The Amapa State, Brazil, in the Amazon region and bordering French Guiana, is a strategic sentinel location for infectious disease surveillance. Ecological pressures such as deforestation, artisanal gold mining, and high human mobility contribute to complex transmission dynamics of arboviruses, bacterial infections, and other pathogens. This study aims to characterize the etiologies of acute febrile illness (AFI) reported in Amapa State in 2018-2020, focusing on arbovirus circulation, bacterial contributions, and emerging pathogens. A retrospective analysis was carried out with 727 AFI cases. Laboratory diagnoses were established using molecular and serological assays, with systematic testing for different pathogens. Definitive diagnoses were obtained in 185 individuals (25.4%), yielding 209 positive results and including 23 cases of co-infection. Dengue virus was the predominant etiological agent (n=109, 52%), followed by leptospirosis (n=20, 9.5%), chikungunya virus (n=16, 7.6%), parvovirus B19 (n=16, 7.6%), measles (n=15, 7.1%), zika virus (n=10, 4.8%), mayaro virus (n=1,0.5%), and other bacterial infections (n=5, 2.4%). Isolated cases of hepatitis A and B, malaria, SARS-CoV-2, enterovirus, and acute Chagas disease were also identified. No hepatitis E virus or oropouche cases were detected. Dengue virus was the leading cause of AFI. Leptospirosis, chikungunya virus, and parvovirus B19 were other prevalent and often underrecognized contributors. The detection of additional viruses highlights Amapa State as a potential zone of "silent expansion" for emerging arboviruses. Co-detection of multiple pathogens underscores diagnostic complexity in regions with overlapping transmission. Strengthening surveillance, expanding laboratory capacity, and prioritizing differential diagnostics are essential to capture epidemiological dynamics and guide public health interventions.

After the recertification of measles elimination in Brazil, outbreaks associated with imported cases may occur in pockets of susceptible individuals, including communities with low vaccination coverage. This study describes an outbreak investigation conducted in 2025 in Campos Lindos, Tocantins State, Brazil. In total, 25 cases were confirmed, mostly among unvaccinated Old Believers (a traditional community of Russian origin) following viral introduction linked to international travel, with transmission occurring predominantly within the community. Outbreak response measures, including ring vaccination and active case finding, interrupted transmission after 12 weeks with no new cases. The rapid response was effective and reinforces the importance of identifying susceptibility pockets in the population to prevent measles reintroduction.

In 2026, the National Foundation for Infectious Diseases (NFID), with the Infectious Diseases Society of America (IDSA), convened a Measles Summit in response to the largest U.S. measles resurgence in over three decades, with more than 3,000 confirmed cases mostly among unvaccinated individuals. Many clinicians and public health professionals have limited firsthand measles experience, underscoring the need for clinical guidance. In this commentary, we examine immune globulin (IG) use for measles post-exposure prophylaxis (PEP) amid fragile supply and logistical challenges. GamaSTAN®, the sole Food and Drug Administration (FDA)-licensed intramuscular IG product, faces episodic availability, non-returnable single-vial economics, and a 2013 recommendation to double the PEP dose, increasing per-patient demand. IVIG is increasingly employed when patients weigh 30 kg or more, beyond the weight at which an adequate dose of immune globulin can be given intramuscularly, or when IMIG supply is constrained, while concurrent lot withdrawals compromise institutional formularies. We review evidence-based patient selection for PEP, emphasizing that the Measles, Mumps, and Rubella (MMR) vaccine remains first-line within 72 hours of exposure, with IG reserved when vaccination is contraindicated or potentially ineffective. Immunosuppressive therapies vary widely in their effects on the safety and efficacy of live vaccines. We therefore argue against categorizing every biologic, immunomodulator, or steroid as an automatic MMR contraindication, which would overestimate IG-PEP demand and preclude MMR for eligible patients. We propose class-specific stratification and an electronic health record decision-support rule to better align IG demand with genuine need. Finally, we address declining potency standards for measles antibody, attributable to waning donor titers, and offer guidance on dosing, multi-site pediatric administration, and infusion logistics within the PEP window.

Childhood vaccination remains one of the most effective public health interventions, yet coverage is often lowest in settings affected by conflict and structural disadvantage. Cameroon has faced overlapping humanitarian crises in its Far North, North-West, and South-West regions, but evidence comparing determinants of full vaccination between conflict-affected and non-conflict regions remains limited. This study explores determinants of full vaccination status in 12-23 months children in Cameroon, stratified by conflict regions.

SUMMARYMeasles virus (MeV) is considered the most contagious human virus. This review critically examines explanations for MeV's extraordinary transmissibility. Although substantial progress has been made in understanding MeV infection, pathogenesis, and host spread, the fundamental question of why MeV is markedly more transmissible than other structurally similar respiratory viruses within the same taxonomic families remains unresolved. Many commonly cited explanations are either incorrect, oversimplified, or insufficiently supported by rigorous experimental evidence. Notably, there is a striking lack of studies that directly investigate the mechanisms governing MeV transmission. This knowledge gap persists in part because humans are the only natural reservoir for MeV, and thus the most relevant experimental models can be costly, technically challenging, and limited in ability. Moreover, studies addressing MeV environmental stability have relied largely on in vitro laboratory conditions that may have limited relevance to real-world transmission scenarios. While these studies have yielded useful observations, they often lack definitive mechanistic insight into efficient host-to-host spread. In this review, we discuss multiple strategies to investigate and define the efficient transmission of MeV, including (i) epidemiology, (ii) stability in controlled environments, (iii) infectious dose, (iv) incubation period, and (v) shedding from the respiratory epithelium. As will be discussed, quantitative, head-to-head comparisons of MeV transmission dynamics with those of other common respiratory viruses, such as influenza virus, rhinovirus, and respiratory syncytial virus, are notably absent. A clearer understanding of the mechanisms that govern efficient MeV transmission may inform strategies to reduce spread in educational, healthcare, and community settings.

Multiple sclerosis (MS) is a complex, multifactorial neurodegenerative disease with an aetiology that is still partially elusive. Several risk factors are associated with MS development including genetic predisposition and various environmental stressors; however, recently, viral infections have gained significant attention as a crucial environmental trigger. Despite the well-established link between Epstein-Barr virus (EBV) and MS susceptibility, a single-pathogen model fails to clearly characterise the molecular cascades driving the disease, suggesting that the transition from infection to autoimmune response involves more than one viral agent. In this review we examine the speculation that the interactions among different neurotropic viruses could serve a collective causative role in MS, which is under-researched in the literature at present. We summarise contradictory evidence on the role of different viral agents, including the Herpesviridae family (Human Cytomegalovirus, EBV, Herpes Simplex Viruses HSV-1 and HSV-2, and Varicella Zoster Virus), Paramyxoviridae family (Measles Virus and Rubella Virus), Influenza virus, SARS-CoV-2, and Human Endogenous Retroviruses (HERVs). Through interplay within shared molecular pathways, immune modulation, and activation of latent infections, these viruses may collectively influence the inflammatory and demyelinating processes that characterise MS. This review evaluates the etiological role of viral interplay in MS through the cumulative and interactive effects of these pathogens. The available epidemiological, immunological, and experimental data converge on the concept that viral co-exposures act synergistically to shape MS susceptibility in genetically predisposed individuals. Characterising these viral interactions presents a new research direction for the identification of novel biomarkers and the development of preventative strategies through the targeted control of viral networks.

Undernutrition and infectious diseases pose a double threat to child survival, especially in areas with a high malnutrition burden and low vaccination coverage. In this study, we evaluated whether distributing preventive small-quantity lipid-based nutrient supplements (SQ-LNS) alongside routine immunization services may increase vaccine uptake in a pediatric, pragmatic, cluster-randomized controlled trial in northern Nigeria. Twenty geographically defined clusters across two Local Government Areas were randomized 1:1 to the NutriVax strategy (intervention) or standard National Program of Immunization (NPI) services (control). NutriVax provided a monthly ration of SQ-LNS to children aged 6-23 months after routine NPI delivery at primary healthcare centers. The primary outcome was coverage of the first dose of measles-containing vaccine (MCV1) verified by vaccination card among children aged 12-23 months, assessed in an endline population-based household cross-sectional survey 12 months after conducting a similar baseline survey. The endline survey included 1,604 children (801 control, 803 NutriVax); 48% of children surveyed in intervention clusters had ever received SQ-LNS. The odds of receiving card-verified MCV1 were two times higher in the NutriVax arm than in the control arm (odds ratio = 2.08, 95% confidence interval (CI): 1.30-3.35, P = 0.004). The difference-in-differences, cluster conditional analysis indicated a 20.1 percentage-point (pp) increase in MCV1 coverage from baseline (95% CI: 13.7-26.5 pp, P < 0.0001) relative to the control arm. Co-delivering SQ-LNS with routine immunization substantially improved card-verified MCV1 uptake, supporting a scalable strategy to make progress toward targets set by the World Health Organization's Immunization Agenda 2030 in similar settings. ClinicalTrials.gov identifier: NCT06387511 .

The global resurgence of measles is a major public health concern. After the success of its Expanded Programme on Immunization, Bangladesh experienced a measles resurgence in 2026. The country faced major setbacks after measles vaccination coverage declined because of political instability, discontent among field-level staff, change in procurement policy, COVID-19-related service disruptions, and delayed supplementary immunization campaigns. During March 15-September 13, 2026, Bangladesh reported 170,638 suspected and 20,006 confirmed measles cases, including 919 deaths among suspected and 100 deaths among laboratory-confirmed cases. The outbreak disproportionately affected unvaccinated and underimmunized children. Political turmoil during 2024-2025 disrupted vaccine procurement, delayed mass vaccination campaigns, weakened the health workforce, and compromised financial and logistic continuity. Simultaneously, disruptions in vitamin A supplementation and worsening child malnutrition amplified disease severity. To prevent future resurgence, immunization programs must be depoliticized, supported by buffer vaccine stocks, strengthened through microlevel surveillance, and integrated with nutrition and primary healthcare services.

Nationwide surveillance in Bangladesh during April 2-May 27, 2026, identified a total of 67,079 suspected and 8,834 confirmed measles cases across 8 administrative divisions. Among suspected cases, 472 deaths were reported, and 88 deaths were reported among confirmed cases. Despite high reported vaccine coverage, transmission persisted amid residual immunity gaps. Vaccine stockouts, discontinued vaccination campaigns, and coverage overestimation likely contributed to Bangladesh's largest recorded measles outbreak.