Infectious Diseases & Health Risks: A Guide to Staying Healthy While Traveling to the USA
While travel to the United States is routine for many Japanese travelers, it's easy to overlook infectious disease and hygiene risks associated with differences in climate, endemic illnesses, and food culture. Proper health preparation is especially important for extended stays or travel to rural areas. This article, supervised by a licensed pharmacist, covers key infectious diseases to watch for, water and food safety, climate-related health risks, and practical prevention strategies for U.S. travel.
Pre-Travel Vaccinations and Infectious Disease Prevention
Recommended Vaccinations
Although the U.S. healthcare system is advanced, infectious disease patterns differ from Japan. Consider the following vaccinations before departure:
| Infectious Disease | Recommended For | Vaccine Name | Timing Before Travel |
|---|---|---|---|
| Measles | Born 1968 or later with no vaccination history, or only one prior dose | MMR (Measles, Mumps, Rubella) | At least 2 weeks |
| Influenza | Everyone, especially Sept–Dec | Influenza vaccine | Sept–Oct each year |
| Pneumococcal disease | Elderly and those with underlying conditions | PPSV23, PCV13 | At least 1 month |
| Pertussis | Adults with no booster in 10+ years | Tdap (Tetanus, Diphtheria, Pertussis) | At least 4 weeks |
| COVID-19 | Everyone | mRNA or viral vector vaccine | Check latest embassy guidelines |
Pharmacist's note The USA strongly recommends MMR vaccination. Measles outbreaks have been reported in multiple states since 2019, particularly in New York and California. If you have a record of only one prior MMR dose, consider a second booster. Confirm your vaccination history before departure.
Infectious Diseases to Watch For in the USA
Lyme Disease
Vector: Tick (Ixodes scapularis)
Endemic regions: Northeast and Midwest (New York, Pennsylvania, Vermont, etc.)
Symptoms: Circular skin rash, fever, fatigue (appearing 3–30 days after exposure)
Prevention strategies:
- Wear long sleeves and long pants during outdoor activities in wooded areas
- Use insect repellents containing 20–30% DEET
- Recommended brands: OFF! Deep Woods, Repel, Sawyer
- Check your body and clothing after outdoor exposure
- If symptoms develop, early treatment with antibiotics (doxycycline) is effective
West Nile Fever
Vector: Mosquito
Endemic regions: Throughout the USA, especially South and Midwest
Peak season: June–October
Prevention strategies:
- Use mosquito repellents containing DEET
- Avoid outdoor activities during dawn, dusk, and early evening
- Use mosquito nets in your hotel room if necessary
Zika Virus Infection
Endemic regions: Southern states including Florida and Texas
Prevention: Follow mosquito prevention measures as above
Pharmacist's note Mosquito and tick repellent products are readily available at U.S. drugstores (CVS, Walgreens) and can be purchased just before your trip. If bringing insect repellent spray from Japan, note that aerosol medical-grade repellents cannot be carried in airplane cabins—only in checked baggage.
Water Safety and Drinking Water Precautions
Water Safety in the USA
American tap water is generally safe, and major cities present minimal risk. However, some considerations apply:
| Region | Safety Rating | Notes |
|---|---|---|
| Major cities (NYC, LA, etc.) | ★★★★★ | Safe to drink directly from tap |
| Medium-sized cities | ★★★★ | Generally safe; sensitive individuals should use caution |
| Rural areas and campsites | ★★★ | Possible contamination; boiling or filtering recommended |
Causes of Traveler's Diarrhea
Diarrhea during U.S. stays typically results from excessive dietary fat and spices, or bacterial infection (such as Clostridium difficile), rather than water quality alone.
Water-Related Products to Pack
- Portable water filter: LifeStraw, Sawyer Mini (as backup)
- Oral rehydration solution: Electrolyte formulation; carry from Japan for peace of mind
- U.S. brands: Pedialyte (available at CVS, Walgreens)
- Japanese brands: OS-1, Aqua Lites
Food Safety and Gastrointestinal Health
Dietary Risks in the USA
High-Fat, High-Sodium Foods
Hamburgers, fried chicken, and pizza dominate the food landscape and can be taxing on the Japanese digestive system.
Prevention strategies:
- Avoid heavy, greasy meals from day one
- Deliberately choose salads, steamed vegetables, and grilled items
- Request cooking method modifications at restaurants (e.g., "Please grill instead of fry")
Microorganism Contamination Risk
The USA permits service of raw eggs, undercooked meat and fish, and unpasteurized cheese.
Foods to avoid:
- Raw or undercooked eggs
- Rare or undercooked steak
- Raw oysters
- Undercooked chicken
Prevention strategies:
- Consume only well-cooked foods
- Avoid low-credibility restaurants
- Immunocompromised individuals (elderly, pregnant women, those with chronic illness) should be especially cautious
Over-the-Counter Medications for Gastrointestinal Issues
| Symptom | Medication | Active Ingredient | Dosing |
|---|---|---|---|
| Mild diarrhea | Loperamide (Imodium) | Loperamide HCl 2 mg | 4 mg initial dose, then 2–4 mg every 2–4 hours (max 16 mg/day) |
| Mild abdominal pain | Bismuth preparation (Pepto-Bismol) | Bismuth hydroxide | 30 mL every 4–6 hours |
| Acid reflux and digestion | Omeprazole (Prilosec) | Omeprazole 20 mg | Once daily before breakfast |
| Poor digestion | Pancreatic enzyme | Multiple enzymes | After meals |
Pharmacist's note Critical warning: Loperamide is contraindicated in diarrhea caused by Shigella, Clostridium difficile, or enterohemorrhagic E. coli. Do NOT use loperamide if you have high fever (≥39°C / 102°F), bloody stools, or severe abdominal cramps. Consult a pharmacist or physician before using loperamide in these cases. U.S. pharmacies offer free consultation services—always ask if uncertain.
How to Obtain Loperamide (Imodium)
Available without prescription at CVS, Walgreens, Target, and similar drugstores as an over-the-counter (OTC) medication.
Climate-Related Infectious Diseases and Health Risks
Regional and Seasonal Health Risks
| Region | Season | Primary Risk | Prevention |
|---|---|---|---|
| South (Florida, Texas) | Spring–Fall | Heat, humidity, heat illness, mosquito-borne diseases | Hydration, insect repellent, indoor activities |
| North (Boston, Chicago) | Winter | Extreme cold, icy roads, common cold epidemics | Warm clothing, flu vaccine |
| West (Denver, Utah) | Year-round | High altitude, low humidity, intense UV | Sunscreen, moisturizer, hydration |
| Southwest (Arizona) | Summer | Extreme heat (>40°C / 104°F), heat illness | Limit daytime outdoor activity, electrolyte supplementation |
Heat Illness Prevention
Recognizing Symptoms and Initial Response
Mild: Headache, dizziness, fatigue
Moderate: High body temperature (≥38°C / 100.4°F), muscle pain
Severe: Altered consciousness, seizures
Immediate action:
- Move immediately indoors to air-conditioned space and away from direct sun
- Drink fluids and electrolyte beverages (Gatorade, Powerade)
- Take a cool shower or apply wet towels to the body
- If symptoms persist or worsen, call 911
Preventive Medications
- Electrolyte supplements: Nuun (tablet form)
- Antiperspirant: Aluminum chlorohydroxide formulations (Degree, Secret)
Cold and Dry Climate Strategies
Winter Travel Health Management
Winter temperatures in the North can drop below –10°C (14°F).
Prevention strategies:
- Influenza vaccine: Available from Sept; Oct vaccination recommended
- Skincare: Apply ceramide-containing moisturizer (CeraVe, Cetaphil) daily
- Lip care: Use SPF-containing lip balm to prevent drying and chapping
- Humidifier: Use in hotel room to combat low humidity
Preventing Cold, Cough, and Bronchitis
Runny or stuffy nose: Decongestant nasal spray (Afrin), or oral decongestant (Sudafed, pseudoephedrine)
Cough: Guaifenesin-containing cough suppressant (Mucinex)
Sore throat: Lozenges (Cepacol), throat spray
Pharmacist's note About Pseudoephedrine: Available OTC in the USA but may require government-issued ID at purchase (due to controlled precursor regulations). Bringing your own supply from Japan poses no problem; however, quantities exceeding personal use amounts may raise concerns.
Special Considerations for Travelers with Chronic Conditions
Carrying Prescription Medications and Obtaining Refills
Bringing Prescription Medications
- Prepare an English-language prescription or physician's statement
- Record the drug name and dosage in English
- Keep medications in original containers with pharmacy labels
- Pack in checked baggage (carry-on allowances are limited)
Obtaining Medications in the USA
Japanese prescription drugs can be obtained through:
- Obtaining a new U.S. prescription (easiest option)
- International mail delivery from Japan (time-consuming)
- Obtaining a larger supply before departure (recommended)
Pharmacist's note Important: Without U.S. health insurance, physician consultations for prescriptions can cost thousands of yen. Bringing adequate supplies from Japan and avoiding clinic visits is more economical.
Health Condition-Specific Precautions
Hypertension
The American diet is high in sodium, making blood pressure management challenging.
Prevention strategies:
- Bring antihypertensive medication with a comfortable margin (3 months' supply recommended)
- Minimize high-sodium foods
- Check blood pressure at your hotel (some front desks provide portable devices)
Diabetes
American cuisine is high in sugar (soft drinks, desserts are ubiquitous), complicating glycemic control.
Prevention strategies:
- Bring adequate insulin and blood glucose monitoring supplies
- Account for pressure changes during air travel (may affect insulin stability)