Number of AIv RNA-positive water and fecal samples at each wetland of the California Central Valley for the three sampling periods.

aFor rRT-PCR result interpretation, we considered samples with a Ct value≤40.0 as AIv-positive.bAIv isolates include one H3N8 at SAC1 in late July, one H4N8 and two H2N3 at LDC1 in mid-August, and one H3N8 at LDC2 in mid-August in fecal samples.cSamples collected at a different wetland to that sampled previously.dPresence of cows at this wetland at sampling time.