An overview of viral and viral-like agents in cell culture systems.

The first recognition of seriously contaminated biological products occurred almost 100 years ago. More recently, in the second half of this century, the potential for contamination by viral and viral-like agents became obvious when the SV-40 virus was identified as an endogenous agent in the cell cultures used to produce polio vaccines. The history of major contamination incidents is reviewed, and current issues are discussed.