Basketball is mind-numbingly dull to watch. But it can be mildly entertaining if players are vomiting.

A new study describes a 2010 outbreak involving several NBA teams (that’s the professionals, the ones who aren’t playing and no one notices), the first known report of a norovirus outbreak in a professional sports association.

Published in Clinical Infectious Diseases and available online, the study highlights unique circumstances for spreading this highly contagious virus among players and staff on and off the court.

Author Rishi Desai, MD, MPH, and colleagues from the Centers for Disease Control and Prevention found that as many as 13 NBA teams located in 11 different states were affected by a norovirus outbreak from November to December 2010. "We confirmed that norovirus spread within at least one team and possibly from one team to another," said Dr. Desai. "Overall, 21 players and three staff from 13 teams were affected."

Rigorous sports schedules and close interactions between athletes and staff put them at increased risk for norovirus infection, the study authors note. Athletes and staff spend a lot of time together in closed spaces—in buses and airplanes, locker rooms, and on the court. Norovirus can spread easily and quickly in such spaces — through the air and on objects and surfaces where it can be infectious for days or weeks. Infected persons can shed billions of virus particles, making it very infective. Even the best hygiene and cleaning may not get rid of the virus since it resists common disinfectants.

Teams can limit norovirus transmission by keeping ill athletes off the court during games and practice, the study suggests, and by avoiding contact with athletes and staff when they are ill and up to 24 hours after recovery. Strict personal hygiene, including handwashing with soap and water, disinfecting common spaces with a sodium hypochlorite solution, and early reporting are critical for limiting transmission.