In the paper associated with 1 it says:
The FilmArray RP test utilization rate (TUR) metric is defined as the non-normalized number of RP patient test results generated each week across the Trend sites (computed as a centered 3-week moving average). To calculate the pathogen detection rate (as displayed in Figure 2 [second data view] and on the Trend website), we compute the rate for each organism at each institution as a centered 3-week moving average. To adjust for the capacity differences between sites, a national aggregate is calculated as the unweighted average of individual site rates. Only data from sites contributing more than 30 tests per week is included to avoid noise from small numbers of tests. Because the calculation of pathogen detection rate includes results from patients with multiple detections, the detection rate for all organisms can, in theory, add up to greater than one. In practice, this does not occur.
These are rates. This does not account for testing frequency. If they only tested 1 person in the United States tomorrow, and they had rhino/entero, the graph would show 100% (obviously it wouldn't and they won't only test 1 person). That means that if testing decreased, because for example there were less patients with symptomatic viral infections, but the % positive stayed the same, the chart would not appear to change, even though there were fewer cases...
paper: https://publichealth.jmir.org/2018/3/e59/