Bifunctional Binder with Nucleophilic Lithium Polysulfide Immobilization Ability for High-Loading, High-Thickness Cathodes in Lithium-Sulfur Batteries.

Lithium-sulfur batteries remain a promising next-generation renewable energy storage device due to their high theoretical energy density over the current commercial lithium-ion battery technology. However, to have any practical viability toward reaching the theoretical value, high-loading cathodes with sufficient sulfur content and specifically the effect of nonconductive binders must be investigated. We consider the limitations of conventional binders for high-loading, high-thickness cathodes by integrating a bifunctional binder with a linear polyethylene chain and maleate-capped ends. The linear polymer allows for flexibility within the high-loading cathode whereas the maleate ends improve the polysulfide trapping ability with carbon-sulfur binding. With the strong polysulfide immobilization ability due to the nucleophilic binding, the binder achieves high sulfur loadings of 12 mg cm-2 with a high sulfur content of 80 wt %. The work serves as a proof of concept for exploring the incorporation of polymeric materials into sulfur cathodes to realize practical viability.

Pyrrolic-Type Nitrogen-Doped Hierarchical Macro/Mesoporous Carbon as a Bifunctional Host for High-Performance Thick Cathodes for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are highly considered as a next-generation energy storage device due to their high theoretical energy density. For practical viability, reasonable active-material loading of >4.0 mg cm-2 must be employed, at a cost to the intrinsic instability of sulfur cathodes. The incursion of lithium polysulfides (LiPS) at higher sulfur loadings results in low active material utilization and poor cell cycling capability. The use of high-surface-area hierarchical macro/mesoporous inverse opal (IOP) carbons to investigate the effects of pore volume and surface area on the electrochemical stability of high-loading, high-thickness cathodes for Li-S batteries is presented here. The IOP carbons are additionally doped with pyrrolic-type nitrogen groups (N-IOP) to act as a polar polysulfide mediator and enhance the active-material reutilization. With a high sulfur loading of 6.0 mg cm-2 , the Li-S cells assembled with IOP and N-IOP carbons are able to attain a high specific capacity of, respectively, 1242 and 1162 mA h g-1 . The N-IOP enables the Li-S cells to demonstrate good electrochemical performance over 300 cycles.

Thin-Layered Molybdenum Disulfide Nanoparticles as an Effective Polysulfide Mediator in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are attractive as sulfur offers an order of magnitude higher charge-storage capacity than the currently used insertion-compound cathodes. However, their practical viability is hampered by low electrochemical stability and efficiency, which results from severe polysulfide (LiPS) shuttling during cycling. We present here thin-layered MoS2 nanoparticles (MoS2-NPs) synthesized through a one-pot method and coated onto a commercial polymeric separator (as MoS2-NP-coated separator) as an effective LiPS mediator, facilitated by the nanodimension, polar interactions, and the better edge-binding sites of the MoS2-NPs. The resulting MoS2-NPs have an interlayer spacing of 0.55 nm and are stacked with a few layers. At a sulfur loading of 4.0 mg cm-2, the Li-S cell with a MoS2-NP-coated separator attains a peak discharge capacity of 983 mA h g-1, improving the electrochemical utilization of sulfur. The cell is able to maintain a high capacity of 525 mA h g-1 after 150 cycles at a C/5 rate. The MoS2-NPs are able to effectively anchor the LiPS species to their large S2- anions, enhancing the redox accessibility of sulfur cathodes and enabling better capacity retention.

Travelers' Diarrhea and Other Gastrointestinal Symptoms Among Boston-Area International Travelers.

AbstractThis prospective cohort study describes travelers' diarrhea (TD) and non-TD gastrointestinal (GI) symptoms among international travelers from the Boston area, the association of TD with traveler characteristics and dietary practices, use of prescribed antidiarrheal medications, and the impact of TD and non-TD GI symptoms on planned activities during and after travel. We included adults who received a pre-travel consultation at three Boston-area travel clinics and who completed a three-part survey: pre-travel, during travel, and post-travel (2-4 weeks after return). TD was defined as self-reported diarrhea with or without nausea/vomiting, abdominal pain, or fever. Demographic and travel characteristics were evaluated by χ2 test for categorical and Wilcoxon rank-sum test for continuous variables. Analysis of dietary practices used logistic generalized estimating equation models or logistic regression models. Of 628 travelers, 208 (33%) experienced TD and 45 (7%) experienced non-TD GI symptoms. Of 208 with TD, 128 (64%), 71 (36%), and 123 (62%) were prescribed ciprofloxacin, azithromycin, and/or loperamide before travel, respectively. Thirty-nine (36%) of 108 took ciprofloxacin, 20 (38%) of 55 took azithromycin, and 28 (28%) of 99 took loperamide during travel. Of 172 with TD during travel, 24% stopped planned activities, and 2% were hospitalized. Of 31 with non-TD GI symptoms during travel, six (13%) stopped planned activities. International travelers continue to experience diarrhea and other GI symptoms, resulting in disruption of planned activities and healthcare visits for some. Although these illnesses resulted in interruption of travel plans, a relatively small proportion took prescribed antibiotics.

Quantitative Analysis of Electrochemical and Electrode Stability with Low Self-Discharge Lithium-Sulfur Batteries.

The viability of employing high-capacity sulfur cathodes in building high-energy-density lithium-sulfur batteries is limited by rapid self-discharge, short shelf life, and severe structural degradation during cell resting (static instability). Unfortunately, the static instability has largely been ignored in the literature. We present in this letter a long-term self-discharge study by quantitatively analyzing the control lithium-sulfur batteries with a conventional cathode configuration, which provides meaningful insights into the cathode failure mechanisms during resting. Utilizing the understanding obtained with the control cells, we design and present low self-discharge (LSD) lithium-sulfur batteries for investigating the long-term self-discharge effect and electrode stability.

Self-reported illness among Boston-area international travelers: A prospective study.

BACKGROUND: The Boston Area Travel Medicine Network surveyed travelers on travel-related health problems. METHODS: Travelers were recruited 2009-2011 during pre-travel consultation at three clinics. The investigation included pre-travel data, weekly during-travel diaries, and a post-travel questionnaire. We analyzed demographics, trip characteristics, health problems experienced, and assessed the relationship between influenza vaccination, influenza prevention advice, and respiratory symptoms. RESULTS: Of 987 enrolled travelers, 628 (64%) completed all surveys, of which 400 (64%) reported health problems during and/or after travel; median trip duration was 12 days. Diarrhea affected the most people during travel (172) while runny/stuffy nose affected the most people after travel (95). Of those with health problems during travel, 25% stopped or altered plans; 1% were hospitalized. After travel, 21% stopped planned activities, 23% sought physician or other health advice; one traveler was hospitalized. Travelers who received influenza vaccination and influenza prevention advice had lower rates of respiratory symptoms than those that received influenza prevention advice alone (18% vs 28%, P = 0.03). CONCLUSIONS: A large proportion of Boston-area travelers reported health problems despite pre-travel consultation, resulting in inconveniences. The combination of influenza prevention advice and influenza immunization was associated with fewer respiratory symptoms than those who received influenza prevention advice alone.

A Polysulfide-Trapping Interface for Electrochemically Stable Sulfur Cathode Development.

Lithium-sulfur (Li-S) cells have a strong edge to become an inexpensive, high-capacity rechargeable battery system. However, currently, several prohibitive challenges occur within the sulfur core, especially the polysulfide-diffusion problem. To address these scientific issues, we present here a boron-doped multiwalled carbon nanotube coated separator (B-CNT-coated separator). The B-CNT-coated separator creates a polysulfide trap between the pure sulfur cathode and the polymeric separator as a "polysulfide-trapping interface," stabilizing the active material and allowing the dissolved polysulfides to activate the bulk sulfur cores. Therefore, the dissolved polysulfides change from causing fast capacity fade to assisting with the activation of bulk sulfur clusters in pure sulfur cathodes. Moreover, the heteroatom-doped polysulfide-trapping interface is currently one of the missing pieces of carbon-coated separators, which might inspire further studies in its effect and battery chemistry. Li-S cells employing B-CNT-coated separators (i) exhibit improved cyclability at various cycling rates from 0.2C to 1.0C rate and (ii) attain a high capacity retention rate of 60% with a low capacity fade rate of 0.04% cycle(-1) after 500 cycles. We believe that our B-CNT-coated separator could light up a new research area for integrating heteroatom-doped carbon into the flexible, lightweight, carbon-coated separator.

Malaria Prevention Strategies: Adherence Among Boston Area Travelers Visiting Malaria-Endemic Countries.

We conducted a prospective cohort study to assess adherence to malaria chemoprophylaxis, reasons for nonadherence, and use of other personal protective measures against malaria. We included adults traveling to malaria-endemic countries who were prescribed malaria chemoprophylaxis during a pre-travel consultation at three travel clinics in the Boston area and who completed three or more surveys: pre-travel, at least one weekly during travel, and post-travel (2-4 weeks after return). Of 370 participants, 335 (91%) took malaria chemoprophylaxis at least once and reported any missed doses; 265 (79%) reported completing all doses during travel. Adherence was not affected by weekly versus daily chemoprophylaxis, travel purpose, or duration of travel. Reasons for nonadherence included forgetfulness, side effects, and not seeing mosquitoes. Main reasons for declining to take prescribed chemoprophylaxis were peer advice, low perceived risk, and not seeing mosquitoes. Of 368 travelers, 79% used insect repellent, 46% used a bed net, and 61% slept in air conditioning at least once. Because travelers may be persuaded to stop taking medication by peer pressure, not seeing mosquitoes, and adverse reactions to medications, clinicians should be prepared to address these barriers and to empower travelers with strategies to manage common side effects of antimalarial medications.

Pre-Travel Medical Preparation of Business and Occupational Travelers: An Analysis of the Global TravEpiNet Consortium, 2009 to 2012.

OBJECTIVES: The aim of the study was to understand more about pre-travel preparations and itineraries of business and occupational travelers. METHODS: De-identified data from 18 Global TravEpiNet clinics from January 2009 to December 2012 were analyzed. RESULTS: Of 23,534 travelers, 61% were non-occupational and 39% occupational. Business travelers were more likely to be men, had short times to departure and shorter trip durations, and commonly refused influenza, meningococcal, and hepatitis B vaccines. Most business travelers indicated that employers suggested the pre-travel health consultation, whereas non-occupational travelers sought consultations because of travel health concerns. CONCLUSIONS: Sub-groups of occupational travelers have characteristic profiles, with business travelers being particularly distinct. Employers play a role in encouraging business travelers to seek pre-travel consultations. Such consultations, even if scheduled immediately before travel, can identify vaccination gaps and increase coverage.

Immunocompromised Travelers: Demographic Characteristics, Travel Destinations, and Pretravel Health Care from the U.S. Global TravEpiNet Consortium.

An increasing number of immunocompromised individuals are pursuing international travel, and a better understanding of their international travel patterns and pretravel health care is needed. We evaluated the clinical features, itineraries, and pretravel health care of 486 immunocompromised international travelers seen at Global TravEpiNet sites from January 2009 to June 2012. We used bivariate analyses and logistic regressions using random intercept models to compare demographic and travel characteristics, vaccines administered, and medications prescribed for immunocompromised travelers versus 30,702 immunocompetent travelers. Immunocompromised travelers pursued itineraries that were largely similar to those of immunocompetent travelers, with nearly one-third of such travelers visiting countries with low human development indices. Biological agents, including tumor necrosis factor blockers, were commonly used immunosuppressive medications among immunocompromised travelers. A strong collaboration between travel-medicine specialists, primary care doctors, and specialist physicians is needed to prepare immunocompromised people for international travel. Incorporating routine questioning and planning regarding travel into the primary care visits of immunocompromised people may be useful.

Travel-associated disease among US residents visiting US GeoSentinel clinics after return from international travel.

BACKGROUND: US residents make 60 million international trips annually. Family practice providers need to be aware of travel-associated diseases affecting this growing mobile population. OBJECTIVE: To describe demographics, travel characteristics and clinical diagnoses of US residents who present ill after international travel. METHODS: Descriptive analysis of travel-associated morbidity and mortality among US travellers seeking care at 1 of the 22 US practices and clinics participating in the GeoSentinel Global Surveillance Network from January 2000 to December 2012. RESULTS: Of the 9624 ill US travellers included in the analysis, 3656 (38%) were tourist travellers, 2379 (25%) missionary/volunteer/research/aid workers (MVRA), 1580 (16%) travellers visiting friends and relatives (VFRs), 1394 (15%) business travellers and 593 (6%) student travellers. Median (interquartile range) travel duration was 20 days (10-60 days). Pre-travel advice was sought by 45%. Hospitalization was required by 7%. Compared with other groups of travellers, ill MVRA travellers returned from longer trips (median duration 61 days), while VFR travellers disproportionately required higher rates of inpatient care (24%) and less frequently had received pre-travel medical advice (20%). Illnesses of the gastrointestinal tract were the most common (58%), followed by systemic febrile illnesses (18%) and dermatologic disorders (17%). Three deaths were reported. Diagnoses varied according to the purpose of travel and region of exposure. CONCLUSIONS: Returning ill US international travellers present with a broad spectrum of travel-associated diseases. Destination and reason for travel may help primary health care providers to generate an accurate differential diagnosis for the most common disorders and for those that may be life-threatening.

Acute muscular sarcocystosis: an international investigation among ill travelers returning from Tioman Island, Malaysia, 2011-2012.

BACKGROUND: Through 2 international traveler-focused surveillance networks (GeoSentinel and TropNet), we identified and investigated a large outbreak of acute muscular sarcocystosis (AMS), a rarely reported zoonosis caused by a protozoan parasite of the genus Sarcocystis, associated with travel to Tioman Island, Malaysia, during 2011-2012. METHODS: Clinicians reporting patients with suspected AMS to GeoSentinel submitted demographic, clinical, itinerary, and exposure data. We defined a probable case as travel to Tioman Island after 1 March 2011, eosinophilia (>5%), clinical or laboratory-supported myositis, and negative trichinellosis serology. Case confirmation required histologic observation of sarcocysts or isolation of Sarcocystis species DNA from muscle biopsy. RESULTS: Sixty-eight patients met the case definition (62 probable and 6 confirmed). All but 2 resided in Europe; all were tourists and traveled mostly during the summer months. The most frequent symptoms reported were myalgia (100%), fatigue (91%), fever (82%), headache (59%), and arthralgia (29%); onset clustered during 2 distinct periods: "early" during the second and "late" during the sixth week after departure from the island. Blood eosinophilia and elevated serum creatinine phosphokinase (CPK) levels were observed beginning during the fifth week after departure. Sarcocystis nesbitti DNA was recovered from 1 muscle biopsy. CONCLUSIONS: Clinicians evaluating travelers returning ill from Malaysia with myalgia, with or without fever, should consider AMS, noting the apparent biphasic aspect of the disease, the later onset of elevated CPK and eosinophilia, and the possibility for relapses. The exact source of infection among travelers to Tioman Island remains unclear but needs to be determined to prevent future illnesses.

Preferences and decision needs of Boston-area travelers to countries with risk of Yellow fever virus transmission: implications for health care providers.

BACKGROUND: Yellow fever (YF), a potentially fatal mosquito-borne infection, is preventable with a live-attenuated vaccine, rarely associated with severe adverse events. We surveyed travelers to assess their reasons for pre-travel medical consultation, information they considered important regarding YF disease and vaccination, whether they recalled receiving this information, and whether they were involved in vaccine decision-making. METHODS: Travelers aged 18 years and older were surveyed at three Boston-area travel clinics. Only those making YF vaccination decisions were included for analyses. RESULTS: Of 831 travelers surveyed, 589 (70%) indicated making a YF vaccination decision. Travel medicine providers recommended YF vaccination to 537 (91%) of 589 travelers; 92% of these 537 received vaccine. Among 101 travelers aged 60 years and older, 9% declined the vaccine; among those younger than 60 years, 4% declined the vaccine (p = 0.06). Of 589 travelers, most agreed they needed to understand destination-specific YF risks (82%) and vaccine risks (88%), and were involved in YF vaccine decisions (87%). Less than half recalled discussing their concerns about YF vaccine with the provider (42%) or what risks and benefits mattered most to them (32%). CONCLUSION: Most participants sought YF disease and vaccine risk information and wanted to be involved in decision-making; however, fewer than half recalled discussing their opinions or concerns about YF vaccine. Providers need effective risk communication skills and the ability to elicit and respond to travelers' concerns to help them make informed, shared decisions.

Illness in travelers returned from Brazil: the GeoSentinel experience and implications for the 2014 FIFA World Cup and the 2016 Summer Olympics.

BACKGROUND: Brazil will host the 2014 FIFA World Cup and the 2016 Olympic and Paralympic Games, events that are expected to attract hundreds of thousands of international travelers. Travelers to Brazil will encounter locally endemic infections as well as mass event-specific risks. METHODS: We describe 1586 ill returned travelers who had visited Brazil and were seen at a GeoSentinel Clinic from July 1997 through May 2013. RESULTS: The most common travel-related illnesses were dermatologic conditions (40%), diarrheal syndromes (25%), and febrile systemic illness (19%). The most common specific dermatologic diagnoses were cutaneous larva migrans, myiasis, and tungiasis. Dengue and malaria, predominantly Plasmodium vivax, were the most frequently identified specific causes of fever and the most common reasons for hospitalization after travel. Dengue fever diagnoses displayed marked seasonality, although cases were seen throughout the year. Among the 28 ill returned travelers with human immunodeficiency virus (HIV) infection, 11 had newly diagnosed asymptomatic infection and 9 had acute symptomatic HIV. CONCLUSIONS: Our analysis primarily identified infectious diseases among travelers to Brazil. Knowledge of illness in travelers returning from Brazil can assist clinicians to advise prospective travelers and guide pretravel preparation, including itinerary-tailored advice, vaccines, and chemoprophylaxis; it can also help to focus posttravel evaluation of ill returned travelers. Travelers planning to attend mass events will encounter other risks that are not captured in our surveillance network.

Regional variation in travel-related illness acquired in Africa, March 1997-May 2011.

To understand geographic variation in travel-related illness acquired in distinct African regions, we used the GeoSentinel Surveillance Network database to analyze records for 16,893 ill travelers returning from Africa over a 14-year period. Travelers to northern Africa most commonly reported gastrointestinal illnesses and dog bites. Febrile illnesses were more common in travelers returning from sub-Saharan countries. Eleven travelers died, 9 of malaria; these deaths occurred mainly among male business travelers to sub-Saharan Africa. The profile of illness varied substantially by region: malaria predominated in travelers returning from Central and Western Africa; schistosomiasis, strongyloidiasis, and dengue from Eastern and Western Africa; and loaisis from Central Africa. There were few reports of vaccine-preventable infections, HIV infection, and tuberculosis. Geographic profiling of illness acquired during travel to Africa guides targeted pretravel advice, expedites diagnosis in ill returning travelers, and may influence destination choices in tourism.

Analyzing GeoSentinel surveillance data: a comparison of methods to explore acute gastrointestinal illness among international travelers.

GeoSentinel is a global surveillance network of travel medicine clinics that collect data from ill international travelers. Analyses have relied on proportionate morbidity calculations, but proportionate morbidity cannot estimate disease risk because healthy travelers are not included in the denominator. The authors evaluated the use of a case-control design, controlling for GeoSentinel site and date of clinic visit, to calculate a reporting odds ratio (ROR). The association between region of travel and acute gastrointestinal illness was evaluated. All analyses found that the association with acute gastrointestinal illness was greatest among those who traveled to North Africa and South-Central Asia. There was consistency in the magnitude of the ROR and proportionate morbidity ratio (PMR) in regions such as the Caribbean. However, in other regions, the matched ROR was noticeably different than the PMR. The case-control ROR may be preferred for single-disease/syndrome analytical studies using GeoSentinel surveillance data or other surveillance data.

Pre-exposure rabies vaccination among US international travelers: findings from the global TravEpiNet consortium.

BACKGROUND: People who travel to areas with high rabies endemicity and have animal contact are at increased risk for rabies exposure. We examined characteristics of international travelers queried regarding rabies vaccination during pretravel consultations at Global TravEpiNet (GTEN) practices during 2009-2010. MATERIAL AND METHODS: We performed bivariate and multivariable analyses of data collected from 18 GTEN clinics. Travel destinations were classified by strength level of rabies vaccination recommendation. RESULTS: Of 13,235 travelers, 226 (2%) reported previous rabies vaccination, and 406 (3%) received rabies vaccine at the consultation. Common travel purposes for these 406 travelers were leisure (26%), research/education (17%), and nonmedical service work (14%). Excluding the 226 who were previously vaccinated, 8070 (62%) of 13,009 travelers intended to visit one or more countries with a strong recommendation for rabies vaccination; 1675 (21%) of these 8070 intended to travel for 1 month or more. Among these 1675 travelers, 145 (9%) were vaccinated, 498 (30%) declined vaccination, 832 (50%) had itineraries that clinicians determined did not indicate vaccination, and 200 (12%) remained unvaccinated for other reasons. In both bivariate and multivariate analyses, travelers with trip durations >6 months versus 1-3 months (adjusted odds ratio [OR]=4.9 [95% confidence interval [CI] 2.1, 11.4]) and those traveling for "research/education" or to "provide medical care" (adjusted OR=5.1 [95% CI 1.9, 13.7] and 9.5 [95% CI 2.2, 40.8], respectively), compared with leisure travelers, were more likely to receive rabies vaccination. CONCLUSIONS: Few travelers at GTEN clinics received rabies vaccine, although many planned trips 1 month long or more to a strong-recommendation country. Clinicians often determined that vaccine was not indicated, and travelers often declined vaccine when it was offered. The decision to vaccinate should take into account the strength of the vaccine recommendation at the destination country, duration of stay, availability of postexposure prophylaxis, potential for exposure to animals, and likelihood of recurrent travel to high-risk destinations.

Luminescent tris(8-hydroxyquinolates) of bismuth(III).

Luminescent homoleptic bismuth(III) complexes have been synthesized by adding several functionalized 8-hydroxyquinolate ligands to bismuth(III) chloride in a 3:1 mole ratio in either ethanol or tetrahydrofuran (THF) solvent. These complexes have been characterized by single-crystal X-ray diffraction (XRD) analysis, UV-vis spectroscopy, fluorescence spectroscopy, and density functional theory (DFT) calculations to determine their structures and photophysical properties. Reversible dimerization of the mononuclear tris(hydroxyquinolate) complexes was observed in solution and quantified using UV-vis spectroscopy. The fluorescence spectra show a blue shift for the monomer compared with homoleptic aluminum(III) hydroxyquinolate compounds. Four dimeric compounds and one monomeric isomer were characterized structurally. The bismuth(III) centers in the dimers are bridged by two oxygen atoms from the substituted hydroxyquinolate ligands. The more sterically hindered quinolate complex, tris(2-(diethoxymethyl)-8-quinolinato)bismuth, crystallizes as a monomer. The complexes all exhibit low-lying absorption and emission spectral features attributable to transitions between the HOMO (π orbital localized on the quinolate phenoxide ring) and LUMO (π* orbital localized on the quinolate pyridyl ring). Excitation and emission spectra show a concentration dependence in solution that suggests that a monomer-dimer equilibrium occurs. Electronic structure DFT calculations support trends seen in the experimental results with a HOMO-LUMO gap of 2.156 eV calculated for the monomer that is significantly larger than those for the dimers (1.772 and 1.915 eV). The close face to face approach of two quinolate rings in the dimer destabilizes the uppermost occupied quinolate π orbitals, which reduces the HOMO-LUMO gap and results in longer wavelength absorption and emission spectral features than in the monomer form.

Surveillance for travel-related disease--GeoSentinel Surveillance System, United States, 1997-2011.

PROBLEM/CONDITION: In 2012, the number of international tourist arrivals worldwide was projected to reach a new high of 1 billion arrivals, a 48% increase from 674 million arrivals in 2000. International travel also is increasing among U.S. residents. In 2009, U.S. residents made approximately 61 million trips outside the country, a 5% increase from 1999. Travel-related morbidity can occur during or after travel. Worldwide, 8% of travelers from industrialized to developing countries report becoming ill enough to seek health care during or after travel. Travelers have contributed to the global spread of infectious diseases, including novel and emerging pathogens. Therefore, surveillance of travel-related morbidity is an essential component of global public health surveillance and will be of greater importance as international travel increases worldwide. REPORTING PERIOD: September 1997-December 2011. DESCRIPTION OF SYSTEM: GeoSentinel is a clinic-based global surveillance system that tracks infectious diseases and other adverse health outcomes in returned travelers, foreign visitors, and immigrants. GeoSentinel comprises 54 travel/tropical medicine clinics worldwide that electronically submit demographic, travel, and clinical diagnosis data for all patients evaluated for an illness or other health condition that is presumed to be related to international travel. Clinical information is collected by physicians with expertise or experience in travel/tropical medicine. Data collected at all sites are entered electronically into a database, which is housed at and maintained by CDC. The GeoSentinel network membership program comprises 235 additional clinics in 40 countries on six continents. Although these network members do not report surveillance data systematically, they can report unusual or concerning diagnoses in travelers and might be asked to perform enhanced surveillance in response to specific health events or concerns. RESULTS: During September 1997-December 2011, data were collected on 141,789 patients with confirmed or probable travel-related diagnoses. Of these, 23,006 (16%) patients were evaluated in the United States, 10,032 (44%) of whom were evaluated after returning from travel outside of the United States (i.e., after-travel patients). Of the 10,032 after-travel patients, 4,977 (50%) were female, 4,856 (48%) were male, and 199 (2%) did not report sex; the median age was 34 years. Most were evaluated in outpatient settings (84%), were born in the United States (76%), and reported current U.S. residence (99%). The most common reasons for travel were tourism (38%), missionary/volunteer/research/aid work (24%), visiting friends and relatives (17%), and business (15%). The most common regions of exposure were Sub-Saharan Africa (23%), Central America (15%), and South America (12%). Fewer than half (44%) reported having had a pretravel visit with a health-care provider. Of the 13,059 diagnoses among the 10,032 after-travel patients, the most common diagnoses were acute unspecified diarrhea (8%), acute bacterial diarrhea (5%), postinfectious irritable bowel syndrome (5%), giardiasis (3%), and chronic unknown diarrhea (3%). The most common diagnostic groupings were acute diarrhea (22%), nondiarrheal gastrointestinal (15%), febrile/systemic illness (14%), and dermatologic (12%). Among 1,802 patients with febrile/systemic illness diagnoses, the most common diagnosis was Plasmodium falciparum malaria (19%). The rapid communication component of the GeoSentinel network has allowed prompt responses to important health events affecting travelers; during 2010 and 2011, the notification capability of the GeoSentinel network was used in the identification and public health response to East African trypanosomiasis in Eastern Zambia and North Central Zimbabwe, P. vivax malaria in Greece, and muscular sarcocystosis on Tioman Island, Malaysia. INTERPRETATION: The GeoSentinel Global Surveillance System is the largest repository of provider-based data on travel-related illness. Among ill travelers evaluated in U.S. GeoSentinel sites after returning from international travel, gastrointestinal diagnoses were most frequent, suggesting that U.S. travelers might be exposed to unsafe food and water while traveling internationally. The most common febrile/systemic diagnosis was P. falciparum malaria, suggesting that some U.S. travelers to malarial areas are not receiving or using proper malaria chemoprophylaxis or mosquito-bite avoidance measures. The finding that fewer than half of all patients reported having made a pretravel visit with a health-care provider indicates that a substantial portion of U.S. travelers might not be following CDC travelers' health recommendations for international travel. PUBLIC HEALTH ACTION: GeoSentinel surveillance data have helped researchers define an evidence base for travel medicine that has informed travelers' health guidelines and the medical evaluation of ill international travelers. These data suggest that persons traveling internationally from the United States to developing countries remain at risk for illness. Health-care providers should help prepare travelers properly for safe travel and provide destination-specific medical evaluation of returning ill travelers. Training for health-care providers should focus on preventing and treating a variety of travel-related conditions, particularly traveler's diarrhea and malaria.