Shark attack expert George Burgess blames the early flurry to a mild winter that sent warm water and the sharks up the coast a few weeks earlier than usual.
"It's unusual only in a sense that bites usually don't start until mid-April. The reality is that we've had a very warm winter," said Burgess, director of the International Shark Attack File at the University of Florida.
"Sharks react to water temperatures. Temperatures are getting warmer up the coastline and that fools the sharks into thinking it's later on," he said.
He said that coincided this year with spring break for college and high school students, and Easter weekend, which for many people signals the start of the beach season.
"As simplistic as it may sound, the number of attacks depends on the number of people in the water and the number of sharks in the water. The more interaction there is, the greater the chance of an interaction turning into a bite," Burgess said.
He said murky or turbulent water limiting visibility is often a factor.
"Humans are not a normal food item, but sharks sometimes make mistakes," Burgess said. "In the attack Monday at Fort Lauderdale, Fla., the victim's arm was in motion and the shark mistook the arm as prey."
The victim was Matthew May, 29, a science teacher and YMCA swimming coach from Coldwater, Ohio, who suffered arm lacerations that will require skin grafts. His doctor expects a complete recovery.
May's injuries were the most serious of the five. The attacks ranged up Florida's east coast from Fort Lauderdale to New Smyrna Beach.
Burgess said while the number of swimmers, surfers and divers increase every year, the number of sharks bottomed out a quarter of a century ago due to over fishing. He said fishing regulations have led to a comeback but it may take 30 years to reach the levels of 1977.
Last year, there were 37 attacks in Florida, one less than the year before, despite the label of "The Summer of the Shark," in Time Magazine. Burgess said it was more of a case of "the summer of the media feeding frenzy."
The publicity was sparked by the dramatic rescue of 8-year-old Jessie Arbogast, whose arm had to be reattached after an attack near Pensacola, Fla., in July. Arbogast lost so much blood, however, he remains in a virtual coma nearly a year later.
In the United States last year there were 55 shark attack reports to 54 the previous year. Worldwide the number dropped from 85 in 2000 to 76 and the number of deaths dropped from 12 to five. There were two deaths in the United States, one in North Carolina and one in Virginia.
Burgess, however, expects the statistics to rise over the long range because of the increase human aquatic activity and better reporting of arracks from around the world.