Travel health risks range from common travelers’ diarrhea to mosquito-borne disease, vaccine-preventable infections, blood clots, and injury. The figures below show how often selected risks occur, who is most affected, and how timing, destination, and preventive care change the picture.
Table of contents
- Pre-travel care and common illness
- Malaria, dengue, and yellow fever
- Cruise and air travel health
- Mental health during travel
- Injury and death risks
- Measles and travel-related protection
Pre-travel care and common illness
Last-minute travel is common enough to matter in travel medicine. Some reports suggest that last-minute travelers make up as much as 16% of a travel clinic population. The CDC Yellow Book: Last-Minute Travelers defines a last-minute traveler as someone leaving on short notice, typically within 2 weeks. CDC encourages travelers to seek pre-travel care at least 1 month before departure, but last-minute travelers typically have time for only one pre-travel encounter.
Limited time does not eliminate every preventive option. The CDC Yellow Book: Last-Minute Travelers lists seven single-dose protection vaccines that may be relevant for last-minute travelers: hepatitis A, influenza, meningococcal ACWY, a polio booster, injectable typhoid, tetanus-diphtheria, and cholera for selected travelers. Eligibility and destination relevance still depend on the individual trip.
Travelers’ diarrhea is one of the most frequent travel illnesses. The CDC Yellow Book: Travelers’ Diarrhea reports attack rates of 30% to 70% during a 2-week period. Duration varies by cause:
| Pattern or intervention | Reported statistic |
|---|---|
| Travelers’ diarrhea attack rate over 2 weeks | 30%–70% |
| Untreated bacterial diarrhea | Usually 3–7 days |
| Untreated viral diarrhea | Generally 2–3 days |
| Protozoal diarrhea | May persist weeks to months without treatment |
| Protozoal diarrhea frequency | 2–5 loose stools per day |
| Bismuth subsalicylate effect in Mexico studies | Approximately 50% lower incidence |
The bismuth finding comes from studies in Mexico and should not be treated as a universal estimate for every destination or traveler. For hand hygiene when soap and water are unavailable, CDC recommends sanitizer containing at least 60% alcohol. These figures describe prevention and illness patterns; they do not predict an individual traveler’s outcome.
Malaria, dengue, and yellow fever
Malaria remains a major travel-related health concern. The CDC Yellow Book: Malaria recorded 2,048 travel-associated malaria cases diagnosed in the United States and territories in 2019, compared with 602 in 2020. Among U.S. cases with a known country of acquisition in 2019, 93% were acquired in Africa, 4% in Asia, and 2% in the Caribbean and the Americas. Among U.S. civilians with malaria who reported a reason for travel, 76% were visiting friends and relatives.
The broader global burden is much larger. The WHO World malaria report 2024, as cited in the CDC Yellow Book: Malaria, estimated approximately 263 million malaria infections and approximately 597,000 deaths across 83 countries in 2023. Separately, CDC reported 10 locally acquired mosquito-transmitted malaria cases across four U.S. states in 2023. These are different measures: global estimates, travel-associated diagnoses, and locally acquired U.S. cases should not be combined.
Dengue is reported in more than 100 countries and destinations worldwide. The CDC Yellow Book: Dengue estimates 390 million DENV infections globally each year, including 96 million symptomatic cases. In the United States, 7,528 travel-related dengue cases were recorded during 2010–2021; 3,135 required hospitalization and 19 resulted in death. Travel-associated dengue cases exceeded 1,400 annually in 2019 and again during 2022–2024, compared with a previous peak of 919 cases in 2016. CDC notes that dengue is more of a risk in urban and residential areas than malaria.
Yellow fever risk can be severe even when the estimated illness probability is low. The CDC Yellow Book: Yellow Fever gives an incubation period of typically 3–6 days. After a brief remission of 48 hours or less, approximately 12% of infected patients progress to severe disease, and severe cases have a case-fatality rate of 30%–60%. During 1970–2015, 11 yellow fever cases were reported in travelers from the United States and Europe to West Africa or South America; eight died, a 73% fatality proportion in that small reported group.
For an unvaccinated traveler spending 2 weeks in the specified regions, CDC estimates the following risks:
| Destination and outcome | Estimated risk per 100,000 travelers |
|---|---|
| West Africa: yellow fever illness | 50 |
| West Africa: yellow fever death | 10 |
| South America: yellow fever illness | 5 |
| South America: yellow fever death | 1 |
Vaccine risks also vary by outcome and age. Since 2001, more than 100 confirmed and suspected cases of yellow fever vaccine-associated viscerotropic disease have been reported worldwide. In the United States, vaccine-associated neurotropic disease occurs at 0.8 cases per 100,000 YF-VAX doses, rising to 2.2 per 100,000 doses among people aged 60 or older. Vaccine-associated viscerotropic disease occurs at 0.3 cases per 100,000 doses overall and 1.2 per 100,000 doses among people aged 60 or older. Its case-fatality ratio is about 43%.
Cruise and air travel health
Cruise gastrointestinal illness rates declined substantially between 2006 and 2019. The CDC Yellow Book: Cruise Ship Travel reports a fall among passengers from 32.5 to 16.9 cases per 100,000 travel days, while the crew rate fell from 13.5 to 5.2 per 100,000 travel days. Crew acute gastroenteritis incidence was 26.7 per 100,000 travel days on mega ships and 29.2 per 100,000 on super-mega ships.
Legionnaires’ disease is another cruise-related concern. About 10% of Legionnaires’ disease cases reported to CDC during 2015–2016 occurred in people who had traveled during the 10 days before symptom onset. CDC recorded 35 confirmed cases associated with cruise ship exposures during that period. The travel connection is a timing and exposure statistic, not a general infection rate for cruise passengers.
Long-distance air travel is associated with venous thromboembolism, or VTE, but estimates differ by study design. The CDC Yellow Book: Deep Vein Thrombosis and Pulmonary Embolism reports absolute risks of 1 in 4,656 person-flights and 1 in 6,000 person-flights for trips longer than 4 hours in two studies. Five prospective studies of flights longer than 8 hours found an overall VTE incidence of 0.5% among low- to intermediate-risk travelers.
Some studies found that air travel might increase overall VTE risk by two to four times. Most travel-associated VTE occurs within the first 1–2 weeks after a flight, and risk returns to baseline by 8 weeks. CDC notes that flights shorter than 4 hours have negligible symptomatic VTE risk. Between 75% and 99% of people with travel-associated VTE had at least one preexisting risk factor in some studies, while one study found that 20% had at least five risk factors.
Seat position and body mass index can also change relative risk. One study found a two-fold increase in general VTE risk for window-seat travelers compared with aisle-seat travelers. Travelers with a BMI of 30 kg/m2 or higher who sat in window seats had a six-fold increase in VTE risk. For context, the estimated annual VTE incidence in the general population is 0.1%, and CDC lists increasing risk with age among long-distance travelers older than 40.
Mental health during travel
Travel-related psychiatric events are uncommon in the studies summarized by the CDC Yellow Book: Mental Health in Travelers, but the reported rates differ by population and setting. In a study of British diplomats, psychological evacuations represented 0.3% incidence overall. About 11% of all medical evacuations were psychological, 71% of psychological evacuations involved people in their 20s, and 41% were for depression.
A U.S. Foreign Service study covering 1982–1986 reported a 0.2% incidence of psychiatric evacuations; 50% of those evacuations were for substance use or affective disorder. A study of psychiatric emergencies among travelers to Hawaii found a 0.2% rate for tourists, 2% for transient travelers, and 1% for Hawaii residents used as a comparison group. Schizophrenia was the most frequent diagnosis in that study, followed by alcohol abuse, anxiety reaction, and depression.
For tourists to Jerusalem, researchers estimated psychiatric hospitalization incidence at 19.7 cases per 100,000. At least 3.5% of psychotic episodes occurred without a prior psychiatric history. Because these findings come from different populations and historical periods, the percentages should be read as study-specific measurements rather than a single worldwide travel rate.
Injury and death risks
Travel health includes injuries and violence as well as infectious disease. The CDC Yellow Book: Injury and Death During Travel identifies drowning as a leading cause of injury death among U.S. citizens visiting countries where water recreation is a major activity. It also reports approximately 475,000 global homicide deaths per year and more than 700,000 global suicide deaths per year. Violent-death rates in low- and middle-income countries are three times those in higher-income countries.
More than 68% of all homicide deaths in U.S. citizens abroad occurred in Mexico. Diving also carries a measurable fatality risk: researchers estimate about 16 deaths per 100,000 divers per year worldwide. These figures describe broad populations and activities, so they cannot be converted into a personal trip risk without information about destination, duration, behavior, and exposure.
International travel was already extensive before the SARS-CoV-2 pandemic. The CDC Yellow Book: Jet Lag Disorder records approximately 1.5 billion international arrivals in 2019. That scale helps explain why even relatively uncommon travel-associated conditions can produce substantial numbers of cases.
Measles and travel-related protection
Vaccination coverage is central to travel health because international movement can carry measles into communities with immunity gaps. CDC Measles Data & Research states that community protection requires MMR vaccination coverage above 95%. U.S. kindergarten coverage fell from 95.2% in the 2019–2020 school year to 92.5% in 2024–2025, leaving approximately 286,000 kindergartners at risk in the latter school year.
Reported U.S. measles totals changed sharply across the measured years:
| Year or period | Reported U.S. measles measure |
|---|---|
| 2019 | 1,274 cases |
| 2020 | 13 cases |
| 2021 | 49 cases |
| 2022 | 121 cases |
| 2024 | 285 cases and 16 outbreaks |
| 2025 | 2,288 cases and 48 outbreaks |
CDC reported that 69% of 2024 cases were outbreak-associated, or 198 of 285. In 2025, 90% were outbreak-associated, or 2,065 of 2,288. The page snapshot also reported 1,830 cases across 39 jurisdictions in 2026 to date, 25 new outbreaks, and 93% of cases outbreak-associated; the same snapshot listed 1,842 cases in the outbreak-associated calculation, so those snapshot figures should be treated as page-specific rather than a finalized annual total.
Among international visitors to the United States, CDC reported 16 measles cases in 2024, 25 in 2025, and 12 in 2026 to date. CDC Travel Health Notices cover four scenarios: outbreaks, sporadic cases in unusual locations, disasters with severe environmental health risks, and mass gatherings that can lead to outbreaks. Checking the relevant notice and maintaining recommended vaccination coverage are practical parts of preparing for international travel.