Infectious diseases acquired by international travellers visiting the USA.

Background: Estimates of travel-related illness have focused predominantly on populations from highly developed countries visiting low- or middle-income countries, yet travel to and within high-income countries is very frequent. Despite being a top international tourist destination, few sources describe the spectrum of infectious diseases acquired among travellers to the USA. Methods: We performed a descriptive analysis summarizing demographic and travel characteristics, and clinical diagnoses among non-US-resident international travellers seen during or after travel to the USA at a GeoSentinel clinic from 1 January 1997 through 31 December 2016. Results: There were 1222 ill non-US-resident travellers with 1393 diagnoses recorded during the 20-year analysis period. Median age was 40 (range 0-86 years); 52% were female. Patients visited from 63 countries and territories, most commonly Canada (31%), Germany (14%), France (9%) and Japan (7%). Travellers presented with a range of illnesses; skin and soft tissue infections of unspecified aetiology were the most frequently reported during travel (29 diagnoses, 14% of during-travel diagnoses); arthropod bite/sting was the most frequently reported after travel (173 diagnoses, 15% after-travel diagnoses). Lyme disease was the most frequently reported arthropod-borne disease after travel (42, 4%). Nonspecific respiratory, gastrointestinal and systemic infections were also among the most frequently reported diagnoses overall. Low-frequency illnesses (<2% of cases) made up over half of diagnoses during travel and 41% of diagnoses after travel, including 13 cases of coccidioidomycosis and mosquito-borne infections like West Nile, dengue and Zika virus diseases. Conclusions: International travellers to the USA acquired a diverse array of mostly cosmopolitan infectious diseases, including nonspecific respiratory, gastrointestinal, dermatologic and systemic infections comparable to what has been reported among travellers to low- and middle-income countries. Clinicians should consider the specific health risks when preparing visitors to the USA and when evaluating and treating those who become ill.

Enabling clinicians to easily find location-based travel health recommendations-is innovation needed?

Background: The types of place names and the level of geographic detail that patients report to clinicians regarding their intended travel itineraries vary. The reported place names may not match those in published travel health recommendations, making traveler-specific recommendations potentially difficult and time-consuming to identify. Most published recommendations are at the country level; however, subnational recommendations exist when documented disease risk varies within a country, as for malaria and yellow fever. Knowing the types of place names reported during consultations would be valuable for developing more efficient ways of searching and identifying recommendations, hence we inventoried these descriptors and identified patterns in their usage. Methods: The data analyzed were previously collected individual travel itineraries from pretravel consultations performed at Global TravEpiNet (GTEN) travel clinic sites. We selected a clinic-stratified random sample of records from 18 GTEN clinics that contained responses to an open-ended question describing itineraries. We extracted and classified place names into nine types and analyzed patterns relative to common travel-related demographic variables. Results: From the 1756 itineraries sampled, 1570 (89%) included one or more place names, totaling 3366 place names. The frequency of different types of place names varied considerably: 2119 (63%) populated place, 336 (10%) tourist destination, 283 (8%) physical geographic area, 206 (6%) vague subnational area, 163 (5%) state, 153 (5%) country, 48 (1%) county, 12 (1%) undefined. Conclusions: The types of place names used by travelers to describe travel itineraries during pretravel consultations were often different from the ones referenced in travel health recommendations. This discrepancy means that clinicians must use additional maps, atlases or online search tools to cross-reference the place names given to the available recommendations. Developing new clinical tools that use geographic information systems technology would make it easier and faster for clinicians to find applicable recommendations for travelers.

International travelers with infectious diseases determined by pathology results, Centers for Disease Control and Prevention - United States, 1995-2015.

BACKGROUND: The failure to consider travel-related diagnoses, the lack of diagnostic capacity for specialized laboratory testing, and the declining number of autopsies may affect the diagnosis and management of travel-related infections. Pre- and post-mortem pathology can help determine causes of illness and death in international travelers. METHODS: We conducted a retrospective review of biopsy and autopsy specimens sent to the Infectious Diseases Pathology Branch laboratory (IDPBL) at the Centers for Disease Control and Prevention (CDC) for diagnostic testing from 1995 through 2015. Cases were included if the specimen submitted for diagnosis was from a traveler with prior international travel during the disease incubation period and the cause of illness or death was unknown at the time of specimen submission. RESULTS: Twenty-one travelers, six (29%) with biopsy specimens and 15 (71%) with autopsy specimens, met the inclusion criteria. Among the 15 travelers who underwent autopsies, the most common diagnoses were protozoal infections (7 travelers; 47%), including five malaria cases, followed by viral infections (6 travelers; 40%). CONCLUSIONS: Biopsy or autopsy specimens can assist in diagnosing infectious diseases in travelers, especially from pathogens not endemic in the U.S. CDC's IDPBL provides a useful resource for clinicians considering infectious diseases in returned travelers.

What proportion of international travellers acquire a travel-related illness? A review of the literature.

INTRODUCTION: As international travel increases, travellers may be at increased risk of acquiring infectious diseases not endemic in their home countries. Many journal articles and reference books related to travel medicine cite that between 22-64% of international travellers become ill during or after travel; however, this information is minimal, outdated and limited by poor generalizability. We aim to provide a current and more accurate estimate of the proportion of international travellers who acquire a travel-related illness. METHODS: We identified studies via PubMed or travel medicine experts, published between January 1, 1976-December 31, 2016 that included the number of international travellers acquiring a travel-related illness. We excluded studies that focused on a single disease or did not determine a rate based on the total number of travellers. We abstracted information on traveller demographics, trip specifics, study enrollment and follow-up and number of ill travellers and their illnesses. RESULTS: Of 743 studies, nine met the inclusion criteria. The data sources were from North America (four studies) and Europe (five studies). Most travellers were tourists, the most frequent destination regions were Asia and Africa, and the median trip duration ranged from 8-21 days. Six studies enrolled participants at the travellers' pre-travel consultation. All studies collected data through either extraction from the medical record, weekly diaries, or pre- and post-travel questionnaires. Data collection timeframes varied by study. Between 6-87% of travellers became ill across all studies. Four studies provided the best estimate: between 43-79% of travellers who frequently visited developing nations (e.g. India, Tanzania, and Kenya) became ill; travellers most frequently reported diarrhoea. CONCLUSION: This is the most comprehensive assessment available on the proportion of international travellers that develop a travel-related illness. Additional cohort studies would provide needed data to more precisely determine the rates of illness in international travellers. KEYWORDS: International travel, travel, illness.

Update: Temporary Total Depletion of U.S. Licensed Yellow Fever Vaccine for Civilian Travelers Addressed by Investigational New Drug Use of Imported Stamaril Vaccine.

Sanofi Pasteur, the manufacturer of the only yellow fever vaccine (YF-VAX) licensed in the United States, has announced that their stock of YF-VAX is totally depleted as of July 24, 2017. YF-VAX for civilian use will be unavailable for ordering from Sanofi Pasteur until mid-2018, when their new manufacturing facility is expected to be completed. However, YF-VAX might be available at some clinics for several months, until remaining supplies at those sites are exhausted. In anticipation of this temporary total depletion, in 2016, Sanofi Pasteur submitted an expanded access investigational new drug application to the Food and Drug Administration to allow for importation and use of Stamaril. The Food and Drug Administration accepted Sanofi Pasteur's application in October 2016.

Addressing a Yellow Fever Vaccine Shortage - United States, 2016-2017.

Recent manufacturing problems resulted in a shortage of the only U.S.-licensed yellow fever vaccine. This shortage is expected to lead to a complete depletion of yellow fever vaccine available for the immunization of U.S. travelers by mid-2017. CDC, the Food and Drug Administration (FDA), and Sanofi Pasteur are collaborating to ensure a continuous yellow fever vaccine supply in the United States. As part of this collaboration, Sanofi Pasteur submitted an expanded access investigational new drug (eIND) application to FDA in September 2016 to allow for the importation and use of an alternative yellow fever vaccine manufactured by Sanofi Pasteur France, with safety and efficacy comparable to the U.S.-licensed vaccine; the eIND was accepted by FDA in October 2016. The implementation of this eIND protocol included developing a systematic process for selecting a limited number of clinic sites to provide the vaccine. CDC and Sanofi Pasteur will continue to communicate with the public and other stakeholders, and CDC will provide a list of locations that will be administering the replacement vaccine at a later date.

Interagency and Commercial Collaboration During an Investigation of Chikungunya and Dengue Among Returning Travelers to the United States.

Public health investigations can require intensive collaboration between numerous governmental and nongovernmental organizations. We describe an investigation involving several governmental and nongovernmental partners that was successfully planned and performed in an organized, comprehensive, and timely manner with several governmental and nongovernmental partners.

Refusal of recommended travel-related vaccines among U.S. international travellers in Global TravEpiNet.

BACKGROUND: International travellers are at risk of travel-related, vaccine-preventable diseases. More data are needed on the proportion of travellers who refuse vaccines during a pre-travel health consultation and their reasons for refusing vaccines. METHODS: We analyzed data on travellers seen for a pre-travel health consultation from July 2012 through June 2014 in the Global TravEpiNet (GTEN) consortium. Providers were required to indicate one of three reasons for a traveller refusing a recommended vaccine: (1) cost concerns, (2) safety concerns or (3) not concerned with the illness. We calculated refusal rates among travellers eligible for each vaccine based on CDC recommendations current at the time of travel. We used multivariable logistic regression models to examine the effect of individual variables on the likelihood of accepting all recommended vaccines. RESULTS: Of 24 478 travellers, 23 768 (97%) were eligible for at least one vaccine. Travellers were most frequently eligible for typhoid (N = 20 092), hepatitis A (N = 12 990) and influenza vaccines (N = 10 539). Of 23 768 eligible travellers, 6573 (25%) refused one or more recommended vaccine(s). Of those eligible, more than one-third refused the following vaccines: meningococcal: 2232 (44%) of 5029; rabies: 1155 (44%) of 2650; Japanese encephalitis: 761 (41%) of 1846; and influenza: 3527 (33%) of 10 539. The most common reason for declining vaccines was that the traveller was not concerned about the illness. In multivariable analysis, travellers visiting friends and relatives (VFR) in low or medium human development countries were less likely to accept all recommended vaccines, compared with non-VFR travellers (OR = 0.74 (0.59-0.95)). CONCLUSIONS: Travellers who sought pre-travel health care refused recommended vaccines at varying rates. A lack of concern about the associated illness was the most commonly cited reason for all refused vaccines. Our data suggest more effective education about disease risk is needed for international travellers, even those who seek pre-travel advice.

Evidence-based risk assessment and communication: a new global dengue-risk map for travellers and clinicians.

BACKGROUND: International travel can expose travellers to pathogens not commonly found in their countries of residence, like dengue virus. Travellers and the clinicians who advise and treat them have unique needs for understanding the geographic extent of risk for dengue. Specifically, they should assess the need for prevention measures before travel and ensure appropriate treatment of illness post-travel. Previous dengue-risk maps published in the Centers for Disease Control and Prevention's Yellow Book lacked specificity, as there was a binary (risk, no risk) classification. We developed a process to compile evidence, evaluate it and apply more informative risk classifications. METHODS: We collected more than 839 observations from official reports, ProMED reports and published scientific research for the period 2005-2014. We classified each location as frequent/continuous risk if there was evidence of more than 10 dengue cases in at least three of the previous 10 years. For locations that did not fit this criterion, we classified locations as sporadic/uncertain risk if the location had evidence of at least one locally acquired dengue case during the last 10 years. We used expert opinion in limited instances to augment available data in areas where data were sparse. RESULTS: Initial categorizations classified 134 areas as frequent/continuous and 140 areas as sporadic/uncertain. CDC subject matter experts reviewed all initial frequent/continuous and sporadic/uncertain categorizations and the previously uncategorized areas. From this review, most categorizations stayed the same; however, 11 categorizations changed from the initial determinations. CONCLUSIONS: These new risk classifications enable detailed consideration of dengue risk, with clearer meaning and a direct link to the evidence that supports the specific classification. Since many infectious diseases have dynamic risk, strong geographical heterogeneities and varying data quality and availability, using this approach for other diseases can improve the accuracy, clarity and transparency of risk communication.

Chikungunya and Dengue Virus Infections Among United States Community Service Volunteers Returning from the Dominican Republic, 2014.

Chikungunya spread throughout the Dominican Republic (DR) after the first identified laboratory-confirmed cases were reported in April 2014. In June 2014, a U.S.-based service organization operating in the DR reported chikungunya-like illnesses among several staff. We assessed the incidence of chikungunya virus (CHIKV) and dengue virus (DENV) infection and illnesses and evaluated adherence to mosquito avoidance measures among volunteers/staff deployed in the DR who returned to the United States during July-August 2014. Investigation participants completed a questionnaire that collected information on demographics, medical history, self-reported illnesses, and mosquito exposures and avoidance behaviors and provided serum for CHIKV and DENV diagnostic testing by reverse transcription polymerase chain reaction and IgM enzyme-linked immunosorbent assay. Of 102 participants, 42 (41%) had evidence of recent CHIKV infection and two (2%) had evidence of recent DENV infection. Of the 41 participants with evidence of recent CHIKV infection only, 39 (95%) reported fever, 37 (90%) reported rash, and 37 (90%) reported joint pain during their assignment. All attended the organization's health trainings, and 89 (87%) sought a pretravel health consultation. Most (∼95%) used insect repellent; however, only 30% applied it multiple times daily and < 5% stayed in housing with window/door screens. In sum, CHIKV infections were common among these volunteers during the 2014 chikungunya epidemic in the DR. Despite high levels of preparation, reported adherence to mosquito avoidance measures were inconsistent. Clinicians should discuss chikungunya with travelers visiting areas with ongoing CHIKV outbreaks and should consider chikungunya when diagnosing febrile illnesses in travelers returning from affected areas.

International travellers from New Jersey: piloting a travel health module in the 2011 Behavioral Risk Factor Surveillance System survey.

BACKGROUND: In 2011, the Centers for Disease Control and Prevention and the New Jersey Department of Health used the New Jersey Behavioral Risk Factor Survey (NJBRFS), a state component of the national Behavioral Risk Factor Surveillance System (BRFSS) to pilot a travel health module designed to collect population-based data on New Jersey residents travelling internationally. Our objective was to use this population-based travel health information to serve as a baseline to evaluate trends in US international travellers. METHODS: A representative sample of New Jersey residents was identified through a random-digit-dialing method and administered the travel health module, which asked five questions: travel outside of USA during the previous year; destination; purpose; if a healthcare provider was visited before travel and any travel-related illness. Additional health variables from the larger NJBRFS were considered and included in bivariate analyses and multiple logistic regression; weights were assigned to variables to account for survey design complexity. RESULTS: Of 4029 participants, 841 (21%) travelled internationally. Top destinations included Mexico (10%), Canada (9%), Dominican Republic (6%), Bahamas (5%) and Italy (5%). Variables positively associated with travel included foreign birth, ≥$75 000 annual household income, college education and no children living in the household. One hundred fifty (18%) of 821 travellers with known destinations went to high-risk countries; 40% were visiting friends and relatives and only 30% sought pre-travel healthcare. Forty-eight (6%) of 837 responding travellers reported travel-related illness; 44% visited high-risk countries. CONCLUSIONS: Approximately one in five NJBRFS respondents travelled internationally during the previous year, a sizeable proportion to high-risk destinations. Few reported becoming ill as a result of travel but almost one-half of those ill had travelled to high-risk destinations. Population-based surveillance data on travellers can help document trends in destinations, traveller type and disease prevalence and evaluate the effectiveness of disease prevention programmmes.

Measles in the 21st Century, a Continuing Preventable Risk to Travelers: Data From the GeoSentinel Global Network.

Measles remains a risk for travelers, with 94 measles diagnoses reported to the GeoSentinel network from 2000 to 2014, two-thirds since 2010. Asia was the most common exposure region, then Africa and Europe. Efforts to reduce travel-associated measles should target all vaccine-eligible travelers, including catch-up vaccination of susceptible adults.

Differential diagnosis of illness in travelers arriving from Sierra Leone, Liberia, or Guinea: a cross-sectional study from the GeoSentinel Surveillance Network.

BACKGROUND: The largest-ever outbreak of Ebola virus disease (EVD), ongoing in West Africa since late 2013, has led to export of cases to Europe and North America. Clinicians encountering ill travelers arriving from countries with widespread Ebola virus transmission must be aware of alternate diagnoses associated with fever and other nonspecific symptoms. OBJECTIVE: To define the spectrum of illness observed in persons returning from areas of West Africa where EVD transmission has been widespread. DESIGN: Descriptive, using GeoSentinel records. SETTING: 57 travel or tropical medicine clinics in 25 countries. PATIENTS: 805 ill returned travelers and new immigrants from Sierra Leone, Liberia, or Guinea seen between September 2009 and August 2014. MEASUREMENTS: Frequencies of demographic and travel-related characteristics and illnesses reported. RESULTS: The most common specific diagnosis among 770 nonimmigrant travelers was malaria (n = 310 [40.3%]), with Plasmodium falciparum or severe malaria in 267 (86%) and non-P. falciparum malaria in 43 (14%). Acute diarrhea was the second most common diagnosis among nonimmigrant travelers (n = 95 [12.3%]). Such common diagnoses as upper respiratory tract infection, urinary tract infection, and influenza-like illness occurred in only 26, 9, and 7 returning travelers, respectively. Few instances of typhoid fever (n = 8), acute HIV infection (n = 5), and dengue (n = 2) were encountered. LIMITATION: Surveillance data collected by specialist clinics may not be representative of all ill returned travelers. CONCLUSION: Although EVD may currently drive clinical evaluation of ill travelers arriving from Sierra Leone, Liberia, and Guinea, clinicians must be aware of other more common, potentially fatal diseases. Malaria remains a common diagnosis among travelers seen at GeoSentinel sites. Prompt exclusion of malaria and other life-threatening conditions is critical to limiting morbidity and mortality. PRIMARY FUNDING SOURCE: Centers for Disease Control and Prevention.

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.

Health and safety issues for travelers attending the World Cup and Summer Olympic and Paralympic Games in Brazil, 2014 to 2016.

IMPORTANCE: Travelers from around the globe will attend the 2014 Fédération Internationale de Football Association (FIFA) World Cup and the 2016 Olympic and Paralympic Games in Brazil. Travelers to these mass gathering events may be exposed to a range of health risks, including a variety of infectious diseases. Most travelers who become ill will present to their primary care physicians, and thus it is important that clinicians are aware of the risks their patients encountered. OBJECTIVE: To highlight health and safety concerns for people traveling to these events in Brazil so that health care practitioners can better prepare travelers before they travel and more effectively diagnose and treat travelers after they return. EVIDENCE REVIEW: We reviewed both peer-reviewed and gray literature to identify health outcomes associated with travel to Brazil and mass gatherings. Thirteen specific infectious diseases are described in terms of signs, symptoms, and treatment. Relevant safety and security concerns are also discussed. FINDINGS: Travelers to Brazil for mass gathering events face unique health risks associated with their travel. CONCLUSIONS AND RELEVANCE: Travelers should consult a health care practitioner 4 to 6 weeks before travel to Brazil and seek up-to-date information regarding their specific itineraries. For the most up-to-date information, health care practitioners can visit the Centers for Disease Control and Prevention (CDC) Travelers' Health website (http://wwwnc.cdc.gov/travel) or review CDC's Yellow Book online (http://wwwnc.cdc.gov/travel/page/yellowbook-home-2014).

Possible rabies exposures in Peace Corps volunteers, 2011.

We surveyed Peace Corps Medical Officers (PCMOs) to determine the frequency of and responses to possible rabies exposures of U.S. Peace Corps volunteers (PCVs). Surveys were sent to 56 PCMOs serving in countries with moderate or high rabies vaccine recommendations from the U.S. Centers for Disease Control and Prevention (CDC), of which 38 (68%) responded. Thirty-seven PCMOs reported that, of 4,982 PCVs, 140 (3%) experienced possible rabies exposures. Of these, 125 (89%) had previously received rabies vaccination, 129 (92%) presented with adequately cleansed wounds, and 106 (76%) were deemed to require and were given post-exposure prophylaxis (PEP). Of 35 respondents, 30 (86%) reported that rabies vaccine was always accessible to PCVs in their country within 24 hours. Overall, the Peace Corps is successful at preventing and treating possible rabies exposures. However, this study identified a few gaps in policy implementation. The Peace Corps should continue and strengthen efforts to provide education, preexposure vaccination, and PEP to PCVs.

Health risks, travel preparation, and illness among public health professionals during international travel.

BACKGROUND: Few data currently exist on health risks faced by public health professionals (PHP) during international travel. We conducted pre- and post-travel health surveys to assess knowledge, attitudes, and practices (KAP), and illnesses among PHP international travelers. METHOD: Anonymous surveys were completed by PHP from a large American public health agency who sought a pre-travel medical consult from September 1, 2009, to September 30, 2010. RESULTS: Surveys were completed by 122 participants; travelers went to 163 countries. Of the 122 respondents, 97 (80%) reported at least one planned health risk activity (visiting rural areas, handling animals, contact with blood or body fluids, visiting malarious areas), and 50 (41%) reported exposure to unanticipated health risks. Of the 62 travelers who visited malarious areas, 14 (23%) reported inconsistent or no use of malaria prophylaxis. Illness during travel was reported by 33 (27%) respondents. CONCLUSIONS: Most of the PHP travelers in our study reported at least one planned health risk activity, and almost half reported exposure to unanticipated health risks, and one-quarter of travelers to malarious areas reported inconsistent or no use of malaria chemoprophylaxis. Our findings highlight that communication and education outreach for PHP to prevent travel-associated illnesses can be improved.

Pre-travel preparation of US travelers going abroad to provide humanitarian service, Global TravEpiNet 2009-2011.

We analyzed characteristics of humanitarian service workers (HSWs) seen pre-travel at Global TravEpiNet (GTEN) practices during 2009-2011. Of 23,264 travelers, 3,663 (16%) travelers were classified as HSWs. Among HSWs, 1,269 (35%) travelers were medical workers, 1,298 (35%) travelers were non-medical service workers, and 990 (27%) travelers were missionaries. Median age was 29 years, and 63% of travelers were female. Almost one-half (49%) traveled to 1 of 10 countries; the most frequent destinations were Haiti (14%), Honduras (8%), and Kenya (6%). Over 90% of travelers were vaccinated for or considered immune to hepatitis A, typhoid, and yellow fever. However, for hepatitis B, 292 (29%) of 990 missionaries, 228 (18%) of 1,298 non-medical service workers, and 76 (6%) of 1,269 medical workers were not vaccinated or considered immune. Of HSWs traveling to Haiti during 2010, 5% of travelers did not receive malaria chemoprophylaxis. Coordinated efforts from HSWs, HSW agencies, and clinicians could reduce vaccine coverage gaps and improve use of malaria chemoprophylaxis.

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.