Fig. 3.

Relationship of mean temperature to respiratory syncytial virus (RSV) activity in five North American cities. The vertical axis reflects the number of RSV cases identified each week during each year of surveillance at the five study sites that provided weekly RSV totals. The horizontal axis represents the weekly average of mean daily temperatures recorded at intervals corresponding to those for which RSV totals were available. Both linear and curvilinear correlations were calculated (linear r=0·135, P=0·036; curvilinear r=0·218, P=0·021).