How did Amanda Blake, Ms. Kitty of the show 'Gunsmoke,' contract the AIDS virus?

She contracted AIDS from her husband, who never told her that he had the disease.
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr and GRid=3691

Blake died on August 16, 1989, at Mercy General Hospital in Sacramento, California, of oral cancer. The exact cause of Blake’s death is unclear. It was widely reported in the news media that she had died of AIDS and had contracted HIV. According to her doctor, Sacramento, California, internist Dr. Lou Nishimura, she had throat cancer at the time of her death. Her death certificate, however, listed the immediate cause as cardiopulmonary arrest due to liver failure and CMV hepatitis.

https://en.wikipedia.org/wiki/Amanda_Blake