An list with two elements of class `data.frame`
: `greece$daily`
contains a `data.frame`
with columns `date` (of class `Date`
),
`deaths` and `temperature`. `greece$weekly` contains a `data.frame`
with columns `yearweek` (integer, in YYYYWW format), `ILI` (ILI rate per
1000 patient consultations), `ppH1`, `ppH3` and `ppB` (percentage positives
for A(H1N1)pdm09, A(H3N2) and B respectively).