I did a little search and it seems that full disclosure is not a requirement in the U.S. I found information from California and New York.
http://www.dos.state.ny.us/LCNS/lawbooks/re-law.html §443-a. Disclosure obligations - Once you wade through the legalese, it states that the seller in New York is not required to disclose cases of AIDS, or "the property is, or is suspected to have been, the site of a homicide, suicide or other death by accidental or natural causes, or any crime punishable as a felony. " It goes on to say that this "2. (a) No cause of action shall arise against an owner or occupant of real property, or the agent of such owner or occupant, or the agent of a seller or buyer of real property, for failure to disclose in any real estate transaction a fact or suspicion contained in subdivision one of this section. " Later it states that the buyer may request in writing a disclosure, but the seller can choose whether or not to respond.
http://www.wwlaw.com/death.htmThis site is from an attorney in California, but dates from 1996. This article states that "all material facts known to the Seller affecting the value OR desirability of the property must be disclosed." But the question is as to whether a prior death on the property does affect the value or desireability.
" Civil Code §1710.2 states that death on a property need not be disclosed if it occurred more than 3 years prior to a sale. [The statute does NOT say that a death within 3 years must be disclosed.] If a death occurs on a property within 3 years, and the circumstances of that death are material (it was a gruesome or offensive death, or affected the reputation of the property), it must be disclosed."
However, in California the seller must disclose a death on the property if the buyer asks. The attorney recommends disclosing any death less than 3 years old, to avoid any liability.
"AIDS DEATHS - Civil Code §1710.2 also absolves anyone from liability for nondisclosure of AIDS related deaths, regardless of how recently the death may have occurred."
So it seems clear that the death would have to be material to the value of the property and in that case the seller should definitely disclose if there was recently a gruesome death on the property. However, no matter what the AIDS related death does not need to be disclosed. But, if a buyer was concerned about this then he or she should ask their realtor to make sure any property under consideration is clean in this respect.