Explorative analysis of spatial aspects on the Swedish influenza data

The spatial aspects on the Swedish influenza data are analyzed. During the influenza period, reports on laboratory diagnosed cases and influenza-like-illness are obtained from viral and microbiological laboratories and from sentinel physicians, respectively, in different regions of Sweden. Information about the spatio-temporal patterns might give insight in the way the influenza spreads over Sweden. It might also be used in automated surveillance systems for outbreak and peak detection of the influenza. We describe the regional patterns in Swedish influenza data in different ways. Several natural hypotheses about geographical patterns are examined but can not be verified as consistent over the years. However, we find that, for a group of large cities, the outbreak of the influenza occurs at least four weeks earlier than for the rest of Sweden. The possibilities to utilize this in surveillance systems are briefly discussed.