Hantavirus infections are rare in travellers and can cause severe disease. In this review of travel- and migration-associated infections reported to the GeoSentinel global surveillance network, 17 cases were identified from 2002 to 2025. New and Old World hantavirus infections were uncommon among returned travellers, but the 2026 cruise ship-associated Andes virus outbreak highlights the importance of early recognition in travellers.

Oceanic-atmospheric interactions significantly influence regional rainfall and vector-borne disease dynamics. Travel-related dengue cases serve as effective sentinels for dengue transmission, yet the impact of sea surface temperature (SST) variability on their occurrence remains under explored. Here we analyzed 2000–2019 GeoSentinel traveler dengue data alongside ERA5 SST and precipitation anomalies to assess correlations across global ocean basins. We identified that dominant SST variability modes in the Indian, Pacific, and Atlantic Oceans are remotely associated with dengue incidence in regions exhibiting strong seasonal precipitation patterns. These SST-driven rainfall variations likely modulate vector ecology and dengue transmission. Incorporating SST and precipitation anomalies into dengue forecasting models could enhance outbreak prediction and public health preparedness, providing a valuable adjunct to existing tools.

During September 2025–January 2026, 111 travellers (61 female/50 male; median age: 53 years) who acquired chikungunya virus (CHIKV) in Cuba were reported to GeoSentinel. Upon return, 64.2% (70/109) were potentially viraemic. Only 8.2% (9/98) had received pre-travel consultations. The CHIKV was of East-Central-South Africa genotype, closely related to Brazilian strains. International travellers can serve as arboviral outbreak sentinels and, if viraemic, risk introducing CHIKV into areas with established Aedes spp. vectors. Their effective surveillance can trigger adequate public health responses.

Novel respiratory pathogens have pandemic potential, making epidemiologic surveillance of acute lower respiratory tract infections (acute LRTI) a global public health priority. Monitoring acute LRTI among international travelers provides an underutilized opportunity to complement existing surveillance systems, though reliable denominator data on travel volume are often unavailable. We aimed to develop and validate a framework for detecting acute LRTI outbreaks among international travelers in the absence of reliable denominator data. Using syndromic and etiologic GeoSentinel data from 2015 to 2019, we modeled baseline LRTI epidemiology in travelers by comparing generalized linear mixed models (GLMMs) and selecting the preferred model using out-of-sample metrics. A robust Shewhart control-chart framework, accounting for increases in travel volume under non-epidemic conditions, was applied to detect deviations from expected trends and retrospectively to 2020 data from 64 countries to identify early COVID-19 signals. The preferred hybrid autoregressive GLMM, incorporating country-specific fixed effects, random seasonal effects, and a latent temporal autocorrelation structure, demonstrated adequate goodness-of-fit across pre-pandemic and post-pandemic (2023 to 2024) periods. The framework detected an early syndromic signal in China under the conservative assumption of up to a threefold increase in travel volume, consistent with COVID-19 emergence; a signal was also detected in Italy, driven primarily by influenza rather than novel syndromic cases. Combining traveler surveillance with this statistical framework may support early detection of acute LRTI outbreaks despite absent denominator data, positioning GeoSentinel as a valuable complementary network for global health security. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The International Society of Travel Medicine (ISTM) and the Centers for Disease Control and Prevention (CDC) support GeoSentinel, the Global Surveillance Network of ISTM, through a Cooperative Agreement (1 U01 CK000632-05). Additional support was provided by the Public Health Agency of Canada, the GeoSentinel Foundation, and the Italian Ministry of Health through Ricerca Corrente (Linea 1) funds awarded to IRCCS Sacro Cuore Don Calabria. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study used routine public health surveillance data from the GeoSentinel Surveillance Network, involving no intervention beyond standard clinical care. This activity was reviewed by the Centers for Disease Control and Prevention (CDC), deemed not research, and conducted consistent with applicable federal law and CDC policy. Institutional review board approval was therefore not required. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Aggregate epidemiological and clinical data supporting the findings of this study are included in the article. De-identified individual-level data are not publicly available because they were collected through routine public health surveillance and are subject to data protection and institutional restrictions. R functions used for statistical modeling can be found at https://github.com/SHeidema/ilitools. GeoSentinel, 1 U01 CK000632-05

BackgroundViral Respiratory Tract Infections (VRTIs) are a major public health threat. Early detection and preventive measures are key to controlling their spread. Current machine learning approaches often depend on symptom onset, costly equipment, trained personnel, and slow results. This study aims to evaluate whether a machine learning algorithm using physiological data from wearable biosensors during a constant-rate stair-stepping task (3-min test, 2-min recovery) can predict inflammation levels, and to identify the most predictive indicators of VRTI.Methods55 Healthy participants (27 males and 28 females) aged 18–59 years, were recruited and inoculated with a live influenza vaccine to induce an immune response, assessed via changes in circulating inflammatory biomarkers. Physiological markers, including breathing rate and heart rate, during a series of clinically controlled stair tests, were monitored by a wearable biosensor. These data were collected to develop a prediction model using gradient-boosting machine learning algorithms combined with hyperparameter tuning and a leave-one-subject-out method to train the models.ResultsThe study developed a predictive model that accurately estimates inflammation levels in individuals. Features from heart rate variability (HRV) showed the greatest potential, with 70% sensitivity and 77% specificity, and physiological markers from controlled stair tests correlated with VRTI-related inflammatory responses.ImpactThe prediction model linked to stair-stepping tests offers clinicians and the public a tool for self-monitoring and early intervention. Using machine learning and physiological markers, especially HRV features, it can help guide timely treatments and reduce the impact of future outbreaks.

BACKGROUND:Recent global epidemics and pandemics have highlighted the need for adequate diagnostic capacities to respond to emerging threats. Strengthening operational capacities can lead to improved preparation; investing in emergency response infrastructure may diminish progression of outbreaks and prevent escalation. METHODS:An email-linked survey was sent January-March-2025 to two global infectious disease surveillance networks' (GeoSentinel and TropNet) participating clinics assessing capacity for Oropouche virus (OROV) diagnostic testing. Data on testing capacity for other arboviruses was also requested. RESULTS:Responses were obtained for 58 GeoSentinel/TropNet sites (58/104, 55.8%): 50% responding sites (29/58) had OROV diagnostic testing available at a public reference laboratory; 23 sites (40%) had capacity for OROV RNA detection; 10 sites (17%) had OROV serological testing onsite. Estimated median turn-around times from phlebotomy-molecular OROV results were 4 days onsite and 6 days at the reference laboratory. Viral culture was available onsite at 9% of sites (at the reference laboratory for 26%). Molecular diagnostics availability for other arboviruses onsite showed >50% could test for at least one other arbovirus: dengue virus (31/58, 53%), chikungunya virus (29/58, 50%), West Nile virus (22/58, 38%) and yellow fever virus (12/58, 21%). Onsite serologic testing for non-OROV arboviruses was available at 39/58 sites (67%). CONCLUSIONS:The survey identified potential weaknesses in novel pathogen preparedness with respect to diagnostic capacity for OROV testing at specialized travel medicine clinics participating in two international networks. These findings provide an opportunity to implement measures to improve communication and planning and to strengthen diagnostic infrastructure prior to future outbreaks.

In the wake of a large outbreak in Reunion and Mayotte the GeoSentinel network has been signalling chikungunya cases among returning travellers acquired in multiple African and Asian countries between August 1st 2024 and June 10th 2025. These surveillance data suggest a resurgence of chikungunya in the Indian Ocean Region.

BACKGROUND:The global resurgence of measles is a threat to measles elimination campaigns. Measles importations by international travelers have been identified as a risk factor for outbreaks. METHODS:We reviewed measles cases among international travelers and migrants reported to the GeoSentinel network. RESULTS:From May 2019 through June 2025, GeoSentinel recorded 53 measles cases among travelers imported into 15 different countries. Travelers of all age groups were affected, and 74 % were 21 years or older. Thirty-three travelers (61 %) were hospitalized. Seventy-nine percent of cases reported no or unknown history of vaccination against measles. CONCLUSIONS:Against a background of increasing numbers of measles cases and outbreaks globally, GeoSentinel observed a stable trend of measles importations by international travelers. Measles caused considerable morbidity among travelers. Immunization effectively prevents measles in more than 97 % of individuals. Pretravel consultations provide an important opportunity to promote vaccination coverage for all vaccine-preventable diseases, including measles.

BACKGROUND:Presymptomatic or asymptomatic immune system signals and subclinical physiological changes might provide a more objective measure of early viral upper respiratory tract infections (VRTIs) compared with symptom-based detection. We aimed to use multimodal wearable sensors, host-response biomarkers, and machine learning to predict systemic inflammation following controlled exposure to a live attenuated influenza vaccine, without relying on symptoms. METHODS:WE SENSE study is a single-centre (McGill University Health Center, Montreal, QC, Canada), prospective controlled trial that recruited healthy adults aged 18-59 years who had not received or were not planning to receive the seasonal influenza vaccine or any other vaccine during the study period. We excluded participants with any infectious symptoms within 7 days before screening. We collected physiological and activity data (eg, heart rate, breathing rate, and acceleration) through continuous monitoring with a smart ring (Oura ring Gen 2, Oura Oy, Finland), smart watch (Biobeat watch, Biobeat Technologies, Israel), and smart shirt (Astroskin-Hexoskin shirt, Hexoskin, Canada) along with high temporal resolution systemic inflammatory biomarker mapping over 12 days (7 days before inoculation and 5 days after). We frequently tested participants both before and after inoculation via PCR for respiratory pathogens, and monitored them via apps for symptoms and free-text annotations. Machine learning algorithms predicting systemic inflammatory surges were trained (35 participants), validated (ten participants), and tested (ten participants) using gradient-boosting techniques. FINDINGS:Between Dec 10, 2021, and Feb, 28, 2022, we enrolled 56 participants, of whom 55 had available data; all 55 participants continuously wore the Oura ring, 54 participants wore the Astroskin-Hexoskin shirt, and 50 wore the Biobeat watch. 27 (49%) participants were female and 28 (51%) were male; 31 (56%) participants were White, eight (15%) were Asian, four (7%) were Black, two (4%) were Latino or Hispanic, and ten (18%) did not disclose. We used model 2, which included handpicked features from the Oura ring night-time data, as the candidate model because it was built on the lowest number of features (more practical). This model predicted inflammatory surges with receiver operating characteristic area under the curve (ROC-AUC) of 0·73 (95% CI 0·71-0·74) for real-time prediction and 0·89 (0·87-0·90) for a 24-h tolerance prediction window (24h-tol) using night-time data from the Oura ring. Incorporating both night-time and daytime data from the Astroskin-Hexoskin shirt yielded ROC-AUC values of 0·73 (0·71-0·75) for real-time and 0·91 (0·90-0·92) for 24h-tol along with improved precision (ie, specificity [0·83, 0·79-0·87] and F1 score [0·65, 0·58-0·71]). The model based on symptoms alone had lower performance, with ROC-AUC values of 0·66 (0·63-0·68) for real-time and 0·79 (0·77-0·82) for 24h-tol. INTERPRETATION:Systemic inflammatory biomarkers coupled with physiological data from wearable biosensors provided rich and objective data from which to train machine learning algorithms to predict systemic inflammation from a low-grade influenza challenge. This approach outperformed symptom-based detection and has the potential to improve detection of VRTIs such as influenza and decrease time to detection, even among asymptomatic people. FUNDING:The Canadian Institutes of Health Research.

Highlight Severe malaria definitions guide treatment and triage but may not reflect traveller risks in non-endemic settings. Two recent studies found isolated hyperparasitemia in travellers rarely predicts critical disease, questioning the widely recommended need for intravenous (IV) therapy in such cases. Revisiting severity criteria could improve overall management and triage of malaria in travellers.

Treatment with rituximab for systemic autoimmune rheumatic diseases (SARD) increases morbidity and mortality following COVID-19 infection,[1] and reduces antibody responses to vaccination. We evaluated humoral responses following fourth or fifth doses of either a protein subunit (PSV) or messenger RNA (mRNA) vaccines. We recruited adults with SARDs on rituximab post-third or fourth mRNA COVID-19 vaccine in an open-label, non-randomized, comparative trial. Participants chose to receive either a fourth dose of mRNA (Spikevax®) or PSV (NuvaxovidTM) vaccines. Patients who already received a fourth dose of mRNA vaccine were offered PSV as their fifth dose. Humoral vaccine-responses were determined pre, 28 days and 6 months post-vaccination. Plasma and sera were evaluated for anti-receptor binding domain (anti-RBD) by ELISA, and for neutralizing antibodies to Wuhan pseudotyped lentiviruses. We used descriptive statistics for demographics and ANOVA for immunogenicity. We studied 86 participants with rheumatoid arthritis (39%), ANCA vasculitis (32%), idiopathic inflammatory myositis (9%), systemic lupus erythematosus (8%), systemic sclerosis (7%), and undifferentiated SARDs (4%). Mean (SD) age was 57.3 (15.3); 73% were female; 91% White; 23% were on prednisone, 21% on antimalarials, and 42% on other immunosuppressors. Of those receiving a fourth dose (N=49) more chose Spikevax® (n=35) than NuvaxovidTM (N=14); 37 participants chose NuvaxovidTM for their fifth dose. An increase of anti-RBD response at 28 days post-vaccination was present in those receiving a fourth-dose mRNA vaccine, but not in those receiving fourth-dose PSV (Figure 1). In those receiving fifth-dose PSV, anti-RBD titers decreased at 6 months when compared to those at 28 days, while anti-RBD remained high in fourth-dose mRNA recipients. The fourth-dose mRNA recipients had higher neutralization titers against the Wuhan strain at 28 days compared to their pre-vaccination titers; this was not observed after the fourth dose of PSV. For all groups, the neutralizing response significantly decreased at 6 months post-vaccination compared to day 28. Figure 1 Anti-RBD antibody levels pre-vaccination (day 1) and at 28 days and 180 days post-vaccination . The line and the diamond inside the box indicate the median and the mean, respectively. Outliners are displayed bycirclered (○). In SARDs patients on rituximab, both fourth and fifth dose PSV vaccine recipients had decreased anti-RBD titers at 6 months, while post fourth-dose mRNA recipients increased their anti-RBD up to 6 months post-vaccination. Overall, humoral response in mRNA vaccine recipients seemed superior to those receiving PSV. This emphasizes the importance of thorough evaluation of new COVID-19 vaccines in the immunocompromised. [1.] Strangfeld A. Ann Rheum Dis 2021;80:930-42.

People living with systemic autoimmune rheumatic diseases (SARD) on B-cell depletion agents have impaired immunogenicity and increased vulnerability to severe COVID-19. We assessed the 7-day solicited reactogenicity and safety of booster doses following COVID-19 vaccine primary series. We recruited adults with SARDs on rituximab post-third or fourth dose of a messenger RNA (mRNA) COVID-19 vaccine in an open-label, non-randomized, comparative trial. Participants chose to receive either a fourth dose of mRNA Spikevax® or NuvaxovidTM, a protein subunit vaccine (PSV). Patients who had already received a fourth dose of mRNA vaccine were offered the PSV as their fifth dose. From study entry, up to 180 days post-booster, subjects self-reported solicited 7-days reactogenicity, and unsolicited adverse events, adverse events of special interest (AESI) (defined as medically confirmed flares of the underlying SARD), new COVID-19 infections, and serious adverse events (SAEs) (requiring hospitalization). We used descriptive statistics for demographics and chi-square tests to report reactogenicity and adverse events. We recruited 86 participants with rheumatoid arthritis (39%), ANCA vasculitis (32%), idiopathic inflammatory myositis (9%), systemic lupus erythematosus (8%), systemic sclerosis (7%), and undifferentiated SARDs (4%). Mean (SD) age was 57.3 (15.3); 73% were female; 91% White; 23% were on prednisone, 21% on antimalarials, and 42% on other immunosuppressors. The most significant reactogenicity manifestations were fever, erythema, swelling and pain. The proportion of side effects for all types of AEs were similar comparing the fourth-dose mRNA versus the fourth-dose PSV, and the fourth-dose PSV versus the fifth-dose PSV. Fever was only present in the fourth-dose mRNA group; erythema and swelling were reported more often in fifth-dose PSV vs fourth-dose mRNA; and pain significantly more in fourth-dose mRNA versus 5th-dose PSV. Disease flares (N=3, occurring at 14, 92, and 131 days) are presented in Table 1, along with COVID-19 and other infections (N=6). Including infections, there were 9 SAEs experienced by 8 participants (Table 1). There were no deaths. Table 1. Adverse Events of Special Interest and Serious Adverse Events. Three of 86 patients experienced a disease flare, and 9 others required hospitalization, mostly for COVID-19/other infections. A fourth or fifth booster dose of either an mRNA or a PSV vaccine was not clearly associated with unexpected vaccine reactions in rituximab-treated SARD patients. Revaccination of patients on rituximab with either mRNA or PSV vaccines appears safe.

Background:Cutaneous larva migrans (CLM) is one of the most common dermatoses affecting travellers to the tropics. Objective:To describe demographic and travel correlates of travellers returning to Canada from the Caribbean with CLM over a 10-year pre-pandemic period. Methods:Demographic and travel-related data on ill travellers encountered either during or after completion of their travel/migration and seen in any of eight CanTravNet sites from January 1, 2009, to December 31, 2018, with a final diagnosis of CLM were extracted and analyzed. During this time, access to first-line therapy, ivermectin, was available via Health Canada's Special Access Programme. Results:Of 17,644 travellers presenting to CanTravNet over the enrolment period, 328 (1.9%) returned from the Caribbean with CLM. The median age of travellers with CLM was 34 years (interquartile range: 25-50 years), with females accounting for 58% of cases. Ninety-five percent (n=313) travelled for tourism. Jamaica was the most common source country, with 216 cases (67%), followed by Barbados (n=27, 8%) and the Dominican Republic (n=23, 7%). Cases in 2018 were imported predominantly from Jamaica (n=58, 73%) and the Dominican Republic (n=12, 15%). Age, sex and purpose of travel were similar across years. The percentage of all imported cases of CLM that originated from the Caribbean increased from 9% in 2016 to 24.5% in 2018. Conclusion:Proportions and absolute numbers of CLM in travellers returning to Canada from the Caribbean are increasing. Improved awareness of this common dermatosis among physicians and travellers, as well as improved access to effective therapies, will reduce associated morbidity.

Oceanic-atmospheric interactions play a crucial role in the modulation of monsoon rainfall. This is the first study that directly investigates the impact of tropical sea surface temperature (SST) variability on the frequency of sentinel reporting of travel-related dengue from the Geosentinel global emerging infectious disease surveillance network, by using the latest climate reanalysis ERA-5 produced by the European Center for Medium-Range Weather Forecasts, for the period 2007 to 2019. More specifically, we explore lag structures and the associated spatial correlation patterns between travel-related dengue cases, SSTs, and total precipitation over the tropics. We found that the Indo-Pacific and Atlantic Ocean SSTs have a remote influence on dengue risk in global regions that exhibit distinct monsoon characteristics. The coupling between SST variations and rainfall is an important driver of travel-related dengue cases and could act as an early warning signal for outbreak preparedness and travel medicine preventive advice. Finally, our findings highlight the need to better understand the large-scale and local circulation response to changes in the pattern of tropical ocean warming, to be able to better predict extreme events such as droughts and floods and devise adaptation measures against dengue outbreaks.

The growing complexity of GeoSentinel surveillance data creates opportunities for novel data science-based outbreak detection methods. Challenges may be overcome by effective multidisciplinary collaboration. The early signals generated by outbreak detection methods using GeoSentinel data may influence policymaking, shape public health responses, and contribute to global disease control strategies.

Background Dengue is a leading cause of febrile illness among international travellers. We aimed to describe the epidemiology and clinical characteristics of imported dengue in returning travellers evaluated at GeoSentinel sites from 2007 to 2022. Methods We retrieved GeoSentinel records of dengue among travellers residing in non-endemic countries. We considered dengue confirmed when diagnosed by a positive dengue virus (DENV)-specific reverse-transcriptase polymerase chain reaction, positive NS-1 antigen and/or anti-DENV IgG seroconversion, and probable when diagnosed by single anti-DENV IgM or high-titre anti-DENV IgG detection. Severe dengue was defined as evidence of clinically significant plasma leakage or bleeding, organ failure, or shock, according to the 2009 World Health Organization guidance. Complicated dengue was defined as either severe dengue or dengue with presence of any warning sign. Analyses were descriptive. Results This analysis included 5958 travellers with confirmed (n = 4859; 81.6%) or probable (n = 1099; 18.4%) dengue. The median age was 33 years (range: <1-91); 3007 (50.5%) travellers were female. The median travel duration was 21 days (interquartile range [IQR]: 15-32). The median time between illness onset and GeoSentinel site visit was 7 days (IQR: 4-15). The most frequent reasons for travel were tourism (67.3%), visiting friends or relatives (12.2%) and business (11.0%). The most frequent regions of acquisition were South East Asia (50.4%), South Central Asia (14.9%), the Caribbean (10.9%) and South America (9.2%). Ninety-five (1.6%) travellers had complicated dengue, of whom 27 (0.5%) had severe dengue and one died. Of 2710 travellers with data available, 724 (26.7%) were hospitalized. The largest number of cases (n = 835) was reported in 2019. Conclusions A broad range of international travellers should be aware of the risk of acquiring dengue and receive appropriate pre-travel counselling regarding preventive measures. Prospective cohort studies are needed to further elucidate dengue risk by destination and over time, as well as severe outcomes and prolonged morbidity (long dengue) due to travel-related dengue.

We used cross-sectional data from 226 patients with monkeypox virus to investigate the association between anatomic exposure site and lesion development. Penile, anorectal, and oral exposures predicted lesion presence at correlating anatomic sites. Exposure site also predicted the first lesion site of the penis and anus.

Background Antimicrobial resistance (AMR) is a global health crisis, with Enterobacterales, including Escherichia coli and Klebsiella pneumoniae, playing significant roles. While international travel to low- and middle-income countries is linked to colonization with AMR Enterobacterales, the clinical implications, particularly the risk of subsequent infection, remain unclear due to limited data. We aimed to characterize E. coli and K. pneumoniae infections in travellers and the antimicrobial susceptibility profiles of their isolates.Methods We analysed data on E. coli and K. pneumoniae infections in travellers collected at GeoSentinel sites between 2015 and 2022, focusing on epidemiological, clinical and microbiological characteristics. We defined multi-drug resistance (MDR) as non-susceptibility to agents from at least three drug classes.Results Over the 8-year period, we included 655 patients (median age 41 years; 74% female) from 57 sites in 27 countries, with 584 E. coli and 72 K. pneumoniae infections. Common travel regions included sub-Saharan Africa, Southeast Asia and South-Central Asia. Urinary tract infections predominated. Almost half (45%) were hospitalized. Among infections with antimicrobial susceptibility data across three or more drug classes, 203/544 (37%) E. coli and 19/67 (28%) K. pneumoniae demonstrated MDR. Over one-third of E. coli and K. pneumoniae isolates were non-susceptible to third-generation cephalosporins and cotrimoxazole, with 38% and 28% non-susceptible to fluoroquinolones, respectively. Travellers to South-Central Asia most frequently had isolates non-susceptible to third-generation cephalosporins, fluoroquinolones and carbapenems. We observed increasing frequencies of phenotypic extended spectrum beta-lactamase and carbapenem resistance over time.Conclusions E. coli and K. pneumoniae infections in travellers, particularly those to Asia, may be challenging to empirically treat. Our analysis highlights the significant health risks these infections pose to travellers and emphasizes the escalating global threat of AMR. Enhanced, systematic AMR surveillance in travellers is needed, along with prospective data on infection risk post travel-related AMR organism acquisition.