As an emergency first responder, I have a recommendation for anyone reading this thread - always (yes always) carry one of these three things with you always - 1) a foldable/lightweight CPR breath mask, 2) germ resistant gauze, or 3) regular gauze. I am not talking the bulky plastic cpr mask either, they make completely flat masks you can fold and fit into a wallet or purse. If you are unable to get such a breath mask, then germ resistant gauze will work is an ok backup. I've had to give rescue breaths, and if there is an option to not doing it skin to skin, I'll take it. Even if you don't know CPR... what if you are in a witness to someone needing CPR? At least you can help the person giving the cpr by offering the mask to protect one or both of them. You never know who has what sickness or disease....
Related topic - AEDs. I recall reading on the amtrak website quite awhile ago they have AEDs on each train. Perhaps by now they have multiple units? If YOU were confronted with a situation where you had to help someone using an AED, would you know what to do to save them? Do you know how to open one and where the pads go? If you are unfamiliar with an AED - they are very user friendly but also very intimidating due to the circumstances. All AEDs have recorded voices that tell you what to do during each step, but when you are under pressure to save someone and have never seen one before it will make you very nervous. Your local Ambulance or fire departments (vollie or paid) should offer some sort of short lesson to the public. It takes only a few minutes to learn solidly and is 100% worth it.
Edit: Grammar. Good thing my old english teachers don't read my posts.