and at malaria clinics and posts in Thailand (January 2018-June 2024). Standardized case record forms in local languages were used at diagnosis. Descriptive statistics and multivariable log-logistic Accelerated Failure Time (AFT) models were used to estimate Time Ratios (TRs). RESULTS: In Myanmar (n = 2,960), the reported mean fever duration at diagnosis was 1.8 days (SD: 1.3). Longer time to care-seeking was associated with Shan ethnicity (TR: 1.48; 95% CI 1.41-1.55), other ethnicities (TR: 1.24; 95% CI 1.08-1.41), farmers (TR: 1.12; 95% CI 1.0-1.25), uncertain malaria history (TR: 1.26; 95% CI 1.09-1.47), and diagnosis with Plasmodium falciparum (TR: 1.10; 95% CI 1.02-1.19) or Plasmodium vivax (TR: 1.23; 95% CI 1.13-1.34). Shorter delays were associated with daily bed net use and diagnosis during the third or fourth quarters of the year. In Thailand (n = 15,576), the reported mean fever duration was 2.9 days (SD: 1.8). Longer delays were linked to farmers (TR: 1.07; 95% CI 1.02-1.11), pre- or primary education (TR: 1.02; 95% CI 1.00-1.04), uncertain malaria history (TR: 1.10; 95% CI 1.06-1.14), diagnosis with P. falciparum (TR: 1.27; 95% CI 1.09-1.46), P. vivax (TR: 1.20; 95% CI 1.17-1.23), or other malaria species (TR: 1.32; 95% CI 1.12-1.56), and diagnosis during the third (TR: 1.03; 95% CI 1.00-1.05) or fourth quarters of the year (TR: 1.06; 95% CI 1.04-1.09). Shorter care-seeking times were observed among non-agricultural occupations such as merchants and monks, individuals with prior malaria episodes, and occasional or daily bed net users. CONCLUSIONS: Delays in malaria care-seeking remain common in both Myanmar and Thailand. The identified risk factors, including ethnicity, occupation, malaria history, and preventive behaviours, should be considered in the design of targeted interventions to promote timely care-seeking in malaria-endemic settings.

  PublisherOA PDFDOI

Frequent coauthors

• François Nosten

  University of Oxford

  249 shared

• Jordi Landier

  Economic & Social Sciences, Health Systems & Medical Informatics

  248 shared

• Lorenz von Seidlein

  University of Oxford

  143 shared

• Arjen M. Dondorp

  Mahidol Oxford Tropical Medicine Research Unit

  141 shared

• Gilles Delmas

  Shoklo Malaria Research Unit

  128 shared

• Nicholas J. White

  124 shared

• Aung Myint Thu

  East Yangon General Hospital

  122 shared

• Khin Maung Lwin

  117 shared