Health officials see ‘minimal’ number of new Sonoma County coronavirus cases tied to BottleRock Napa Valley

Sonoma County Health officials said Wednesday fewer than 10 new local coronavirus cases have been tied to the recent BottleRock Napa Valley music festival, a count officials described as “minimal” considering the size of the three-day event over Labor Day weekend.

But health officials said that number likely falls short of the true number of infections, given that individuals do not always share information about gatherings they’ve attended or their source of transmission.

The popular festival drew tens of thousands of attendees to the Napa Valley Expo from Sept. 3 to 5. To mitigate potential spread of the virus, organizers required attendees to show proof of vaccination or a recent negative COVID-19 test. Masks were recommended outdoors and mandatory in indoor spaces.

Photos of the Napa Valley festival published online, showing large crowds of mostly unmasked younger people, have drawn criticisms about the potential for a “super-spreader event.”

Kathryn Pack, health program manager for Sonoma County's epidemiology team, said very few related virus cases — fewer than 10 — have so far been tied to the event.

“I would consider that to be a minimal number of cases given the large size of the event,” Pack said in an email. “However, given that individuals do not always share information with contact tracers about gatherings attended/their source of transmission, it is important to recognize that this is likely an underestimate.”

For nearly 52% of active coronavirus infections, the source of transmission is unknown, according to the latest health data. There are currently about 2,400 active coronavirus cases in the county.

According to the Centers for Disease Control and Prevention, COVID-19 symptoms may appear two to 14 days after exposure to the virus. It’s been two weeks since the event was held.

During a town hall on the COVID-19 pandemic, Pack said public health epidemiologists often see a “bump” in cases following holidays such as Labor Day, where there’s often a lot of gatherings. Pack said new coronavirus cases tied to gatherings had been declining until recently.

A month ago, Pack said, about 30% of cases — where the source of transmission is known — were tied to gatherings. That share had come down to about 13% before going back up to about 18%, she said.

“We are starting to see that go up slightly again,” she said, but she cautioned that “I don’t have the full picture of the Labor Day data or the BottleRock data to provide to you now, but that is something that we’re monitoring.”

The BottleRock festival, usually held over Memorial Day weekend, was last held in 2019. Because of the pandemic, it was postponed several times in 2020 before being pushed to 2021.

You can reach Staff Writer Martin Espinoza at 707-521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @pressreno.