Matthew Harmon Collins

Background: Dengue is a leading cause of febrile illness in endemic countries. Although adverse maternal and fetal outcomes have been reported during dengue infection, population-level evidence quantifying the association between pregnancy and severe dengue remains limited. We aimed to assess whether pregnancy was associated with increased risk of severe dengue among women of reproductive age with reported dengue in Colombia. Methods: We conducted a nationwide retrospective surveillance analysis of dengue cases reported in Colombia from 2013 to 2023. The primary analytic population was women aged 15–49 years with reported dengue and non-missing pregnancy status. The primary outcome was severe dengue disease, defined as severe dengue or dengue death. We estimated risk ratios (RRs) for the association between pregnancy and the severe dengue disease using Poisson regression with a log link and robust standard errors, adjusting for age, calendar year, and department. We estimated standardised predicted risks and conducted sensitivity analyses restricted to confirmed cases, laboratory-confirmed cases, severe dengue excluding deaths, and hospitalised cases. Findings: Among 924,616 reported dengue cases, 191,986 occurred among women of reproductive age, including 5572 (2·9%) during pregnancy. Severe dengue disease occurred in 174 (3·1%) pregnant women and 2469 (1·3%) non-pregnant women. Pregnancy was associated with increased risk of the severe dengue disease in crude analysis (RR 2·36, 95% CI 2·03–2·74) and after adjustment for age, calendar year, and department (adjusted RR 2·64, 95% CI 2·26–3·07). Standardised predicted risks were 3·48% for pregnant women and 1·32% for non-pregnant women, corresponding to 21·6 additional severe dengue disease events per 1000 reported dengue cases during pregnancy. The association was consistent across sensitivity analyses. Among pregnant women, rural or dispersed residence was associated with higher severe dengue risk than urban residence (adjusted RR 1·47, 95% CI 1·06–2·03). Interpretation: Pregnancy was associated with substantially higher risk of severe dengue or dengue death among women of reproductive age with reported dengue in Colombia. Pregnant women, particularly those living in rural or dispersed areas, should be considered in the design and delivery of dengue prevention and prioritised for early clinical assessment, close follow-up, and referral during dengue outbreaks. Funding: Ministerio de Ciencia, Tecnología e Innovación, Colombia (Contract 592-2022).

Dengue and other Aedes-borne arboviruses remain major public health challenges in Brazil. Conventional vector control strategies have had limited long-term impact. Wolbachia introgression offers a promising complementary approach. As part of the EVITA Dengue trial, we assessed the success of wMel Wolbachia releases in achieving introgression and other entomological outcomes in Belo Horizonte.The EVITA Dengue trial (2020–2024) involved 58 school-based clusters randomized to continue standard vector control alone or combined with wMel Wolbachia releases. To protect the integrity of the ongoing blinded trial, we analyzed spatially-blinded mosquito release and monitoring data collected from March 2021 through December 2024. Entomological outcomes assessed were wMel introgression prevalence, contamination in control clusters, and the abundance of Wolbachia-uninfected (wMel-negative) Ae. aegypti.Intervention clusters achieved sustained wMel introgression with a median of 71% (IQR: 63–81%), and 90% of clusters exceeding the 60% per-protocol target during the per protocol period. Control clusters showed minimal contamination (median 0%, IQR: 0–9%). The intervention was associated with a 75% reduction in wMel-negative Ae. aegypti abundance (IRR 0.25; 95% CI: 0.22–0.29). Trajectory modeling identified three distinct patterns of trap-level introgression, with higher release intensity associated with more stable and sustained introgression.The wMel release strategy in Belo Horizonte successfully achieved sustained introgression and significantly reduced the wMel-negative Ae. aegypti population, supporting interpretation of the forthcoming EVITA Dengue clinical efficacy results.

: Dengue, chikungunya, and Zika are Aedes -borne diseases (ABDs) of global health significance. Epidemiological studies with sensitive case detection are critical for evaluating vector control strategies to prevent ABDs; however, data on which surveillance method is most effective are limited. The performance of five surveillance methods (home visits, phone calls, SMS reminders, toll-free phone line (TF) and the Ministry of Health surveillance platform) was assessed, and the clinical characteristics of ABD cases in the targeted indoor residual spraying trial, which quantified the efficacy of preventive indoor residual insecticide applications against ABDs in Merida, Mexico, were described. A cohort of 4,461 children was monitored over three transmission seasons (July-December 2021–2023), with surveillance methods rotated weekly to detect illnesses. Kaplan–Meier curves and log-rank tests compared the time from symptom onset to laboratory testing across methods. Analysis of variance, t- and χ ² tests assessed differences in utilization of surveillance methods across demographic factors. Of 1,902 illnesses detected, 920 (48.4%) met suspected ABD criteria; 825 provided blood samples (89%), and 422 (51%) were confirmed as ABDs. Dengue represented 70.4% of confirmed cases ( n = 297/422). Among confirmed cases, clinical manifestations were diverse, with fever (>94%), myalgia (80–100%), and headache (70–100%) being most frequent. Twenty-seven patients (9%; n = 27/297) had dengue with warning signs. TF detected 55.2% ( n = 233/422) of confirmed cases and achieved the fastest time to laboratory testing. These results demonstrate case detection can be optimized. TF proved effective in rapidly identifying symptomatic reports, underscoring the value of integrated, low-barrier reporting systems for early arboviral detection.

Yellow fever remains a major public health threat in endemic and re-emerging regions of Africa and South America, with recent outbreaks highlighting persistent gaps in prevention and surveillance. Pregnant women represent a particularly vulnerable population, yet the epidemiology, clinical impact, and preventive strategies for yellow fever in pregnancy are insufficiently characterized. Physiological and immunological changes during gestation may influence host responses to infection; however, current evidence does not demonstrate increased susceptibility to or severity of yellow fever during pregnancy. Adverse materno-fetal outcomes, including miscarriage, stillbirth, preterm birth, and, in rare cases, perinatal transmission, have been reported but remain poorly characterized. Diagnostic challenges, overlapping clinical presentations with other arboviral and hepatic diseases, and limited access to specialized care further complicate clinical management in many endemic settings. This perspective provides a comprehensive overview of yellow fever in pregnancy during the 2024–2026 outbreak in the Americas, including a risk-stratification framework for prevention. We summarize current evidence on epidemiology, pathophysiology, diagnosis, and supportive care, and examine prevention strategies with particular emphasis on vaccination. Accumulated observational evidence and substantial real-world experience have not demonstrated an increased risk of serious adverse events and generally support the effectiveness of yellow fever vaccination during pregnancy when administered with appropriate clinical judgment. In high-risk settings, the benefits of maternal immunization clearly outweigh theoretical concerns, supporting a flexible, risk-based approach, despite relatively limited evidence. We also discuss national and international policies, post-pregnancy booster recommendations, and the importance of integrating vaccination assessment into antenatal care. Finally, we highlight critical knowledge gaps and research priorities, including the need for prospective registries and strengthened pharmacovigilance. Coordinated clinical and public health strategies are essential to protect maternal and neonatal health and to reduce the burden of yellow fever in endemic and re-emerging settings.

Yellow fever remains a major public health threat in endemic and re-emerging regions of Africa and South America, with recent outbreaks highlighting persistent gaps in prevention and surveillance. Pregnant women represent a particularly vulnerable population, yet the epidemiology, clinical impact, and preventive strategies for yellow fever in pregnancy are insufficiently characterized. Physiological and immunological changes during gestation may increase susceptibility to severe disease and contribute to adverse maternal and fetal outcomes, including miscarriage, stillbirth, preterm birth, and, in rare cases, perinatal transmission. Diagnostic challenges, overlapping clinical presentations with other arboviral and hepatic diseases, and limited access to specialized care further complicate clinical management in many endemic settings. This perspective provides a comprehensive overview of yellow fever in pregnancy during the 2024–2026 outbreak in the Americas, including a risk-stratification framework for prevention. We summarize current evidence on epidemiology, pathophysiology, diagnosis, and supportive care, and examine prevention strategies with particular emphasis on vaccination. Accumulated observational evidence and substantial real-world experience have not demonstrated an increased risk of serious adverse events and generally support the effectiveness of yellow fever vaccination during pregnancy when administered with appropriate clinical judgment. In high-risk settings, the benefits of maternal immunization clearly outweigh theoretical concerns, supporting a flexible, risk-based approach, despite relatively limited evidence. We also discuss national and international policies, post-pregnancy booster recommendations, and the importance of integrating vaccination assessment into antenatal care. Finally, we highlight critical knowledge gaps and research priorities, including the need for prospective registries and strengthened pharmacovigilance. Coordinated clinical and public health strategies are essential to protect maternal and neonatal health and to reduce the burden of yellow fever in endemic and re-emerging settings.

Historically, DENV-4 has been rarely associated with epidemics and has been less well-studied than DENV-1 to -3. Epidemic dengue struck several South and Central American countries in 2022, with Nicaragua reporting the highest incidence. In an acute febrile illness (AFI) cohort enrolled from June to September 2022, 58 (34%) of 172 patients had PCR-confirmed dengue, of which 46 (79%) were serotyped as DENV-4. In this cohort, acute dengue, as a proportion of AFI, increased from 8% in June to a peak of 58% in August. Genome sequencing and phylogenetic analysis identified a lineage of DENV-4 Genotype IIb (GIIb) with six amino acid substitutions on the surface-exposed regions of the envelope (E) protein as compared to a reference sequence from 2005. Indeed, two of these mutations appear to be novel and located at G172E or near N174K, an antigenic epitope on domain I. Most (90%, 43/48) DENV-4 patients had pre-existing DENV IgG (secondary dengue), at the acute phase. Secondary dengue was associated with the male sex (prevalence ratio (PR)), 6.88) and being younger than 11 years of age (PR, 8.38). Further analysis showed no association between past Zika exposure and DENV-4 acute illness in older subjects (≥12 years of age). In conclusion, our study describes an epidemic of DENV-4 in León, Nicaragua, associated with a novel lineage of genotype GIIb, which contains two amino acid changes not observed in DENV-4 before 2022.

Current Mpox vaccination guidance focuses on sexual risk factors, which may miss some travelers at risk for illness, particularly adults and children visiting friends and relatives in areas experiencing clade 1 Mpox transmission. Travel clinics can play an important role in vaccination to prevent illness and limit spread.

Background: Invasive nontypeable Haemophilus influenzae (NTHi) infections increased dramatically in the Atlanta area in 2017–2018. Most isolates from these infections belonged to two closely related genetic lineages and were likely being spread through sexual networks of men living with HIV. Case Summary: We present a case of a 63-year-old male with well-controlled HIV and treated NTHi pericarditis and bacteremia who we diagnosed with an infected right superficial femoral artery pseudoaneurysm due to NTHi. The causative strain belonged to one of the lineages identified in the 2017–2018 case clusters. Conclusion: This case illustrates that novel disease phenotypes continue to emerge for unusually pathogenic strains of NTHi.

While a live-attenuated Yellow fever (YF) vaccine is known to elicit durable immunity, antibody titers may wane after vaccination. This study evaluated the long-term immunity after vaccination against YF among individuals who reside in Korea and received vaccination with YF virus-17D prior to international travel. Serum was collected between December 2018 and December 2019 at the National Medical Center, Republic of Korea from YF vaccine recipients who were vaccinated more than five years prior to sample collection. Long-term immunity against YF was assessed using three serological assays: IgG enzyme‐linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), and focus reduction neutralization test (FRNT). Sixty seven subjects were enrolled. The overall positivity rates for FRNT50, IFA and ELISA were 97.0%, 86.6% and 26.9%, respectively, in a time-variable, cross-sectional sample of the cohort. While 93.8% (15/16) of samples collected ≥10 years post-vaccination remained positive by FRNT50, a significant inverse correlation was observed between FRNT50 titer and interval after vaccination (r=-0.385, p=0.001). Humoral immunity against YF was well preserved among the Korean individuals who were more than five years post-vaccination. IFA testing yielded results similar to FRNT50 testing, which may justify further development of the IFA to screen for waning immunity among those with previous YF vaccination.