'Combined' sums the per-100k admission rates of whichever of the three viruses reported that month, so before flu/RSV reporting began it tracks COVID alone. Winter peaks (the 'tripledemic') stack up from 2023-24 on. Grey = no reporting that month. Hospital reporting was voluntary before it became mandatory on Nov 1 2024 (and RSV/flu were added after COVID), so earlier months have thinner coverage. The colour scale is fixed per series across all months, so colours are comparable as you slide through time.