Researchers have studied the link between weather patterns and influenza outbreaks. In temperate zones, flu outbreaks tend to coincide with times when temperatures drop and the air gets drier. In warmer areas, however, flu outbreaks tend to correlate with periods when the air is wet. "Nobody has a really good theory for what's going on in the tropics," said geographer James Tamerius, a postdoctoral student at Columbia University.

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