Table 2. Seasonal metrics of A(H3N2) epidemic dynamics.
Epidemic metrics are defined and labeled by which outcome category they represent.
| Epidemic Outcome | Definition | Outcome category | Citations |
|---|---|---|---|
| Epidemic size | Cumulative weekly incidence | Burden | |
| Peak incidence | Maximum weekly incidence | Burden | |
| Maximum time-varying effective reproduction number, | The number of secondary cases arising from a symptomatic index case, assuming conditions remain the same | Transmissibility | Scott et al., 2021; Bhatt et al., 2023 |
| Epidemic intensity | Inverse Shannon entropy of the weekly incidence distribution (i.e. the spread of incidence across the season) | Sharpness of the epidemic curve | Dalziel et al., 2018 |
| Subtype dominance | The proportion of influenza positive samples typed as A(H3N2) | Viral activity | |
| Excess pneumonia and influenza mortality attributable to A(H3N2) virus | Mortality burden in excess of a seasonally adjusted baseline | Severity | Hansen et al., 2022; Simonsen and Viboud, 2012 |
| Onset week | Winter changepoint in incidence | Timing | Charu et al., 2017 |
| Peak week | First week of maximum incidence | Timing | |
| Spatiotemporal synchrony | Regional variation (s.d.) in onset or peak timing | Speed | Viboud et al., 2006 |
| Onset to peak | Number of days between onset week and peak week | Speed | |
| Seasonal duration | Number of weeks with non-zero incidence | Speed |