At UC, we had cell cultures and a variety of viruses obtained from the Viral and Rickettsial Registry of the American Type Culture Collection and from colleagues. The focus was on enteroviruses, but our first published method for virus detection in cell culture was done with reovirus type 3 (RE3) (Gibbs and Cliver 1965) . Reoviruses were newly identified and perceived as a threat to human health at the time. The method of detection in cell culture was based on staining the infected cells (on a coverslip from a Leighton tube) with acridine orange, which associates with nucleic acids and fluoresces red-orange with single-stranded nucleic acids and yellow-green with double-stranded nucleic acids. RE3 infection tended to cause the host cells to spread to larger-than-usual proportions in the monolayer; viral inclusions formed in the cytoplasm and fluoresced yellow-green (because reoviral RNA is double-stranded) against the orange fluorescence of the rest of the cytoplasm. With careful scanning on a fluorescence microscope, a single infected cell could be detected on a coverslip. The principal drawback of the method was tedium. Some preliminary concentration methods were also explored: adsorption to and elution from bovine RBC, dialysis against polyethylene glycol, and preparative ultracentrifugation. Adsorption to bovine RBC is unique to RE3; the other methods found broader applications and will be discussed in the next section.