At least a dozen students at Independence High School in Loudoun County, Virginia, have tested positive for COVID-19, after many had recently returned from a club cheerleading competition in Richmond, according to NBC Washington.

Club sports, which often involve travel, are not school-based activities, but members often go to the same school.

By all accounts, the risk of in-school transmission of coronavirus appears to be lower than the risk of spreading the virus within the community surrounding the school.

Dr. David Goodfriend, health director for Loudoun County, said the risk increases for young people and parents involved in club sports that aren’t following the social distancing and mask guidelines imposed during in-school activities.

Families often travel together, dine, and stay overnight in other cities, during the season.

“When you carpool, you’re not following 6-foot distancing,” Goodfriend told NBC Washington. “You’re having people outside your ‘bubble’ with you, for extended periods of time.'”

Travel team parent Allison Shannon said her teenaged son and daughter each play on club teams, which follow Centers for Disease Control and Prevention guidelines and coach-imposed protocols.

“We bring our own pillows, and our own sheets, and our own blankets,” Shannon told NBC Washington. “I’m Lysoling everything.”

She said families avoid eating in restaurants while traveling.

“We pack coolers full of food, and coolers full of water,” Shannon said. “We really, really try hard to limit exposure.”

Loudoun County Public Schools say close contacts were quarantined, and children who tested positive are recovering at home.