It all started with an unremarkable trip to grandma’s house in 1970. But two days into the visit, something went terribly wrong. The 9-month-old grandson fell ill. First, a fever. Then, a nasty rash.

or another virus is used in a bioterrorism plot against the country, said Richard McGarvey, spokesman for the state Department of Health. While an anthrax scare put the country on alert last year, an ...