There are so many variables, it was hard to vote.
I think if one is very close to death it would be helpful for others to know. My mom died very suddenly, she was fine or so everyone thought at breakfast, went to her hotel room and died alone. I say this because it would have been so nice to say goodbye and no one got a chance.
Also, if one is seriously ill, they will most likely need help during treatment, in that case it would be impossible to keep it a secret.
But I know of someone who has a disease that is basically dormant. Not many people know about this and they prefer to keep it that way. People can treat you differently if you are sick. This person lives their life to its fullest while keeping a check on the illness. If it becomes active, then they will share due to necessity.
So, I voted that it is okay to keep it quiet because while there are many instances it is best to share there are times when keeping it to ones self allows life to go on normally as long as possible.
I live with cavemen.