Scientists and health officials are able to track flu outbreaks
down to the county and determine much about an outbreak's
severity and how the virus is spreading. But there's still much
that's unknown about influenza. Here are three things we still
don't know about the flu: When flu seasons begin and end.
Seasonal flu activity can begin as early as October and continue
to occur as late as May, according to the Centers for Disease
Control and Prevention. The average flu season lasts for 12
consecutive weeks, or three months. The 2011-2012 flu season
began late and was relatively mild, with cases remaining low
through February. In early December 2012, Dr. Thomas Frieden,
CDC director, told reporters an increase in cases suggested flu
season had begun. "This is the earliest regular flu season we've
had in nearly a decade, since the 2003-2004 flu season," he
said. However, every flu season is different. When flu cases
peak. Generally, flu activity peaks in January or February, but
there are variations. For instan