Fluoride and AIDS An Associated Press story

(August 25, 1998) about the lack of fluoride in most of the water supply in Utah quoted antifluoride activist Norma Sommer as claiming that fluoride may be responsible for AIDS, since the water supply in San Francisco is heavily fluoridated and that city has an unusually high incidence of AIDS. Describe how you could use this story to explain to someone who has never studied statistics that association need not imply causation.