Neither Biden or Sanders will be alive in November if they stay on the campaign trail.

Both are in the high risk elderly category and have serious underlying health problems (Sanders heart, Biden bood pressure (heart?)) and being on campaign trail it will be impossible to self-isolate from the SARS2 virus. Meeting with staff, public, pressing hands at fund-raisers they will be maximally exposed to social networks, it's part of the job description.

If I was a betting man I would put some money on the Democratic contender for president will NOT be Sanders or Biden, possibly someone under-60, Tulsi Gabbard? Pete Buttigieg?