EDITED BY
Jane N. Zuckerman, MD, FRCP, FRCPath, FFPH, FFPM, FFTM
Consultant in Travel Medicine
Honorary Senior Lecturer, UCL Medical School, University College London, UK;
Honorary Consultant, Royal Free London NHS Foundation Trust and Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK;
Adjunct Professor, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Qld, Australia
Gary W. Brunette, MD, MS, FFTM
Chief, Travelers’ Health Branch
Division of Global Migration and Quarantine
Centers for Disease Control and Prevention, Atlanta, GA, USA
Peter A. Leggat, AM, MD, PhD, DrPH, FAFPHM, FFPH, FFPM(Hon), FACTM(Hon), FFTM, FACAsM
Professor and Dean, College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Qld, Australia;
Visiting Professor, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa;
Conjoint Professor, School of Health Sciences, Faculty of Health, University of Newcastle, NSW, Australia;
Adjunct Professor, Research School of Population Health, College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, Australia
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Cover image: Globe-North America ©DNY59 (iStockphoto.com)
Michael Bagshaw, MB, BCh, MRCS, FFOM, DAvMed, DFFP, FRAeS
Visiting Professor of Aviation Medicine
Honorary Civilian Consultant Adviser in Aviation Medicine to the Army
King's College London
London, UK;
Cranfield University
Cranfield, UK
Sally S.J. Bell, MB BS, Master in Maritime Medicine
Clinical Quality Consultant
London, UK
Robert Bor, DPhil, CPsychol, CSci, FBPsS, UKCP, Reg FRAeS
Professor, Lead Consultant Clinical, Counselling and Health Psychologist
Royal Free London NHS Foundation Trust;
Director, Dynamic Change Consultants
London, UK
Gary W. Brunette, MD, MS, FFTM
Chief, Travelers' Health Branch
Division of Global Migration and Quarantine
Centers for Disease Control and Prevention
Atlanta, GA, USA
I. Dale Carroll, MD, FACOG, DTM&H, FFTM RCPS (Glasgow)
Medical Director
The Pregnant Traveler
Spring Lake, MI, USA
Ian C. Cheng, BE, BMed, DipOccEnvironHealth, DipAvMed, MPH, FAFOEM, FACAsM
Adjunct Associate Professor
College of Public Health, Medical and Veterinary Sciences
James Cook University
Townsville, Queensland, Australia;
Staff Specialist - Occupational Medicine
Royal North Shore Hospital
Sydney, NSW, Australia
Anna Cristina C. Carvalho, MD, PhD
Researcher in Public Health
Laboratory of Innovations in Therapies, Education and Bioproducts)
Oswaldo Cruz Institute, FioCruz
Rio de Janeiro, Brazil
Eilif Dahl, MD, MHA, PhD
Professor Emeritus, University of Bergen
Norwegian Centre for Maritime Medicine
Haukeland University Hospital
5021 Bergen
Norway
Claire Davies, MRCP, MRCGO, DTM&H, MFTM RCPS (Glasgow)
Medical Team Manager/Travel Health Clinician
InterHealth Worldwide
London, UK
Charles D. Ericsson, MD
Professor of Medicine and Dr. and Mrs. Carl V. Vartian Professor of Infectious Diseases;
Head, Clinical Infectious Diseases
University of Texas Medical School at Houston
Houston, TX, USA
Philip R. Fischer, MD, DTM&H
Professor of Pediatrics
Mayo Clinic
Rochester, MN, USA
Richard C. Franklin, BSc, MSocSc, PhD
Associate Professor, College of Public Health, Medical and Veterinary Sciences
James Cook University
Townsville, Queensland, Australia;
Royal Life Saving Society, Australia
David O. Freedman, MD
Professor of Medicine and Epidemiology
Division of Infectious Diseases
University of Alabama at Birmingham
Birmingham, AL, USA
Joanna Gaines, PhD, MPH
Doctoral Epidemiologist
Travelers' Health Branch
Division of Global Migration and Quarantine
Centers for Disease Control and Prevention
Atlanta, GA, USA
Mark D. Gershman, MD
Medical Epidemiologist
Travelers' Health Branch
Division of Global Migration and Quarantine
Centers for Disease Control and Prevention
Atlanta, GA, USA
Brian D. Gushulak, BSc (Hon), MD
Medical Consultant
Migration Health Consultants, Inc.
P.O. Box 463
Qualicum Beach, BC, Canada
Sean T. Hudson, MBBS, MSc, FAWM, Dip Mtn Med
General Practitioner and Honorary Consultant
Accident and Emergency
Maryport Health Centre
West Cumberland Hospital
Maryport, Cumbria, UK;
Director and Founder, Expedition Medicine
Cumbria, UK
Tomas Jelinek, MD
Medical Director
Berlin Center for Travel and Tropical Medicine
Berlin, Germany
Caroline J. Knox, MBBS MSc MRCGP
General Practitioner, Castlegate Surgery
Cockermouth, Cumbria, UK;
Founder, Expedition Medicine
Cumbria, UK
Tamar Lachish, MD
Senior Doctor, Infectious Diseases Unit and the Internal Medicine Ward
Shaare-Zedek Medical Center
Jerusalem, Israel
Ted Lankester, MA, MB, Bchir, MRCGP, FFTM, RSPSG
Director of Health Services
InterHealth Worldwide
London, UK
Regina LaRocque, MD, MPH
Co-Director, Global TravEpiNet (GTEN) Program
Massachusetts General Hospital;
Assistant Professor of Medicine, Harvard Medical School
Boston, MA, USA
Karin Leder, MBBS, FRACP, PhD, MPH, DTMH
Associate Professor, Head of Infectious Disease Epidemiology Unit
Department of Epidemiology and Preventive Medicine
School of Public Health and Preventive Medicine
Monash University
Melbourne, VIC, Australia;
Head of Travel Medicine and Immigrant Health
Royal Melbourne Hospital at the Doherty Institute for Infection and Immunity
Melbourne, VIC, Australia;
Victorian Infectious Diseases Service
Royal Melbourne Hospital
Parkville, VIC, Australia
Peter A. Leggat, AM. MD, PhD, DrPH, FAFPHM, FFPH, FFPM(Hon), FACTM(Hon), FFTM, FACAsM
Professor and Dean, College of Public Health, Medical and Veterinary Sciences
James Cook University
Townsville, Queensland, Australia;
Visiting Professor, School of Public Health, Faculty of Health Sciences
University of the Witwatersrand
Johannesburg, South Africa;
Conjoint Professor, School of Health Sciences
Faculty of Health
University of Newcastle
Newcastle, New South Wales, Australia;
Adjunct Professor, Research School of Population Health
College of Medicine, Biology and Environment
Australian National University
Canberra, ACT, Australia
Louis Loutan, MD, MPH
Professor, Division of International and Humanitarian Medicine
Department of Community Medicine and Primary Care
University Hospital of Geneva
Geneva, Switzerland
Douglas W. MacPherson, MD, MSc(CTM), FRCPC
Migration Health Consultants, Inc.
Qualicum Beach, BC, Canada;
Associate Professor, Pathology and Molecular Medicine
McMaster University
Hamilton, ON, Canada
Karen J. Marienau, MD, MPH
Medical Consultant and Advisor
St. Paul, MN, USA;
Formerly Division of Global Migration and Quarantine
US Centers for Disease Control and Prevention
Atlanta, GA, USA
Alberto Matteelli, MD
Head of Community Infection Unit
Clinic of Infectious and Tropical Diseases
Spedali Civili Hospital
University of Brescia
Brescia, Italy
Anne E. McCarthy, MD, MSc, FRCPC, DTM&H, FASTMH
Professor of Medicine, University of Ottawa;
Director, Tropical Medicine and International Health Clinic
University of Ottawa
Ottawa, Canada
Sarah L. McGuinness, MBBS, BMedSc, DTMH
Infectious Diseases Registrar
Victorian Infectious Diseases Service
Royal Melbourne Hospital
Parkville, VIC, Australia
Karl Neumann, MD, FAAP, CTM
Clinical Associate Professor of Pediatrics
Weill Medical College of Cornell University, USA;
Clinical Associate Attending Pediatrician
New York Presbyterian Hospital–Cornell Medical Center
New York, (emeritus) USA;
Attending Pediatrician
Long Island Jewish Hospital, USA;
Director
Family Travel and Immunization Clinic of Forest Hills, Queens, USA
Gilles Poumerol, MD
Medical Officer
Travel Health, Information & Communication
Global Capacities Alert & Response
World Health Organization
Geneva, Switzerland
Mark A. Read, PhD
Senior Instructor, Expedition and Wilderness Medicine
Thuringowa Central. Queensland, Australia
Gary Rhodes, PhD
Director, Center for Global Education
Graduate School of Education and Information Studies
University of California at Los Angeles
Los Angeles, CA, USA
Sara Ritchie, MBChB, MRCGP, DFFP, DTM&H, MPH, Dip Derm
Honorary Clinical Fellow in Tropical and HIV Dermatology
University College London Hospitals NHS Foundation Trust London, UK
Edward T. Ryan, MD, FACP, FIDSA, FASTMH
Co-Director, Global TravEpiNet (GTEN) Program
Director, Travelers' Advice and Immunization Center
Massachusetts General Hospital;
Professor of Medicine, Harvard Medical School;
Professor of Immunology and Infectious Diseases, Harvard School of Public Health
Boston, MA, USA
Patricia Schlagenhauf, PhD
Professor, University of Zürich Centre for Travel Medicine
Zürich, Switzerland
Eli Schwartz, MD, DTMH
Professor, Director of the Center for Geographic Medicine
The Chaim Sheba Medical Center
Tel-Hashomer, Israel;
Sackler School of Medicine
Tel-Aviv University
Tel-Aviv, Israel.
Marc T.M. Shaw, DrPH, FRGS, FRNZCGP, FFTM (ACTM), FFTM RCPS (Glasgow), DipTravMed
Adjunct Professor, College of Public Health, Medical and Veterinary Sciences
James Cook University
Townsville, Queensland, Australia;
Medical Director, WORLDWISE Travellers Health Centres
Auckland, New Zealand
David R. Shlim, MD
Medical Director
Jackson Hole Travel and Tropical Medicine
Wilson Medical Center
Wilson, WY, USA
Will Smith, MD
Medical Director, Grand Teton National Park, Teton County Search and Rescue;
Clinical Faculty, University of Washington School of Medicine;
Emergency Medicine, St. John's Medical Center
Jackson, WY, USA
Mark J. Sotir, PhD, MPH
Lead, Surveillance and Epidemiology Team
Travelers' Health Branch
Division of Global Migration and Quarantine
Centers for Disease Control and Prevention
Atlanta, GA, USA
J. Erin Staples, MD, PhD
Medical Epidemiologist
Arbovirus Disease Branch
Division of Vector Borne Diseases
Centers for Disease Control and Prevention
Fort Collins, CO, USA
Kathryn N. Suh, MD, MSc, FRCPC
Associate Professor of Medicine
University of Ottawa;
Division of infectious Diseases
University of Ottawa
Ottawa, Canada
Andrea P. Summer, MD, MSCR
Associate Professor of Pediatrics
Medical University of South Carolina
Charleston, SC, USA
Joseph Torresi, MBBS, BMedSci, FRACP, PhD
NHMRC Practitioner Fellow
Department of Microbiology and Immunology
The Peter Doherty Institute for Infection and Immunity
University of Melbourne;
Associate Professor, Department of Infectious Diseases
Austin Hospital
Melbourne, VIC, Australia
Alfons Van Gompel, MD, DTM
Specialist in Internal Medicine and Tropical Medicine
Associate Professor, Tropical Medicine
Chief Physician of the Medical Services and Travel Clinic of the Institute for Tropical Medicine
Antwerp, Belgium
Francisco Vega-López, MD, MSc, PhD, FRCP, FFTM, RCPSG
Consultant Dermatologist and Honorary Professor
University College London Hospitals NHS Foundation TrustLondon, UK
Abinash Virk, MD
Associate Professor, Internal Medicine
Mayo Medical School
Division of Infectious Diseases
Mayo Clinic
Rochester, MN, USA
Mary J. Warrell, MB BS, FRCP, FRCPath
Honorary Research Associate
Oxford Vaccine Group
University of Oxford;
Centre for Clinical Vaccinology and Tropical Medicine
Churchill Hospital
Oxford, UK
Annelies Wilder-Smith, MD, PhD
Professor in Infectious Diseases
Lee Kong Chian School of Medicine
Nanyang Technological University
Singapore
Claire S. Wong, RN, MSc, FFTM RCPS (Glasgow)
Travel Health Specialist Nurse
WORLDWISE Travellers Health Centres
Auckland, New Zealand
Jane N. Zuckerman, MD, FRCP, FRCPath, FFPH, FFPM, FFTM
Consultant in Travel Medicine;
Honorary Senior Lecturer, UCL Medical School
University College London, London, UK;
Honorary Consultant, Royal Free London NHS Foundation Trust and Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK;
Adjunct Professor, College of Public Health, Medical and Veterinary Sciences
James Cook University
Townsville, Queensland, Australia
The discipline of travel medicine continues to develop with established roots and structures worldwide. The necessity for the clinical practice of travel medicine in the prevention of ill health has never been more understood than now, with ever-increasing numbers of people traveling and criss-crossing the world alongside the potential hazards that travelers themselves may be exposed to and also the potential inherent risk to public health and populations internationally as a consequence of travel. Protecting travelers and, concomitantly, communities and populations requires the skill and expertise of travel medicine practitioners whose knowledge base is underpinned by continued professional development. Knowledge and education go hand in hand, with specialist training being an essential element, so enabling best clinical practice in a constantly evolving specialty.
The purpose of this book is to support those studying for a qualification or higher degree in travel medicine, and it is hoped that it will be used alongside and complement travel medicine reference books. This book is designed not only to support postgraduate training in the discipline but also to encourage undergraduate training in travel medicine in the curriculum of multidisciplinary healthcare training programs. It has been written in a style to complement lectures, with easily accessible information on the core topics required to enable the day-to-day clinical practice of travel medicine. Authors from different continents were chosen specifically in order to represent a range of views reflecting clinical practice and training courses that are available in different countries through the world.
It is hoped that this book will become a useful aide for those furthering their knowledge in addition to being a practical guide that will enhance the clinical practice and profile of travel medicine as a specialty. For those new to the growing discipline of travel medicine, an aspiration is that this book will stimulate interest and enthusiasm for the discipline for the next generation of travel medicine practitioners.
Jane N. Zuckerman
Gary W. Brunette
Peter A. Leggat
The Editors would like to thank Maria Khan and Oliver Walter of Wiley-Blackwell for their enthusiasm, patience, and commitment that enabled the publication of this new book in travel medicine. In addition, we would like to thank Jennifer Seward and Jasmine Chang, also of Wiley-Blackwell, for all their help in the preparation of this edition. We would also like to thank all the authors for contributing to this book and to supporting the future development of the discipline of travel medicine. In particular, we would like to thank our families for their unfailing support and understanding, specifically Eugene, Tunde, and Pan, without whom this new textbook would not have been realized.
Mark J. Sotir1 & David O. Freedman2
1Centers for Disease Control and Prevention, Atlanta, GA, USA
2University of Alabama at Birmingham, Birmingham, AL, USA
Infectious conditions comprise a substantial portion of texts and guidelines related to travel medicine [1,2]. To prescribe optimal pre-travel advice, preventive measures, and education to travelers, travel health providers must be familiar with basic epidemiologic concepts, and also the epidemiology and geographic distribution of relevant infections. As past experience may predict future risk, a traveler-specific risk assessment allows possible measures, advice, and behavior modification to be appropriately prioritized for each traveler.
During the past two decades, the most important and relevant data on travel-related disease have come from surveillance of travelers themselves. Although available Ministry of Health data based on people native to an endemic locale may reflect national or state-level trends and identify the most important diseases to monitor within a country, the risk behaviors, eating habits, accommodations, knowledge of preventive measures, and precise itineraries of travelers can differ greatly from those of local populations. The GeoSentinel surveillance system, a collaborative effort between the International Society of Travel Medicine and the US Centers for Disease Control and Prevention, maintains the largest such surveillance database, with more than 200,000 records from patients with a confirmed or probable travel-related diagnosis. GeoSentinel is a global provider-based network of travel and tropical medicine clinics, which, as of August 2013, has 57 participating clinics on six continents. Details of the standard data collection instrument, diagnostic categories, and patient classification methods used in GeoSentinel have recently been published [3]. The network also facilitates rapid communication, obtains data, and reports on unusual or newly emerging health events in travelers [3].
The most recent surveillance results on travelers published from the GeoSentinel network [4] indicate that Asia (32.6%) and sub-Saharan Africa (26.7%) were the most common regions where illnesses were acquired (Figure 1.1). Three-quarters of travel-related illness was due to gastrointestinal (34.0%), febrile (23.3%), and dermatologic (19.5%) diseases. Malaria, dengue, enteric fever, spotted-fever group rickettsioses, chikungunya, and non-specific viral syndromes remained the most important of the acute systemic febrile illnesses. Falciparum malaria was mainly acquired in West Africa, and enteric fever was largely contracted on the Indian subcontinent; leptospirosis, scrub typhus, and murine typhus were principally acquired in South-East Asia. More than two-thirds of dengue infections were acquired in Asia, mostly Thailand, Indonesia, and India; seasonality of dengue varies according to destination. Common skin and soft tissue infections, mosquito bites (often infected), and allergic dermatitis remain the most common dermatologic conditions affecting travelers; of the more exotic infections, hookworm-related cutaneous larva migrans, leishmaniasis, myiasis, and tungiasis are the most important. The relative frequency of many diseases varies with both travel destination and reason for travel, with travelers visiting friends and relatives (VFRs) in their country of origin having both a disproportionately high burden of serious febrile illness (malaria) and very low rates of seeking advice before travel (18.3%). Although the most travel-related illness seen in GeoSentinel clinics comes from Asia, the proportion of travelers who become ill enough to seek specialized care appears to be much higher in travelers returning from Africa or Latin America. Only 40.5% of all ill travelers reported pre-travel medical visits.
Figure 1.1 Presentations to GeoSentinel by diagnostic category and region (2007–2011), plus 2010 regional WTO traveler arrivals. Left vertical axis shows cumulative number of presentations to GeoSentinel sites by ill returned travelers during 2007–2011 according to syndromic presentation and region of illness acquisition. Right vertical axis (narrow gray bars) shows traveler arrivals in 2010 by region, according to WTO data. WTO, World Tourism Organization; Aust, Australia; NZ, New Zealand, N Africa, North Africa; ME, Middle East; SS Africa, sub-Saharan Africa; GU, genitourinary.
Source: Adapted from Leder et al. 2013 [4].
Regional surveillance networks such as TropNet, a consortium of European centers, have contributed additional information on large numbers of travelers with dengue, schistosomiasis, leishmaniasis, and in particular malaria [5]. Sentinel event detection has led to notifications of outbreaks of travel-related African trypanosomiasis [6], leptospirosis, and malaria that have been indicative of possible changes in destination-specific risk.
Although GeoSentinel and similar traveler surveillance networks offer many advantages over disease-specific studies or data collated at single centers, they have several limitations. The reported cases represent a sentinel convenience sample of ill returned travelers visiting specialist clinics and do not reflect the experience of healthy travelers or those with mild or self-limited illness who visit primary care practices or other healthcare sites. In addition, referral patterns, patient populations, and travel demographic characteristics are not consistent between sites. Although collecting data exclusively from ill patients does not permit absolute or relative risks to be determined, the available data do show the relative frequency and range of illnesses seen in wide samples of travelers.
Estimates of true incidence and true risk in travelers (often expressed as number of events per 100,000 travelers) have been elusive for a number of reasons. Although a number of approaches to measure risk have been discussed in detail [7], such estimates have been limited in terms of obtaining both an accurate numerator (number of cases of disease) and denominator (number of travelers overall or to a specific destination who are susceptible to infection and illness). Many travelers to a specific location who become infected or ill will have returned to their home country by the time they develop signs and symptoms, so will not be captured by surveillance in the country of exposure, even if reporting is good. Similarly, diseases with short incubation periods may have resolved by the return home and not be captured in the country of origin. A denominator for all travelers to a specific location that could be used to calculate incidence is also generally problematic, and those available are typically estimates provided only at the country or region level and not at the actual destination level [8].
Many of the cited data on incidence of infection in travelers, some of which were published more than three decades ago, are based on extrapolations of small single-site studies or limited data collected from small samples of travelers. Authoritative texts such as the 2014 US CDC Yellow Book [1] often contain tables of global risk estimates that may range from 20–40% of all travelers for travelers' diarrhea to 0.0001% for Japanese encephalitis for all travelers to Asia. Although such numbers are useful as a guide to relative disease risks in large populations, the travel advisor should always seek out the most destination-specific information possible. Unfortunately, for many diseases, such information is only available to the national or, at most, the first geographic administrative level and might apply only to native populations and not to travelers.
A number of factors are important in analyzing epidemiologic data on travel-related diseases or in interpreting published reports. First, the characteristics specific to the disease itself, such as mode of transmission (vector-borne, food-borne, water-borne, environmental exposure), incubation period, signs and symptoms, duration of illness, diagnostic testing, and importance of comorbidities in acquiring and presenting with illness, and clinical outcomes must be considered. Second, the presence, frequency, seasonality, and geographic distribution of the disease need to be assessed, and these might change over time due to outbreaks, emergence or re-emergence in new areas or populations, successful public health interventions, and other factors. Third, as discussed above, travelers represent a unique subset of individuals, hence their exposure might differ compared with that of residents of a destination country.
As a result, along with demographic characteristics, additional travel-specific variables that must be considered would be trip length, destinations (both current and previous), specific travel itineraries (if known), purpose of travel, and type of traveler; preparation before and behaviors during travel also factor into the epidemiology of travel illnesses. Some but not all of these variables are systematically collected by surveillance systems that either focus on travelers, such as GeoSentinel, or collect data on illnesses that affect travelers. In addition, travelers are a heterogeneous group, and because analyses are always composed of samples rather than entire populations, the sample profile must be carefully examined and disclosed. For example, VFRs have consistently represented higher proportions of serious febrile illness, particularly malaria, among travelers [9,10].
Data on the health characteristics and pre-travel healthcare of travelers are important to provide insight into the itinerary, purpose of travel, or existing medical conditions in order to prioritize the most relevant interventions and education. A US-based provider network, Global TravEpiNet (GTEN), systematically collects data from travelers presenting to a consortium of 26 travel and tropical medicine clinics. Of 13,235 travelers seen from 2009 to 2010 in GTEN clinics, India, South Africa, and China were the most common intended destinations for these travelers, with more than one-third of trips occurring in June, July, and August [11]. Travelers seen in sampled GTEN clinics ranged in age from 1 month to 94 years, with a median of 35 years. The median duration of travel was 14 days, although 22% of travelers pursued trips of >28 days, and 3% of travelers pursued trips of >6 months. About 75% were traveling to malaria-endemic countries; of the 72% who were prescribed an antimalarial, 70% of the prescriptions were for atovaquone/proguanil. Of the 87% of travelers who were prescribed an antibiotic for presumptive self-treatment of travelers' diarrhea, a fluoroquinolone or azithromycin was prescribed in almost equal proportions. Vaccines against hepatitis A and typhoid were the most frequently administered. About 38% of travelers were visiting yellow fever-endemic countries, for which they may need a vaccine requiring a higher level of practitioner knowledge. Immunocompromising conditions, such as HIV infection and AIDS, organ transplant, or receipt of immunocompromising medications, were present in 3% of travelers. Although this is a relatively large multicenter sample, GTEN is limited to a subset of specialized travel and tropical medicine clinics in the United States and does not capture travelers who seek pre-travel care from primary care and other providers, and data have only been collected since 2009.
As travel medicine continues to grow with regard to both number of practitioners and subject matter, infectious diseases will remain an important and perhaps an even greater component of the discipline. Likewise, the epidemiology of infectious diseases in travelers will remain important, with surveillance and reporting potentially being enhanced and refined, resulting in more complete and informative data being available to both clinical and public health practitioners and allowing more informed decisions to be made with regard to protecting the health of the traveler.