Are you required to disclose a death in the home when selling in Washington State?

By "required" do you mean will your buyer be able to sue you afterwards? If they can convince a jury that it was a material mis-representation, then you have to disclose it in EVERY state. By that standard, the type of death is going to matter. Old man dies peacefully in his bed -- probably not material. Grisly Ronald DeFeo "Amityville" massacre, probably material. Especially if you then go on to write a book about it and the house becomes "infamous".

See this article: https://www.nolo.com/legal-encyclopedia/selling-washington-home-what-are-my-disclosure-obligations.html

Then look at RCW 64.06.020. The place to disclose a death would be under 9.A (Other Material Facts). If you're not sure if it's material, ask your real estate agent -- they should know broadly the lean of the case law in WA. The point is you make this disclosure AFTER the contract is signed, and the buyer has a relatively short period of time in which to make objections to the deal. So in a way, including the information will protect you, but can open a can of worms if the buyer has cold feet or is going to try to push for a price concession.

No

No, most homes in the world have had someone die in them, means nothing.

It depends on the state. I searched but couldnt determine the answer but this website will tell you if you fill in the address or zip code whether or not you have to disclose a death.

Possibly not

Some people are superstitious and think if someone died in a house it might be haunted