Tulip mania reached its peak during the winter of 1636–37, when some bulb contracts were reportedly changing hands ten times in a day. No deliveries were ever made to fulfill any of these contracts, because in February 1637, tulip bulb contract prices collapsed abruptly and the trade of tulips ground to a halt. The collapse began in Haarlem, when, for the first time, buyers apparently refused to show up at a routine bulb auction. This may have been because Haarlem was then suffering from an outbreak of bubonic plague. The existence of the plague may have helped to create a culture of fatalistic risk-taking that allowed the speculation to skyrocket in the first place; this outbreak might also have helped to burst the bubble.