By Philip R. Fischer, MD, DTM&H

Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN

Dr. Fischer reports no financial relationships relevant to this field of study.

SYNOPSIS: Infectious illness is common in travelers from other countries visiting the United States. Skin and soft tissue infections, respiratory infections, and gastrointestinal illness are most likely, but specific geographic illnesses such as Lyme disease also occur.

SOURCE: Stoney RJ, Esposito DH, Kozarsky P, et al. Infectious diseases acquired by international travelers visiting the USA. J Travel Med 2018;25:1-7.

Typically, travel medicine specialists are concerned with health risks to travelers leaving a home in a “developed” country and traveling to a low-resource country. However, nine of the top 10 international tourist destinations are in North America or Europe; the United States reported more than 77 million visits by international tourists in 2015 alone. Infections in travelers to the United States have not been studied extensively. Therefore, researchers participating in the GeoSentinel Network reviewed data about all nonmigrant, non-U.S.-resident international travelers who experienced an illness during or soon after a trip to the United States and who sought care in a GeoSentinel Network clinic from January 1997 through December 2016. The GeoSentinel Network includes 70 participating travel and tropical medicine clinics in 30 different countries and was created in 1995 as a collaboration between the CDC and the International Society of Travel Medicine. Data-sharing allows for dissemination about outbreaks of illnesses and facilitates research about travel-related diseases.

During the study period, there were 1,393 relevant diagnoses made in 1,222 travelers. The sick travelers had come from 63 different countries (more than half from Canada or Europe). Of the ill travelers, 82% had been traveling as tourists, and the median duration of the trip was 14 days (range, one day to seven years). Overall, 52% of travelers were female, and 9% were < 18 years of age. A total of 177 patients were seen for an illness at a GeoSentinel site in the United States during their trip. Of the ill patients, 14% had skin and soft tissue infections, 7% had an acute gastrointestinal illness, and 7% had pneumonia. Sepsis, pyelonephritis, and influenza each were seen in 2% of ill travelers. Three travelers died while still in the United States (one with pneumonia and a subsequent cardiac event, one from pulmonary embolus, and one with cancer and pre-existing peritonitis who became septic).

The study included 1,045 travelers who sought care at a GeoSentinel site after the conclusion of the U.S. travel. Among them, insect bites/stings were common (15% of diagnoses), while flu-like illness (6%), upper respiratory infection (5%), acute gastrointestinal infection (4%), and skin and soft tissue infections (4%) also were seen. Influenza and Lyme disease each were diagnosed in 4% of returned travelers. There were nearly twice as many infections diagnosed in returned travelers during 2009 than in any other study year; this coincided with a global pandemic of influenza H1N1 infection.

In addition to Lyme disease, several other specific regional diseases were identified. There were 13 cases of coccidioidomycosis, mostly from Arizona. There was one case of Zika following travel in south Florida. There were three cases of dengue fever after travel in Florida and Hawaii. Two travelers acquired West Nile virus infection in the United States. Two travelers had spotted fever rickettsiosis, and one had ehrlichiosis.


Travel-related infections are not limited to visitors to resource-limited countries. We must abolish any residual notion of “us and them” where “we” are from clean countries and “they” are at risk in dirty countries. This paper serves as a good reminder that international visitors to the United States are at risk of infections during travel, and some of these infections could have been prevented with repellent use to reduce tick and mosquito bites. In addition, recent outbreaks of Salmonella,1,2 Campylobacter,1 norovirus,2,3 Escherichia coli,2,3 and Cryptosporidium3 in the United States remind us that food, water, and hand hygiene still are important in the United States (a textbook about geographic infections is in its second edition and includes a 19-page chapter on infections in the United States).4 Even as Americans are at risk of mosquito-borne diseases when visiting Africa, international travelers are at risk of various travel-related infections in the United States.

Perhaps it is helpful to review geographical illnesses in the United States, even beyond the current report in travelers. Specifically, the following states and regions have been linked with the noted infections: Hawaii (leptospirosis, dengue fever, Angiostrongylus cantonensis), Southwest (coccidioidomycosis), Texas (dengue fever, leprosy [with armadillo contact]), Midwest (Lyme disease, babesiosis), Florida (dengue fever, Zika, chikungunya), East-Central (histoplasmosis, blastomycosis), and Northeast (Lyme disease, babesiosis). This paper also provides a good reminder to all of us who live and travel within the United States. We should avail ourselves of annual influenza vaccines. We should clean injured skin carefully, avoid close contact with people who are actively coughing and sneezing, and use insect repellent on skin exposed in areas where dengue, Zika, and Lyme disease occur. Respiratory illnesses after visits to Arizona and California could prompt consideration of coccidioidomycosis.


  1. Lanier WA, Hale KR, Geissler AL, Dewey-Mattia D. Chicken liver-associated outbreaks of campylobacteriosis and salmonellosis, United States, 2000-2016: Identifying opportunities for prevention. Foodborne Pathog Dis 2018; Sep 7. doi: 10.1089/fpd.2018.2489. [Epub ahead of print].
  2. Kambhampati AK, Marsh ZA, Hlavsa MC, et al. Prevention and control of youth camp-associated acute gastroenteritis outbreaks. J Pediatric Infect Dis Soc 2018; Aug 2. doi: 10.1093/jpids/piy068. [Epub ahead of print].
  3. Graciaa DS, Cope JR, Roberts VA, et al. Outbreaks associated with untreated recreational water - United States, 2000-2014. MMWR Morb Mortal Wkly Rep 2018;67:701-706.
  4. Petersen E, Chen LH, Schlagenhauf-Lawlor P, eds. Infectious Diseases: A Geographic Guide, 2nd edition. Wiley-Blackwell: Oxford, United Kingdom; 2017.