Bismuth Subsalicylate's Role in the Prevention of Travelers' Diarrhea

Inclusion Criteria: 1. Be ≥ 18 and \<70 years of age at the time of enrollment 2. Sign an informed consent stating willingness to participate and comply with the study protocol 3. Plan on leaving for an international trip ≥7 days after their pre-travel consultation 4. Plan on traveling in country for ≥7 days but ≤21 days (21 day limit due to BSS duration recommendations and a lack of data on longer-term BSS use) 5. Traveling to either South East Asia, South Central Asia, North Africa, or Sub-Saharan Africa for at least 7 days of their itinerary 6. Be willing to complete an initial eligibility screening 7. Be willing to complete questionnaires and provide biologic specimens (stool) within 7 days of departure and within 10 days after return 8. Be willing to refrain from taking any pre-biotics, probiotic, synbiotic and/or herbal supplements throughout their study period Exclusion Criteria: 1. Are \<18 years of age or \>69 years of age 2. Are traveling in country for \<7 or \>21 days 3. Have known or suspected contraindications to taking BSS (including, but not limited to, travelers with kidney disease, diabetes, gout, a clotting disorder, or an allergy to any component of BSS) 4. Are pregnant (via self-report), are planning to become pregnant, or may become pregnant during travel (not actively using contraception and are sexually active), or are breastfeeding 5. Routinely take a medication known to interact with BSS (including, but not limited to, insulin, methotrexate, valproic acid, angiotensin-converting enzyme inhibitors, anticoagulants, or other salicylates) 6. Have taken an antibiotic in the 30 days before departure 7. Have taken any medications that may lower one's ability to fight infection (e.g., steroids, monoclonal antibodies, etc.) 8. Have previous diagnoses of immunocompromising conditions such as HIV/AIDS, complement deficiency, immunoglobulin deficiency, or undergoing active chemotherapy or participants with chronic gastrointestinal disorders, such as chronic diarrhea, irritable bowel syndrome (IBS), inflammatory bowel disease (i.e., Crohn's disease, ulcerative colitis), celiac disease, malabsorption syndromes, pancreatic insufficiency, gallbladder disease, or current gastrointestinal cancer 9. Have had diarrhea anytime in the previous 30 days, have diarrhea at the pre-travel consultation, or develop diarrhea before departure 10. Have been given doxycycline for malaria prophylaxis for the current trip (due to possible drug-drug interactions and decreased absorption of the doxycycline) 11. Have an allergy to any component of the placebo tablets