“The arrival of a new professional sports team in a city, and the commencement of play by that team, increases flu mortality in the city. The largest effect comes from a new NHL team. A new NHL team moving into a city and starting play causes an increase in weekly influenza mortality of 0.382 per 100,000 residents per flu season compared to cities with no professional sports teams. Based on the sample means on Table 1, this result represents a 24.6% increase in weekly flu mortality per 100,000 residents or a total increase of about 20 flu deaths over a year in each treated city. A new NFL team moving into a city causes an increase in annual influenza mortality rates of 0.249 per flu season, a 17% increase, equivalent to about 13 additional flu deaths over 52 weeks. A city that becomes home to a new NBA team experiences an increase in flu mortality rates of 0.066 which is a 4.7% increase. The effect of a new team on flu mortality is smallest in MLB where the entry of a new team results in an increase in flu mortality rates of 0.059 or 5.3% increase.”