I don't know much about backcountry medicine but doing health and safety for an oil company I learned to always ask the group for their health issues. People are reluctant to volunteer medical information like epilepsy or diabetes for fear you won't let them go along, but if you ask they understand. So if you are responsible (whatever thaT means) or just in a group and nobody else asks and you don't know everybody really well, it might be a good thing to ask.