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Emerging Infectious Diseases

Centers for Disease Control and Prevention (CDC)

Preprints posted in the last 30 days, ranked by how well they match Emerging Infectious Diseases's content profile, based on 103 papers previously published here. The average preprint has a 0.10% match score for this journal, so anything above that is already an above-average fit.

1
Detection of Anti-H5 Antibodies in People with Exposure to Wild Birds in Northern Canada

Wallace, H. L.; Hiebert, M.; Hunter, M.; Halbrook, M.; Harrigan, R. J.; Bogoch, I. I.; Rimoin, A. W.; Shaw, S. Y.; Larcombe, L.; Orr, P. H.; Kindrachuk, J.

2026-05-26 infectious diseases 10.64898/2026.05.24.26353994 medRxiv
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Using a commercially available H5 serology assay, we identified a 7.4% (n=5/68) anti-H5 seroreactivity rate among hunters in Northern Canada. All participants reported close contact with wild birds.

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Powassan Virus Seroprevalence in a U.S. Servicemember Population at High Risk for Tick Exposure

Tse, A. L.; Dipasqua, Z.; El Hamouche, J.; Fallon, G.; Enos, K. E.; Horowicz, G. C.; Rossen, M. J.; Chapman, W. V.; Daffin, M. N.; Kiniry, K. A.; Jankovich, A.; Choy, J. S.; Whitfield, A. R.; Bachert, B. A.; Cazares, E.; Lasso, G.; Jones, J. E.; Bateman, S. L.; Gordon, D.; Stahlman, S. L.; Herbert, A. S.; Florez, C.; Lai, J. R.; Chandran, K.; ODonovan, K. J.; Hershfield, J. R.; Miller, E. H.

2026-06-03 infectious diseases 10.64898/2026.06.02.26354611 medRxiv
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Powassan virus (POWV) is an emerging tick-borne flavivirus that can cause severe encephalitis in humans. Currently no vaccines or therapeutics are approved to treat POWV. POWV is spread by the deer tick, Ixodes scapularis, which is ubiquitous across the Northeastern United States. To better understand POWV prevalence in high-risk populations, we examined POWV seroprevalence in Cadets at United States Military Academy (USMA) in West Point, New York. Cadets at USMA, located in a heavily wooded area, are at high risk for tick exposure during outdoor military training. 1,051 serum samples from the Cadet class of 2017 were screened for POWV seropositivity using a POWV Envelope (E) DIII ELISA. A seropositivity rate of 1.3% was determined. Several ELISA-positive samples were also able to neutralize both reporter virus particles bearing the POWV E protein and authentic POWV. This study demonstrates populations at risk for tick exposure may have significant seroprevalence of POWV.

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Genomic epidemiology as a tool for understanding drivers of hepatitis A community outbreaks in Massachusetts and New Hampshire

Krasilnikova, L. A.; Bouton, L.; Brock-Fisher, T. M.; Decker, E.; Godec, M.; Thompson, Z.; Dart, E.; Gao, F.; Gladden-Young, A.; Messer, K. S.; Norville, J.; Specht, I.; Osinski, A.; Li, J.; Lones, C.; DeRuff, K. C.; Siddle, K. J.; Church, D.; Benton, C.; Hansen, K.; Bowen, H.; Bhattacharyya, S.; Epie, N.; Brown, C. M.; Madoff, L. C.; MacInnis, B. L.; Gallagher, G. R.; Smole, S.; Bean, C.; Talbot, E. A.; Burns, M.; Doucette, M.; Fortes, E.; Park, D. J.; Sabeti, P. C.; Wohl, S.

2026-05-19 infectious diseases 10.64898/2026.05.14.26352933 medRxiv
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Despite the existence of an effective vaccine, the United States continues to experience outbreaks of hepatitis A, including in Massachusetts (MA) and New Hampshire (NH) in 2018 and again in MA in 2023. To clarify the relationship between these outbreaks and better understand their drivers, we generated hepatitis A virus whole genome sequences from reported cases and analyzed them using open-source genotyping tools developed and released as part of this study. We found that the 2018 and 2023 outbreaks were caused by distinct viral strains, despite affecting individuals with similar demographic characteristics and reported risk factors. Detailed analysis of genomic and epidemiologic data further resolved transmission patterns within and across outbreaks, showing that experiencing homelessness and prior use of drugs were associated with increased transmission while also revealing transmission between individuals with and without these risk factors, as well as spread across state borders. Together, these findings demonstrate the value of broadly accessible genomic tools for understanding hepatitis A outbreaks and illustrate how whole genome analysis can complement epidemiological investigation by resolving transmission patterns and outbreak drivers that can inform public health interventions.

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Data gaps of international databases on HPAI H5 in wildlife in the Americas: implications for surveillance, research, and conservation

Vanstreels, R. E. T.; Uhart, M. M.

2026-06-01 microbiology 10.64898/2026.05.30.728949 medRxiv
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Global efforts to prevent and mitigate the impacts of high pathogenicity avian influenza (HPAI) H5 on domestic animals, humans, and wildlife rely on timely and transparent information that is both accurate and interpretable across countries and sectors. International epidemiological and genomic databases, such as the World Animal Health Information System (WAHIS), the Global Animal Disease Information System (EMPRES-i+), the Global Initiative on Sharing All Influenza Data (GISAID), and the National Center for Technological Bioinformation Virus Portal (NCBI) provide essential information for surveillance, research, and decision-making. To evaluate how well these resources capture recent wildlife impacts, we consolidated information from these databases and complementary public sources including government reports, scientific literature, and news articles, on wildlife mortality associated with HPAI H5 in the Americas from November 2021 to July 2024. The consolidated dataset comprised 615,883 wild birds (287 spp.) and 63,409 wild mammals (39 spp.). In comparison, WAHIS represented 16,902 wild birds (261 spp.) and 6,323 wild mammals (31 spp.) while EMPRES-i+ captured a substantially smaller portion of affected host diversity for both wild birds (105 spp.) and wild mammals (27 spp.). Genomic databases (GISAID and NCBI) represented 7,027 whole genome equivalents of H5 viruses from wild birds (175 spp.) and 371 from wild mammals (26 spp.). These discrepancies indicate that international databases, while essential, provide an incomplete picture of HPAI impacts on wildlife, with significant geographic and taxonomic asymmetries attributable to differences in surveillance capacity, reporting practices, sequencing effort, and data-sharing pathways. Studies and management strategies relying on these resources without complementary validation may therefore mistake data gaps for real-world epidemiological patterns. Strengthening data reporting standards, improving validation procedures, and integrating international databases with national reports, scientific publications, and other sources will enhance the reliability of epidemiological analyses and support more effective One Health surveillance, risk assessment, and conservation action. Author summaryHigh pathogenicity avian influenza (HPAI) H5 viruses, often called bird flu viruses, can cause severe disease in birds and mammals, including humans. Because of their relevance for human health, livestock production, and wildlife conservation, international databases were established to share information on when and where these viruses are detected, which species are affected, and what virus strains are found. These databases are essential tools for governments, scientists, and conservation practitioners working to track outbreaks, understand how these viruses spread and evolve, and guide surveillance and response. In this study, we compiled and compared information on recent HPAI H5 events in wildlife in the Americas available in international databases with information from other public sources, including reports from governments, scientific literature, and news articles. We found important discrepancies in how countries and species affected were represented across sources. As a result, international databases might not fully capture the actual distribution or conservation impact of HPAI H5 on wildlife. Our findings also show why decision-makers and scientists should interpret database-derived patterns carefully. We provide recommendations to improve international databases to address these gaps and better inform One Health risk assessment and wildlife conservation actions.

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Widespread circulation of West Nile and Usutu viruses in sedentary and migratory avifauna: A Two-Year Study (2024-2025) of active surveillance in South of France

Beaubaton, R.; Revel, J.; Pigeyre, L.; Lepeule, A.; Joly, J.; de Franceschi, C.; Charmantier, A.; Vollot, B.; Simonin, Y.

2026-05-21 microbiology 10.64898/2026.05.21.726855 medRxiv
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West Nile virus (WNV) and Usutu virus (USUV) are neurotropic Orthoflaviviruses sharing a similar enzootic transmission cycle primarily involving Culex pipiens mosquitoes as vectors and birds as amplifying hosts. First identified in Africa, both viruses established endemicity across Europe over the past two decades, most likely introduced and spread by migratory bird species along Mediterranean flyways. In avian species, infection outcomes range from subclinical to fatal neuroinvasive disease, varying by viral strain, host immunity, and species susceptibility. Southern France emerges as a key hotspot for the circulation of these viruses, supported by diverse avian habitats conducive to year-round viral maintenance. This study investigated the prevalence of WNV and USUV in more than 2500 sedentary and migratory wild birds from these regions during 2024-2025 using molecular surveillance. Samples were collected using mist net and bird boxes, across multiple passerine and non-passerine taxa, spanning wetlands, urban fringes, and agricultural zones. Our analyses revealed widespread viral circulation across diverse species, mainly among passerines such as great tits, house sparrows, and barn swallows with USUV detected at higher rates than WNV in both study years. Overall prevalence was markedly higher in 2024 than in 2025, potentially reflecting climatic or ecological drivers. Migratory individuals likely seed viral introductions during seasonal passages, whereas resident populations sustain local enzootic cycles, facilitating overwintering persistence. These results highlight the pivotal role of mixed avifauna in arbovirus dynamics within Mediterranean Europe and emphasize the necessity for integrated, year-round surveillance targeting high-risk species and habitats. Enhanced monitoring will aid in predicting spillover risks and informing vector control strategies to mitigate zoonotic threats.

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Sustained Specific EBOV GP Immunogenicity Five-Years Post-Vaccination: Longitudinal Results from North Kivu and Equateur, Democratic Republic of the Congo

Merritt, S.; Hoff, N. A.; Mukadi, P. K.; Kompany, J. P.; Halbrook, M.; Tambu, M.; Beya, M.; Kalengi, H.; Etuk, V.; Wong, T. A.; Muyembe, J.-J. T.; Kelly, J. D.; Kaba, D.; Hensley, L.; Lehrer, A. T.; Kindrachuk, J.; Mbala-Kingebeni, P.; Rimoin, A. W.

2026-05-22 infectious diseases 10.64898/2026.05.19.26353493 medRxiv
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Ebola virus disease (EVD), caused by the Ebola virus (EBOV), is characterized by high morbidity and mortality, with 16 distinct EVD outbreaks reported in the Democratic Republic of the Congo (DRC), alone. As part of the formal response to the 2018 outbreaks in Equateur and North Kivu provinces, a recombinant vesicular stomatitis virus-Zaire Ebolavirus envelope glycoprotein vaccine (rVSV-ZEBOV-GP) vaccine was deployed under emergency use. While clinical trials have evaluated vaccine safety and efficacy, there is a paucity of real-world data documenting antibody durability for longer periods post-vaccination. Here, we present serologic data from 1081 individuals in Beni, North Kivu (n = 599) and Mbandaka, Equateur (n = 482) who were vaccinated during the outbreaks--with samples from baseline up to five-years following vaccination. Using a multiplexed immunoassay, we show sustained anti-EBOV GP reactivity: at year-5 collection, 72% of individuals naive at time of vaccination remained seroreactive to EBOV GP. Stratifying by site, antibody titers remained significantly elevated after baseline across all post-vaccination timepoints in both linear and logistic mixed-effects models. Pre-existing EBOV GP reactivity at baseline was the strongest independent predictor of antibody response in Mbandaka, associated with higher titers and greater odds of seropositivity (OR = 3.87, 95% CI: 2.50-6.01, p-value < 0.001), consistent with a boosting effect among previously exposed individuals. However, this was not replicated in Beni (OR: 0.66, 95% CI: 0.27-1.58, p-value = 0.348). In Mbandaka, among those recipients who reported receiving a booster dose, the odds of seroreactivity were 12.75-fold (p-value < 0.001) and 3.68-fold higher (p-value = 0.04) at 4.2 and 5-years post-vaccination, respectively, in comparison to odds of reactivity at three weeks following administration of the initial dose. Occupational groups with zoonotic or community-level exposure had trending lower odds of seroreactivity relative to healthcare workers, most consistently in Beni. Ultimately, these data indicate that five years following administration of the rVSV-ZEBOV-GP vaccine, most vaccinated individuals retain detectable anti-EBOV GP antibodies. While correlates of protection for EVD are not well established, sustained IgG seroreactivity to EBOV GP may serve as a marker for future understandings of the durability of and variation in immune responses to this high-consequence pathogen.

7
Pooled testing for SARS-CoV-2 surveillance in schools: real-world evaluation of transmission control, testing resources, and educational disruption

Colosi, E.; Calmon, L.; Fässli, M.; Koch, K.; Bielicki, J. A.; Colizza, V.

2026-06-04 infectious diseases 10.64898/2026.06.03.26354821 medRxiv
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Pooled testing programs were introduced during the COVID-19 pandemic to expand surveillance capacity while preserving testing resources, but evidence on their epidemiological impact in schools under real-world conditions remains limited. We analyzed data from the pooled testing program implemented in public primary schools of the canton of Basel-Landschaft, Switzerland, during the Fall-Winter 2021 Delta wave. We used an agent-based transmission model informed by pooled and individual testing results, school characteristics, contact networks, and community incidence. The model was fitted to pooled positivity ratios in four clusters of administrative areas with similar epidemic trajectories. We compared pooled testing with alternative protocols in terms of school transmission, testing volume, and student-days lost. During the study period, pooled testing was offered to 21'187 students across 62 public primary schools, with high and stable participation across clusters (mean 71-79%). The fitted model reproduced observed pool positivity trends well. Compared with pooled testing, reactive class closure, reactive screening, and symptomatic testing were associated with higher in-school transmission, with excess ranging from 50% to 87%, 63% to 104%, and 72% to 133% across clusters. Weekly individual screening achieved similar reductions in transmission but required 15-25 times more tests. Relaxing class closure after depooling substantially reduced student-days lost without increasing transmission. Under real-world conditions, pooled testing provided an effective and resource-efficient strategy to reduce SARS-CoV-2 transmission in primary schools. Combining early detection of asymptomatic infections with low testing demands, pooled testing offers a scalable approach to school surveillance and control for pandemic response in educational settings.

8
Reduction of Microbial Diversity During Artisanal Fermentation and Detection of Multidrug-Resistant Salmonella in Commercially Imported Beef in Puerto Rico

Carmona-Ortiz, M.; Cartagena-Teruel, J. A.; Maldonado-Maldonado, A. N.; Martinez-Pacheco, L. G.; Ortiz-Cartagena, L. G.; Rodriguez-Plata, G. L.; Santiago-Collazo, G.

2026-06-03 public and global health 10.64898/2026.06.01.26354615 medRxiv
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Artisanally produced embutidos are a culturally significant fermented meat product widely consumed in Puerto Rico, yet their microbiological safety remains largely uncharacterized. This preliminary study evaluated the effect of artisanal fermentation on microbial diversity and assessed the presence of potentially pathogenic and antimicrobial-resistant Proteobacteriain locally produced embutidos. Raw pork (locally sourced) and beef (commercially imported) were obtained from retail supermarkets and processed at a small-scale production facility under standard artisanal conditions. Surface sampling using RODAC contact plates on TSA, MAC, and SDA media was performed before and after fermentation. Fermentation reduced overall microbial diversity in both meat types. Two Gram-negative isolates recovered from pre-fermentation samples were characterized using selective and differential media (MAC, MSA, EMB) and the IMViC biochemical test series. A Salmonella specie was presumptively identified from imported beef, and an Enterobacter species from locally sourced pork. Kirby-Bauer disk diffusion testing revealed that the Salmonella isolate was resistant to five antibiotics (ampicillin, methicillin, penicillin, streptomycin, tetracycline) and showed intermediate susceptibility to chloramphenicol and gentamicin. The Enterobacter isolate was resistant to five antibiotics (ampicillin, methicillin, penicillin, streptomycin, tetracycline) and showed intermediate susceptibility to chloramphenicol and gentamicin. Both isolates met MDR criteria, highlighting the need for enhanced microbiological oversight of artisanally produced embutidos in Puerto Rico.

9
Detection of a Vibrio paracholerae Case in a Diarrheal Disease Outbreak in Costa Rica

Cordero-Laurent, E.; Calderon-Osorno, M.; Godinez-Rojas, A.; Blanco-Arguedas, J.; Barquero-Urena, G.; Umana-Valverde, E.; Oropeza-Barrios, G.; Chanto-Chacon, G.; Lee, C. C.; Duarte-Martinez, F. J.

2026-05-12 infectious diseases 10.64898/2026.05.07.26352676 medRxiv
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First documented detection of Vibrio paracholerae in a Costa Rican foodborne outbreak. Genomic analysis confirmed species identity, revealing limitations of conventional PCR and MALDI methods. Findings underscore the need for genomic surveillance to accurately characterize emerging enteropathogens and support public health systems.

10
Heterogeneity in Mycobacterium tuberculosis immunoreactivity in young children in Blantyre, Malawi: a community-based survey

Rickman, H. M.; Phiri, M. D.; Mbale, H.; Feasey, H. R.; Nliwasa, M.; Chagaluka, G.; Seddon, J. A.; Mwandumba, H. C.; Horton, K. C.; Henrion, M. Y.; Mwenyenkulu, T.; Mbendera, K. N.; Nightingal, E. S.; Corbett, E. L.; MacPherson, P.

2026-05-21 infectious diseases 10.64898/2026.05.21.26349011 medRxiv
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Background: As tuberculosis (TB) incidence declines, transmission increasingly concentrates into vulnerable populations. There is an urgent need for affordable surveillance strategies to monitor trends, identify high-risk groups and target interventions. Mycobacterium tuberculosis (Mtb) immunoreactivity surveys indirectly detect transmission and therefore undiagnosed infectious disease. Methods: We conducted a cross-sectional community-based interferon-gamma release assay (IGRA) survey in children aged 1-4 years in Blantyre, Malawi. Community-representative participants were recruited using novel convenience sampling in health facilities alongside random household sampling, and tested for Mtb immunoreactivity using QFT-Plus IGRA. We constructed hierarchical Bayesian logistic regression models for IGRA positivity, with neighbourhood-level random effects. Findings: Of 1,545 participants, 102 (6.6%) had a positive IGRA: an annual risk of Mtb infection (ARTI) of 2.7% (95% CrI 2.2-3.2%). Immunoreactivity was higher in the poorest third of households (8.7% vs 4.9%; adjusted odds ratio: 1.88, 95% CrI 1.08-3.01) compared to the richest, but was not associated with HIV exposure, malnutrition or reported household TB exposure. There was substantial between-neighbourhood heterogeneity (ARTI range 1.1-4.1%). There was no association between neighbourhood-level TB case notifications and ARTI. Interpretation: An innovative convenience sampling approach identified a high burden and substantial spatial variation of recent TB transmission, which did not correspond to case notification rates. This strategy could support identification of high-risk populations, monitoring of trends and targeted public health interventions.

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Undetected isoniazid resistance leads to rifampin-resistant tuberculosis

Spies, R.; Hanh, N. H.; Phu, P. T.; Lan, L. K.; Lan, K.; Hue, N. N.; Quang, N. L.; Thu, D. D. A.; Huong, N. T. L.; Thao, T. L. T. N.; Tram, T. T. B.; Ha, V. T. N.; Ha, D. T. M.; Hai, N. P.; Thuan, N. H.; Quy, T. T. K.; Lan, N. H.; Dreyer, V.; Niemann, S.; Crook, D.; Van, L. H.; Thwaites, G.; Thuong, N. T. T.; Choisy, M.; Watson, J.; Walker, T.

2026-05-24 infectious diseases 10.64898/2026.05.22.26353840 medRxiv
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Background: Isoniazid resistance is the most common form of drug-resistant tuberculosis (TB) globally. However, WHO-recommended molecular tests available to most TB patients worldwide detect rifampin resistance only, risking under-treatment of isoniazid-resistant, rifampin-susceptible TB (HR-TB) and subsequent emergence of rifampin resistance. Methods: This prospective study (2020-2024) aimed to collect and archive sputum specimens from all adults diagnosed with rifampin-susceptible pulmonary TB in Ho Chi Minh City, Vietnam. Cases were participants who developed rifampin-resistant recurrence; controls had rifampin-susceptible recurrence or no recurrence. Whole-genome sequencing of paired isolates distinguished acquired rifampin resistance from reinfection. The effect of pre-existing isoniazid resistance on rifampin resistance acquisition was estimated using inverse probability of treatment weighting, and the projected epidemiological impact of routine HR-TB testing was modelled. Results: 42,843 people were diagnosed with TB during the study period, from whom we archived 33,843 sputum samples. We enrolled 1,241 participants, 873 (70.4%) of whom had analysable data. 51/873 (5.8%) acquired rifampin resistance, of whom 49/51 (96.1%) had undetected isoniazid resistance. The weighted risk of acquired rifampin resistance was 2.98% (95% CI 2.08-4.50) with undetected isoniazid resistance, versus 0.03% (0.00-0.08) without (risk ratio105.42 (33.43-309.69)). Modelling projected that universal HR-TB diagnosis and treatment would reduce RR-TB incidence by 46% (35-61) over 10 years in Vietnam, with reductions of 26% (12-43) projected even where HR-TB prevalence was as low as 5%. Conclusions: Undetected, under-treated HR-TB confers a 100 fold increased risk of acquiring rifampin resistance. Routine isoniazid susceptibility testing combined with effective HR-TB treatment could substantially reduce the burden of RR-TB.

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Prevalence and Factors Associated with Methicillin-Resistant Staphylococcus Nasal Carriage Among People Living with HIV at Kiruddu National Referral Hospital, Kampala, Uganda

Babirye, J. A.; Bwanga, F.; Nakalega, R.; Mawanda, D.; Kugonza, C. D.; Namiiro, S. M.; Nakiganda, M.; Semitala, F.; Byakika-Kibwika, P.

2026-05-27 infectious diseases 10.64898/2026.05.26.26354086 medRxiv
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Methicillin-resistant Staphylococcus (MRS) infections are a significant public health concern. Anterior nares serve as a major reservoir and source of spread of MRS ssp. People living with HIV (PLWHIV) tend to be at higher risk of colonisation with MRS organisms due to frequent healthcare exposure. We assessed the prevalence of MRS nasal carriage and associated factors among PLWHIV at the HIV clinic of Kiruddu National Referral Hospital, Kampala, Uganda, from May to July 2024. Nasal swabs from 256 PLWHIV were cultured, and microbiological isolation was performed at MBN Clinical Laboratories. Prevalence was calculated as proportions, and logistic regression identified associations with clinical and socio-demographic factors (p < 0.05). Of 256 participants, 163 (63.7%) carried Staphylococcus, with 82 (32%) identified as MRS carriers (8.9% MRSA, 23% MRCoNS). Frequent hospital visits ([&ge;]3) (adjusted incidence risk ratio [A-IRR] = 1.18 x 107, p < 0.001), second-line antiretroviral therapy (ART) (A-IRR = 3.82, p = 0.041), and unsuppressed viral load (>1000 copies/mL) (adjusted odds ratio [AOR] = 11.3, 95% CI: 2.11-60.58, p = 0.005) were significantly associated with MRS carriage. Mask-wearing was protective against MRCoNS (A-IRR = 1.66, 95% CI: 1.06-2.58, p = 0.026). MRS isolates exhibited high resistance to erythromycin (81.7%) and trimethoprim-sulfamethoxazole (79.3%), but susceptibility to linezolid (93.9%). MRS nasal carriage is prevalent among PLWHIV. Individuals with frequent health care contact and those on second-line ART regimens are more susceptible to MRS colonization, while individuals who wear face masks and those with an undetectable HIV viral load are less susceptible. Antimicrobial Resistance (AMR) surveillance within HIV programs, enhanced infection control, ART adherence, and targeted screening for high-risk groups are critical to mitigate colonization.

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International risk of secondary hantavirus clusters following MV Hondius outbreak

Wang, B.; Lorenzetti, E.; Parino, F.; Colizza, V.; Valdano, E.

2026-05-22 public and global health 10.64898/2026.05.21.26353570 medRxiv
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The multinational Andes virus outbreak linked to the MV Hondius has exposed contacts across several countries, but the absence of further confirmed cases remains difficult to interpret given the long incubation period. We estimate the probability that secondary clusters may emerge using a stratified branching-process model parameterized with country-level tracing and isolation indicators. The risk of sustained spread is low, but secondary clusters remain plausible under imperfect isolation or pre-symptomatic transmission. These results support coordinated contact tracing and effective isolation while exposed contacts remain within the risk window.

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A snapshot of the UK blood donor plasma virome: a retrospective cross-sectional cohort study

Kean, K.; Mayne, R. M.; Reid, K.; Secret, S.; Singleton, B. K.; Rockett, R. J.; Rajendra, P.; Harvala, H.; Breuer, J.; Ansari, M. A.; Lythgoe, K.; Simmonds, P.; Golubchik, T.

2026-05-22 public and global health 10.64898/2026.05.20.26353651 medRxiv
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Estimates of population prevalence and genetic diversity of bloodborne viruses in healthy humans are essential to support population-scale monitoring for transfusion transmission risk. In the UK and globally, blood donations are routinely screened for a limited number of high-consequence pathogens, but the full composition of the plasma virome remains to be characterised. Using a novel quantitative targeted metagenomics sequencing approach, we analysed previously unscreened plasma donations collected by NHS Blood and Transplant in England for all major pathogenic and known commensal human bloodborne viruses, and quantified their viral burden. Here we show that in a representative sample of 5,064 UK blood donors in pools of 24 collected over a one-month period, the virome was dominated by a small number of largely persistent species, representing ~11% (12/106) of previously identified human bloodborne viruses. Anelloviruses (TTV, TTMV and TTMDV) was detected in 89.0% of pools, albeit at low read count inconsistent with measured anellovirus viral loads. In contrast, human pegivirus type 1 (HPgV-1), had estimated population prevalence of 3.7% (95% CI 3.0-4.4%), with high read count and complete genome recovery in around one half of positive pools, consistent with high titre in plasma. Estimated prevalences for less common detections included one species of gemykibovirus (0.12%), hepatitis C virus (genotype 1a, 0.04%) and various polyomaviruses and herpesviruses between 0.04% (parvovirus 4, BK polyomavirus) and 0.41% (human herpesvirus 6). Phylogenetic analyses revealed mixed TTV, TTMV and TTMDV populations and almost exclusively genotype 2 HPgV-1, consistent with known genotype distributions in Europe. Our results provide a baseline for describing the healthy plasma virome in UK blood donors.

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Outbreak of H9N2 avian influenza viruses in lesser rhea in Peru, June-July 2025

Garcia-Glaessner, A.; Crespo-Bellido, A.; Munoz-Saavedra, B.; Juarez, D.; Barrera, P.; Salmon-Mulanovich, G.; Checahuari-Jarata, S. E.; Cruz, D.; Huisa-Balcon, D. X.; Idme, G.; Nelson, M. L.; Lescano, J.; Leguia, M.

2026-05-13 evolutionary biology 10.64898/2026.05.08.723762 medRxiv
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Avian influenza viruses (AIVs) are endemic in the Americas and responsible for outbreaks in both domestic and wild birds that occasionally spill over into humans. We report the first known outbreak of AIV H9N2 in lesser rhea (Rhea pennata), also known as Darwins rhea, in the region of Puno-Peru. The animals in this study lived in an isolated conservation center located in remote highlands above 4,000 m.a.s.l. Between June and July 2025, a total of 46/92 animals were recorded sick, with symptoms including greenish diarrhea (100%), hyporexia (24%), dyspnea (76%), nasal discharge (42%), drowsiness (18%) and isolation from the flock (73%), and 94% later died. Gross pathology exams revealed septicemia characterized by severe hepatitis, pneumonia, tracheitis, enteritis, and encephalitis. Swab and necropsy samples tested positive for Influenza A by PCR and were later identified as H9N2 through whole genome sequencing. We generated complete H9N2 genomes for two individuals. No additional pathogens were found. Phylogenetic analysis across all eight segments revealed that the viruses were low pathogenicity H9N2 AIV strains of North American origin, which indicated this outbreak was a new introduction of the virus into South America. We also performed a comparative mutational analysis and identified multiple mutations previously associated with mammalian host adaptation, increased virulence, increased pathogenicity, and increased virus binding to 2-6 receptors, which may explain the high mortality rates observed despite the supposedly low pathogenicity of the strain. We also identified novel mutations specific to rhea viruses that will need to be experimentally validated. This is the first report of a natural H9N2 systemic infection in an avian host, highlighting a need for increased surveillance efforts for zoonotic influenza viruses with pandemic potential. Author SummaryAvian influenza viruses (AIVs) are endemic in the Americas and cause more than 7,600 infections annually in domestic and wild birds worldwide each year. We report detection of AIV H9N2 in lesser rhea during an outbreak that occurred in June-July 2025 in the Andean highlands of Puno in Peru. Multiple sick animals were reported with symptoms of respiratory and gastrointestinal disease and 94% of them later died. Samples collected tested positive for Influenza A and they were subtyped as H9N2 of low pathogenic origin from North America. This is the third time H9N2 enters South America from North America, presumably through wild birds, some of which migrate along the Pacific Flyway. Comparison with other H9N2 sequences revealed a total of 44 mutations of interest that may explain the elevated death rates observed. Surveillance in wild birds remains patchy at best and needs to be strengthened in order to prevent spillover events into other animals, including humans.

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Genomic epidemiology and transmission dynamics of plasmids carrying New Delhi metallo-β-lactamase (blaNDM) at a single hospital system over five years

Raabe, N. J.; Mills, E. J.; Bapat, S.; Griffith, M. P.; Shutt, K.; Waggle, K. D.; Sundermann, A. J.; Shields, R. K.; Pless, L.; Snyder, G. M.; Harrison, L. H.; Van Tyne, D.

2026-05-18 infectious diseases 10.64898/2026.05.14.26353212 medRxiv
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Background: Conjugative plasmids encoding New Delhi metallo-beta-lactamase (blaNDM) pose a threat for the spread of carbapenem resistance among healthcare acquired pathogens. Plasmid-associated outbreaks of blaNDM-producing bacteria can involve multiple bacterial species and persist over long time periods, making their detection and control difficult. We systematically studied the genomic epidemiology of blaNDM-encoding plasmids detected within a single hospital system over a five-year period. Methods: blaNDM-producing isolates were collected from clinical cultures as part of the Enhanced Detection System for Healthcare-Associated Transmission (EDS-HAT) genomic sequencing active surveillance program, or during infection prevention and control (IP&C) investigations. Isolates were identified as blaNDM producers by polymerase chain reaction (PCR); the presence of plasmid-encoded blaNDM genes was confirmed by sequencing on both Illumina and Oxford Nanopore platforms. Plasmids were clustered using Pling and bacterial relatedness of host isolates was evaluated with split kmer analysis. Electronic health record data were used to identify shared unit-level spatiotemporal exposures and epidemiologic links within both plasmid and host clusters. Results: We identified 61 blaNDM-producing isolates collected from 54 patients sampled between November 2020 and July 2025. Isolates belonged to 15 Enterobacterales species; Enterobacter hormaechei was the most frequently sampled species (n=23, 37%), and blaNDM-5 was the most frequently observed blaNDM allele (n=36, 59%). We observed six clusters of genetically similar blaNDM-encoding plasmids each containing 2-28 isolates, and eight singleton plasmids. The two largest plasmid clusters consisted of a highly conserved 46 kb IncX3 family blaNDM-5-encoding plasmid (n=28 plasmids, 9 species) and a more variable 98-201 kb IncC family blaNDM-1-encoding plasmid (n=12 plasmids, 6 species). Epidemiologic investigation paired with whole genome sequencing identified spatiotemporal associations between shared patient exposures and putative plasmid and bacterial transmission clusters, suggesting that unit-level exposures contribute to plasmid dissemination. Finally, analysis of publicly available sequences showed that the most prevalent plasmids detected, IncX3(blaNDM-5) and IncC(blaNDM-1), also demonstrated high global prevalence. Conclusions: This study demonstrates the diversity of blaNDM carrying plasmids within a single hospital system and their capacity to cause prolonged, multispecies outbreaks. Integrating whole genome sequencing with epidemiologic data identified unit-level spatiotemporal overlap as a likely contributor to plasmid dissemination in the hospital.

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Telomere-to-telomere, accurate, and gapless genome assembly (TTAGGA) of the Korean Jindo dog with a single-contig Y chromosome

Choi, H.; Kim, J.-S.; Kwon, Y.; Park, S.; Jeon, S.; Bhak, J.; Shin, D.; Choi, Y.; An, K.; Ryu, D.-Y.; Paek, W. K.; Park, D.; Kim, J.; Sinding, M.-H. S.; Choe, Y.; Hyun, B.-R.; Lee, S.-k.; Bhak, J.

2026-05-20 genomics 10.64898/2026.05.17.725804 medRxiv
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Complete canine reference genomes are essential for studies of structural variation, sex-chromosome evolution, and breed-specific architecture, yet existing references remain incomplete on the Y chromosome and retain internal gaps across multiple chromosomes. Here, we introduce TTAGGA (Telomere-to-Telomere, Accurate, Gapless Genome Assembly), a stricter completeness standard requiring chromosomes assembled end-to-end with zero internal gaps and Merqury consensus QV [&ge;] 50, and present Jindo1-G-TTAGGA, the first canine assembly to meet this standard, achieved under a stringent QV [&ge;] 60 threshold. From 813 Gb ([~]340x coverage) of multi-platform data (PacBio HiFi [~]150x, ONT ultra-long [~]103x, parental Illumina [~]40x per parent) generated from a male Korean Jindo dog, trio binning with hifiasm produced two haplotype-resolved assemblies of 2,441.6 Mb (Hap1, maternal, chrX-carrying) and 2,340.5 Mb (Hap2, paternal, chrY-carrying). Both haplotypes are gap-free at every internal position, with canonical telomeric repeats verified at both ends of all 39 chromosomes (tidk), Merqury consensus QV of 78.0 (Hap1) and 76.8 (Hap2), trio switch-error rates below 0.13%, BUSCO completeness of 99.3% (Hap1) and 96.4% (Hap2; the lower value reflects absent X-linked orthologues in the Y-bearing haplotype), and Genome Continuity Index values of 98.2 (Hap1) and 94.7 (Hap2). Hap2 carries a single 21,255,890 bp gap-free Y chromosome with TTAGGG telomeric repeats at the q-arm terminus and an acrocentric satellite-rich p-arm, representing a 5.4-fold increase over the 3.94 Mb chrY of ROS_Cfam_1.0 and adding approximately 14 Mb of newly resolved Y-linked sequence; this corresponds to roughly 79% of the cytogenetically estimated 27 Mb full-length canine chrY. Jindo1-G-TTAGGA provides a chromosome-scale, haplotype-resolved, gap-free canine reference for studies of canine structural variation, sex-chromosome evolution, and canid phylogenomics.

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Limitations of cross-border containment strategies for Bundibugyo ebolavirus

Middleton, C.; Larremore, D.

2026-06-08 epidemiology 10.64898/2026.06.04.26354820 medRxiv
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An ongoing outbreak of Bundibugyo virus disease (BVD) in the Democratic Republic of the Congo was deemed a public health emergency of international concern in May 2026. To prevent cross-border importation, many countries, including the United States, Canada, India, Thailand, and Kenya have already proposed containment strategies, and others are likely to follow suit. How well (or poorly) are screening and quarantine containment measures are likely to work? We leverage established epidemiological theory and develop a mathematical model of traveler screening and post-arrival quarantine for BVD to answer this question. We find that traveler screening via symptom screening or molecular testing will miss the majority of infected travelers, and should be complemented by post-arrival quarantine and monitoring of sufficient duration to detect those with long incubation periods. Our findings underscore the limitations of border screening and the importance of complementary measures like post-arrival quarantine to prevent local importation of BVD.

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TRENDS-Thai: decadal trends of dengue, chikungunya, and hand, foot, and mouth disease in Thailand (2016-2025): a multi-disease time-series analysis of COVID-19 disruption

Pongpirul, W.; Ahmed, M. M.; Pongpirul, K.

2026-05-24 infectious diseases 10.64898/2026.05.21.26353796 medRxiv
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Introduction: Dengue, chikungunya, and hand, foot, and mouth disease (HFMD) are priority notifiable infections in Thailand. Whether vector-borne and contact-mediated diseases responded differently to the coronavirus disease 2019 pandemic has not been quantified within a unified national surveillance framework over an extended period. Methods: We conducted an ecological interrupted time-series analysis using weekly province-level notifiable disease surveillance data from epidemiological week 1 of 2016 to week 53 of 2025 across all 77 Thai provinces. Incidence per 100,000 population was calculated using year-specific civil registration population denominators. Segmented quasi-Poisson regression with two Fourier harmonics for annual seasonality was fitted, with the primary pandemic onset defined as week 1 of 2020 and two alternative onset definitions prespecified for sensitivity analysis. Results: The analysis included 40,579 province-week observations across 527 epidemiological weeks, comprising 790,263 dengue, 32,265 chikungunya, and 713,822 HFMD cases nationally. Immediate incidence rate ratios at pandemic onset were 0.39, 0.54, and 0.51 for dengue, chikungunya, and HFMD, respectively. Sustained post-onset trends diverged across diseases, with declining trajectories for the two vector-borne infections and a positive post-onset slope for hand, foot, and mouth disease. Dengue rebounded above pre-pandemic levels by 2023, chikungunya remained quiescent through 2025, and HFMD exceeded its pre-pandemic baseline by approximately 26%. Conclusion: Vector-borne and contact-mediated diseases in Thailand followed sharply contrasting decadal trajectories that tracked the transmission ecologies of each pathogen. These findings support transmission-mode-specific pandemic-resilient surveillance, accelerated arboviral and enteroviral vaccine deployment, and integrated vector management.

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Ticks and tickborne diseases in the upper Midwestern United States: role for citizen science in assessing exposure risk

Linz, A. M.; Marcis, C.; Payant, C.; Donnerbauer, L.; Donnerbauer, A.; Gruenling, E.; Boese, K.; Heuer, G.; Boehm, A.; Uelmen, J. A.; Fritsche, T. R.; Meece, J. K.

2026-05-15 microbiology 10.64898/2026.05.14.724901 medRxiv
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Tickborne diseases are a significant burden in many parts of the world. In the upper Midwestern United States, Lyme disease is the most common tickborne disease. It is carried by Ixodes scapularis. This vector can also transmit the pathogens causing anaplasmosis, babesiosis, ehrlichiosis, and several more tickborne diseases in this region. There is also concern for other tick species, such as Amblyomma americanum, that are expanding their ranges northward. We launched a citizen science passive tick surveillance program in 2024 to investigate tick species ranges in the upper Midwest, as well as the pathogens carried by I. scapularis. We received over 12,000 ticks in the first two years of this program, primarily from Wisconsin. While we received submissions of adult A. americanum outside of their endemic range, we did not see evidence of establishment in our study area. We measured pathogen prevalence in adult female I. scapularis (n=707) and observed 51% positivity for Borrelia burgdorferi, 9% for Babesia microti, 9% for Anaplasma phagocytophilum, and 3% for Ehrlichia muris eauclairensis. Multiple pathogens were identified in 14% of tested specimens, and significant associations were observed between B. burgdorferi and B. microti, and B. burgdorferi and E. muris eauclairensis. Pathogen prevalences varied across time and geography. Our results can begin to inform risk assessment for tickborne diseases in our region. A non-technical version of this document with interactive maps is available here: https://storymaps.arcgis.com/stories/8008c9d710b5400599f3c6cf88b2c546 Our online data dashboard is available here: redcap.link/TICS