Introduction to Travel Health & the CDC Yellow Book

Travel Health

The number of people traveling internationally continues to grow. According to the World Tourism Organization, there were 1.33 billion worldwide international tourist arrivals in 2017, an increase of 88% from 2015. International arrivals increased 6% in January–April 2018 compared to the same period in 2017. In 2017, US residents made nearly 88 million trips with at least 1 night outside the United States.

The importance of protecting the health of individual travelers, as well as safeguarding the health of the communities to which they return, cannot be overstated. People travel internationally for many reasons, including tourism, business, study abroad, research, visiting friends and relatives, ecotourism, adventure, medical tourism, mission work, and international disaster response. Travelers are as unique as their itineraries, covering all age ranges and having a variety of preexisting health concerns and conditions. The infectious disease risks that travelers face are dynamic—some travel destinations have become safer, while in other areas new diseases have emerged, and other diseases have reemerged.

The risk of becoming ill or injured during international travel depends on many factors, such as the region of the world visited, a traveler’s age and health status, the length of the trip, and the diversity of planned activities. CDC provides international travel health information that covers the range of health risks travelers may face, with the aim of assisting travelers and clinicians to better understand the measures necessary to prevent illness and injury during international travel. This publication and the CDC Travelers’ Health website ( are 2 primary avenues of communicating CDC’s travel health recommendations.

Box 1-1. CDC contact information for clinicians

CDC-Info National Contact Center

All topics for clinicians and general public (English and Spanish)

  • 8 am to 8 pm Eastern, M–F: toll-free at 800-CDC-INFO (800-232-4636)
  • Email form:

CDC Emergency Operations Center

Emergency or urgent patient care assistance (Note: This line is not intended for public inquiries.)

CDC Drug Service

Distribution of special biologic agents and drugs

Chikungunya, Japanese Encephalitis, Tickborne Encephalitis, and Yellow Fever

Diagnostic testing assistance and for questions about antibody response to yellow fever vaccination

  • 8 am to 4:30 pm Mountain, M–F: 970-221-6400 (Division of Vectorborne Diseases)
  • Viral Special Pathogens Branch can also assist with tickborne encephalitis, 8:30 am to 5:30 pm Eastern, M–F: 404-639-1115
  • After hours/weekends/holidays: 770-488-7100
  • State or local health departments may be able to assist:


Diagnostic testing assistance


Diagnosis and management assistance

  • 9 am to 5 pm Eastern, M–F: 770-488-7788 or toll-free at 855-856-4713
  • Emergency consultation after hours/weekends/holidays: 770-488-7100, ask for a Malaria Branch clinician

Parasitic Diseases (Other Than Malaria)

Live Support

Evaluation and management assistance for patients suspected to have a parasitic disease

  • 8 am to 4 pm Eastern, M–F: 404-718-4745
  • Emergency consultation after hours/weekends/holidays: 770-488-7100, ask for an on-call clinician in Parasitic Diseases
  • Email:

Online Support (DPDx)

Online diagnostic assistance service for laboratorians, pathologists, and other health professionals developed and maintained by CDC’s Division of Parasitic Diseases and Malaria (DPDM)

Rickettsial Diseases

Diagnosis and management assistance

  • 8:30 am to 4:30 pm Eastern, M–F: 404-639-1075
  • Emergency consultation after hours/weekends/holidays: 770-488-7100, ask for an on-call clinician in Rickettsial Diseases

Viral Hemorrhagic Fevers


Consultation for diagnosis and reporting suspected cases in or requiring evacuation to the United States

  • 8:30 am to 5:30 pm Eastern, Eastern, M–F: 404-639-1115
  • Emergency consultation after hours/weekends/holidays: 770-488-7100


Requests for ribavirin from Valeant Pharmaceuticals through the Food and Drug Administration (FDA)

  • FDA Provider Request Line: 301-736-3400
  • Simultaneously notify Valeant at 800-548-5100, ext. 5 (domestic) or 949-461-6971 (international)

History and Roles of the Yellow Book

CDC Health Information for International Travel (“The Yellow Book”) has been a trusted resource for over 50 years. In 1967, CDC published the first Yellow Book, a small pamphlet intended to satisfy the International Sanitary Regulations requirements (1951) and later, the International Health Regulations (IHR). Adopted by the World Health Organization (WHO) in 1969 and completely revised in 2005, the IHR are designed to ensure maximum security against the international spread of diseases, with minimum interference with world travel and commerce. A copy of the current IHR and supporting information can be found on the WHO website (

In addition to reporting public health events of international concern, the United States must also inform the public about health requirements for entering or leaving other countries, such as the need to be vaccinated against yellow fever. The Yellow Book and the CDC Travelers’ Health website aim to communicate these requirements under the IHR (2005).

The Yellow Book has expanded significantly in breadth and depth over the years. It is written primarily for clinicians, including physicians, nurses, and pharmacists. Others, such as people in the travel industry, multinational corporations, missionary and volunteer organizations, and individual travelers, can also find a wealth of information here.

Authored by subject-matter experts both within and outside CDC, the guidelines presented in this book are evidence-based and supported by best practices. Internal text citations have not been included; however, a bibliography is appended to the end of each section for those interested in more detailed information. The CDC Travelers’ Health program and the CDC Foundation are pleased to partner with Oxford University Press, Inc., to publish the 2020 edition. In addition to the printed copy, a searchable, online version of the Yellow Book can be found on the CDC Travelers’ Health website (

Although this publication includes the most current information available at the time of printing, requirements and recommendations can change. Check the CDC Travelers’ Health website ( and the online Yellow Book for regularly updated information on requirements for international travel.

Contact Information for CDC

Questions, comments, and suggestions for CDC Travelers’ Health, including comments about this publication, may be made through the CDC-INFO contact center, toll-free at 800-CDC-INFO (800-232-4636) 8 am to 8 pm Eastern Time (Monday–Friday, closed on holidays) or by visiting to submit your question through an online form.

Pretravel or Posttravel Clinical Questions

The CDC is not a medical facility. Clinicians needing assistance with preparing patients for international travel should consider a referral to a travel clinic or a clinic listed on the International Society of Travel Medicine (ISTM) website (

Clinicians with posttravel health questions regarding their patients may refer to a clinic listed on the ISTM website, the American Society of Tropical Medicine and Hygiene website (, or a medical university with specialists in infectious diseases.

State and local health departments may also be useful resources.

Because of the complexity of some travel-related diseases, Box 1-1 lists contact information for providers needing clinical assistance.


  1. United Nations World Tourism Organization. UNWTO World Tourism Barometer, Vol. 16 (June 6). Madrid: United Nations World Tourism Organization; 2018 [cited 2018 Jul 12]. Available from:
  2. US Department of Commerce, Office of Travel and Tourism Industries. 2017 US Citizen Travel to International Regions. Washington, DC: US Department of Commerce; 2018 [cited 2018 Jul 12]. Available from:
  3. World Health Organization. International Health Regulations (2005). Geneva: World Health Organization; 2008 [cited 2018 Jul 12]; 2nd edition. Available from:


Phyllis E. Kozarsky, Ronnie Henry