Swine flu riddle

The latest figures show the usual riddle of swine flu: A general decrease week-on-week in the severity of swine flu but still a leap of 25 deaths in the last week. There have now been 265 deaths (240 last week) in the UK. I've pulled out a graph of Influenza activity around England by strategic health authority (see above). It shows London, Manchester and Birmingham of course as having the most activity, presumably because of the high density population in the major cities.