Do I have to declare someone died in house?

Did they die in the house as a result of something wrong with the house (poison gas or something)? If the house did not cause the death, bur rather the occupant died of natural or unrelated causes, I don't see why you would need to mention it.

In my area, most houses are over 100 years old. I assume perhaps several people have died in them, but I've never been specifically told that.

Of course, I've never been asked . . . if someone asked me outright, and I knew, I probably wouldn't lie about it.

What is your concern? That people won't want to buy the home?

A seller is supposed to disclose known defects that are not obvious and issues that would have a material adverse impact on the value of the home.

The home is over an indian burial mound, the home has high radon gas problems. In otherwords those things that may be an issue and are not obvious to the "average reasonable buyer".

You do not have to disclose the home is right next to an airport or a major highway... these things are obvious.

Back to your question... Did the person pass away from normal causes? then no disclosure should be needed.

Was the deceased's death unusual or violent then maybe ... unless it was so notable that a reasonable buyer should already be aware of the issue....

Every state is different in what needs to be disclosed and what does not on some things.  You should talk with you listing agent about this and find out what there thoughts are on what you need to reveal and what you don't at this time in the disclosures.