How can I stay healthy traveling?

Keep your usual... Routine and diet. Stay hydrated and get good sleep. Don't push beyond what you normally are accustomed to.
Clean hands/water. Germs are passed in two main ways. Fecal-oral and cough/inhale. Keeping your hands clean and drinking clean safe water is key. Stay hydrated and know where your food and water comes from. Public transportation is a main source of airborne infection, so be aware of enclosed spaces and stay in open air space as much as possible. Getting sleep and not overdoing activity that you are not up for.
Betaine HCL. Take betaine hcl before each meal will help kill the ingested micro-organisms - if you suspect food poisoning take 3 betaine hcl every hour until queasiness gone. Weekly do aloe cleanse drink 1 bottle of pure aloe 32oz daily x 3 days. Calm GI inflammation. Also carry medicated clay available as capsules from premium research lab - open the capsule add to 32 oz water drink this will adsorb toxins.