If it weren't so real, so tragic, and such a Critical wake-up call, it could be a sick joke: Ricky Lannetti, 21 years old and tough as a truck tire, was killed by a pimple on his butt.

He'd noticed the little welt last fall, when he was dressing for football practice at Lycoming College in Williamsport, Pennsylvania. It was right under the back strap of his jock and getting a little raw, but he sure as hell wasn't going to ask the trainers to look at a pimple, not while other guys were waiting to have real injuries wrapped and taped.

Besides, apart from that, he felt great. As a senior and a starting wide receiver for Lycoming, Lannetti was having the best season of his life: He set a school record with 16 catches in a game, then the following week broke the record for catches in a season. The next Saturday, he snagged five balls as the Warriors won in overtime to advance in the playoffs. The next Saturday, he was dead.

What was found in Lannetti's blood was a "superbug," an especially aggressive type of bacterial infection called MRSA. Until recently, few family doctors had ever seen methicillin-resistant Staphylococcus aureus, and even fewer people had died of it. But over the past year, it has spread so quickly -- and mutated into such frighteningly powerful strains -- that even paramedics now know it by its phonetic nickname: "Mersa."

"Two years ago, it was completely unheard of," says Greg Moran, M.D., an infectious-disease specialist at the UCLA school of medicine. His E.R. has seen an "amazing" increase in MRSA cases. "Of the people who come in with skin infections, 64 percent have MRSA," he says. "It's remarkable how fast it's become one of the most common things we see."

Recent estimates by the Centers for Disease Control and Prevention (CDC) place the number of people hospitalized with MRSA annually at approximately 100,000. "The majority of the infected seem to be men," says Dr. Moran, "although no one knows why. It's such a new thing, there's not a whole lot of published information out there." So little is known about this sudden surge in MRSA cases that Dr. Moran is leading a nationwide study of skin infections seen in emergency rooms. Until then, he says, "we're learning on the fly."

Just 10 years ago, chronically ill patients in hospital settings accounted for most MRSA infections. Kidney-dialysis patients, burn victims, and HIV-AIDS sufferers were among the high-risk groups, because their immune systems were weak and they took such heavy doses of strong antibiotics that their bodies became veritable petri dishes for the growth of superbugs. And even if they weren't growing their own germs, these patients often had bedsores that allowed bacteria to worm their way in.

But now, MRSA is turning up most among the people who'd least expect to get it: young, healthy men who are often in very good shape. Last year, several members of the Miami Dolphins, including star linebacker Junior Seau and kickoff-return ace Charlie Rogers, were infected with MRSA. Seau and Rogers had to be hospitalized, as did Tampa Bay Buccaneer Kenyatta Walker and the Cleveland Browns' Ben Taylor, who needed an emergency operation to beat the infection.

It's not just pro athletes who've been hit: Five members of a fencing team in Colorado were also stricken, as were two high-school wrestlers in Indiana, 10 college football players in Pennsylvania, and two more in California. Although no quantitative studies have broken down the MRSA outbreak by gender, the CDC has found that the majority of new infections are among young men who share some kind of skin-to-skin contact, such as through sports. Outbreaks have also been reported among military recruits (235 cases were diagnosed at one basic-training site in the South), gay men, police cadets, and prisoners. All those men recovered, but many needed hospitalization and heavy antibiotics.

"You don't even need direct contact to become infected," points out Barry Kreiswirth, Ph.D., the director of the Public Health Research Institute Tuberculosis Center. "Staph has been spread in locker rooms by towel snapping. If he's got turf burn on his leg and you've got the bacteria on the towel, he can become infected."

And the more MRSA spreads, the more aggressive it seems to become. Not long ago, a person infected with staph would show up in a doctor's office with nothing worse than an abscess.

But by 1999, MRSA had killed four otherwise healthy children in North Dakota and Minnesota. By December 2003, it was strong enough to kill Ricky Lannetti.