TABLE 2.

Effect of pH on the infectivity of Pan-1 and poliovirus as determined by PA

Treatmenta	Pan-1		Poliovirus
	Concn (PFU/ml)	% Reduction	Concn (PFU/ml)	% Reduction
Untreated	2.8 × 107	NAc	4.5 × 108	NA
pH 9.5	1.7 × 107	39	3.6 × 108	20
pH 9.5 and then pH 3.5b	9.0 × 104	99	4.1 × 108	9

^aSamples were not treated or were treated for 30 min at different pHs and then assayed for infectious viruses by the PA. The reductions in virus titers were determined based on the numbers of PFU in the untreated samples compared with those in the treated samples. 

^bpH 9.5 and 3.5 were recommended for elution and reconcentration, respectively, of enteric viruses from water samples by the OF method. 

^cNA, not applicable.