We undertook to create a mathematical model-outside the context of real foods-of the effects of pH 3, 5, 7, 9), temperature (2 & 30°C), time (days-weeks), and specific salts on the stability of enteroviruses (Salo and Cliver 1976) . PO1 was inactivated faster at any pH at 30°C than at any pH at 2°C. At pH 3, glycine-based buffer was somewhat more antiviral than phosphate-based buffer, whereas the reverse was true at pH 9. NaCl and other chloride salts accelerated PO1 inactivation at pH 3, but NaCl was much less effective at pH 4.5-7. In this era before the advent of ''molecular'' techniques, methods of demonstrating virion degradation were relatively unsophisticated. Loss of RNA infectivity appeared to accompany loss of infectivity of the virion, except at pH 3 in the presence of MgCl 2 . Susceptibility of the virus to RNase or to chymotrypsin was tested with radioactively labeled virus ( 32 P in the RNA or 14 C-leucine in the capsid) and trichloracetic acid (TCA) precipitation. TCA precipitates large molecules nonspecifically; so if the radionuclide of interest was soluble in the presence of TCA, the molecule from which it derived had been degraded. RNA hydrolysis was found to have occurred in PO1 at pH 5 and 7; and the viral RNA became susceptible to RNase in virus inactivated at pH 3, 5, 6, and 7. Only virus inactivated at pH 3 became sensitive to chymotrypsin. Echovirus 7 (EC7) has the fortuitous property of agglutinating human RBC (we used blood group O); although this may have nothing to do with infectivity, it seems similar to the blood group antigen affinities of norovirus (Marionneau et al. 2002) . The hemagglutinins of EC7 were destroyed during inactivation at pH 3, 4, 5, and 6; loss of hemagglutinin seemed precede loss of infectivity at pH 6 (Salo and Cliver 1976) .