The researchers said they believe this is the first evidence that this type of flu pattern is detectable at the scale of the continental United States. The study is significant in that it suggests that the spread of an epidemic may actually be predictable to some extent -- a finding that could have important public health implications. In the map above, for instance, if there was a serious outbreak in Iowa emergency rooms, public health officials in neighboring Nebraska might be put on high alert. But there may be less of an issue for Iowa's southern neighbor Missouri, as there are fewer daily commuters between the states.
"[T]he absence of predictability is problematic for the design of containment strategies, since it suggests that the annual seasonal spread of influenza within countries is highly variable and depends heavily on chance events," authors Brooke Bozick and Leslie Real wrote.