One bar opening caused an outbreak of 46 COVID-19 infections and a school closure affecting 650 kids

• A February bar opening in rural Illinois led to at least 46 COVID-19 cases and a hospitalization.
• It also was linked to a school closure affecting 650 children.
• The case demonstrates the importance of mitigation measures as venues continue to reopen.

A February bar opening in rural Illinois led to at least 46 COVID-19 cases, a school closure affecting 650 children, and the hospitalization of one resident at a long-term care facility, a Monday report from the Centers for Disease Control and Prevention said.

One attendee had tested positive for COVID-19 the day before the event, but didn't have symptoms, while four others had COVID-19 symptoms on the day of the event, the report said.

The CDC reported that despite spaced-out tables and signs encouraging distancing and mask use, patrons didn't consistently wear masks or maintain physical distance, and the indoor venue didn't have any outdoor airflow.

The report "describes what can happen when we do not follow proper mitigation strategies when everyone is not fully vaccinated," Rochelle Walensky, the director of the CDC, said during a media briefing Monday.

Cases spread throughout the community

Officials from Illinois' health department first traced a cluster of cases to the bar event, which was mostly attended by 18- to 44-year-old white men. It's unclear how many people attended, but the venue could hold 100 people.

The state's health department investigated further, finding 46 cases linked to the event, including 26 bargoers and three staffers. One infected person had received one dose of a COVID-19 vaccine. (A single dose only offers partial immunity, and even that takes a few weeks to reach its full efficacy.)

Infected attendees then seemed to transmit the virus to at least 17 other people in the community, including 12 who lived in households with kids.

One partyer started experiencing a runny nose two days after visiting the bar, and subsequently infected two student athletes who'd been in close contact with the attendee during indoor sports practice or in-person school instruction.

Ultimately, because 13 staff members were in isolation, in quarantine, or absent because of their own child being quarantined, the school, which has 650 students, had to close for two weeks, leading to 9,100 lost days of in-person schooling.

Another bar-event attendee who worked as a nursing assistant at a long-term care facility tested positive for COVID-19 four days after the event. As a result, one other facility staffer and two residents were infected, and one resident wound up in the hospital with COVID-19 for a day. All of the infected staffers or residents had previously turned down a coronavirus vaccine.

CDC director: This event shows 'the impressive transmissibility of this virus'

The event also seemed to affect the community's COVID-19 rates more generally, with the seven-day average of daily incidence more than doubling in the two weeks afterward.

The study authors said even more people were likely infected from the event in part because interviews with public-health officials were voluntary, and many community members involved didn't want to share details about who they'd been in contact with. They added that the investigators likely missed some asymptomatic cases and their contacts.

"As we work to get more people vaccinated and as community businesses begin to reopen, these findings underscore the vast impact of a single event, affecting communities, schools, families, and fragile elderly," Walensky said.

She continued, "It emphasizes the impressive transmissibility of this virus and the continued need for layered prevention strategies, including reducing the number of people indoors, improving building ventilation, and utilizing outdoor spaces as the weather allows."