Washington ? Donors of sperm, cartilage and other commonly transplanted tissues and cells must be closely checked for infectious diseases, the government said Thursday in rules that aim to tighten safety.

Donated blood and organs long have been strictly regulated. But other donated tissue — such as skin for burn victims, ligaments for knee surgery, umbilical cord blood, and sperm and eggs — are subject to less oversight.

Human tissues can carry diseases, and the way cells are handled can make the difference between a therapy that works and one that is wasted or dangerous when the cells die or are contaminated. That risk made headlines in 2002, when a 23-year-old Minnesota man died after knee surgery that used bacteria-laden cartilage.

The Food and Drug Administration on Thursday announced rules that could cut risky donations: Tissue banks must test and screen potential donors for signs of infectious diseases that render them ineligible.

The new rules require tissue banks to test donors and donated tissue for the AIDS virus, hepatitis B and C, syphilis and Creutzfeldt-Jakob disease, the human form of mad cow disease.

The donor testing rule will go into effect in a year, at the same time the processing standards take effect, FDA officials said.