It's the season for stomach bugs again. And if you want to know just how contagious those bugs can be, just ask the National Basketball Association.
A new report from the Centers for Disease Control and Prevention gives the play-by-play on an outbreak of gastrointestinal misery that afflicted as many as 13 NBA teams a year ago, spreading rapidly from player to player and from players to team staffers.
The outbreak sickened 21 players and three staffers, and spanned 13 states.
It was caused by a norovirus, the first such outbreak of it to be documented among pro sports teams. The CDC's report, which appears in Clinical Infectious Diseases, shows what formidable foes these little buggers are. And they play dirty.
It only takes 18 noroviruses to cause an infection, the CDC researchers say. But once infected, each sick individual can shed billions of the germs into the nearby environment. And victims continue to be infectious for weeks after their symptoms go away.
Moreover, noroviruses can persist on surfaces for days or weeks, and they resist common disinfectants — including hand sanitizers. People can also get infected by breathing air containing norovirus-contaminated droplets.
"All of these factors may contribute to the rapid spread of norovirus among teammates who spend long periods together in closed spaces while in transit, during training sessions, in locker rooms, and during games," the study authors say.
The CDC investigation sussed out gastrointestinal symptoms among 400 NBA players and 378 staff members, tracking noroviruses from one infected individual to the next.
The researchers looked at a five-week period on either side of the outbreak. During that period, the 13 affected teams played 49 games against one another. None of the sick individuals reported playing while they were ill, but one vomited near teammates while traveling to a game. And as the researchers note, there were lots of opportunities to pass the virus around in locker rooms and clubhouses, on buses and planes, in hotels, and in everyday interactions.
Twenty-two percent of the cases reported "stomach flu" in their families before the first cases on their team, suggesting this is where some of the infections came from. But players on two teams reported no sickness in their households, and neither did the NBA staff members. So those cases must have come from other infected players or staffers.
All things considered, it seems remarkable that the entire NBA didn't get sick. But the study authors note some cases undoubtedly didn't get reported.
When the CDC researchers did a 10-year look-back among NBA teams, they found that gastrointestinal illness was the second most common reason for players to be out, not counting game-related injuries.
To prevent norovirus outbreaks in the future, the researchers say ill players and staffers should be isolated while they're sick and for 24 to 72 hours after they recover, "with particular focus on nongame activities." (That may be hard to enforce, given the powerful economic incentives to keep playing or return to play.)
The researchers also preach "strict personal hygiene," including frequent hand-washing with soap and water. That's better than hand sanitizers to stop the spread of noroviruses, the CDC team says.
And locker rooms and clubhouses should be disinfected regularly with a solution such as sodium hypochlorite — e.g., bleach — that's effective against the stubborn norovirus.
Those lessons are just as applicable to amateur sports teams too, of course. And although it may be impractical to disinfect your home with heavy-duty antiviral chemicals, the advice about thorough hand-washing when someone in your household is sick - and limiting contact with the ill person when possible - isn't just for professional basketball players.
And athletes are the only people at risk - norovirus gained its notorious reputation over the past decade by being the bane of cruise ship life.