A coronavirus outbreak at a rural bar in Illinois resulted in at least 46 infections, hospitalized a long-term care resident and likely spurred the temporary closure of a 650-student school, according to a new report from the Centers for Disease Control and Prevention (CDC). The findings served as a warning to businesses to enforce mask use and physical distancing, among other measures, as states loosen capacity restrictions.

"Opening up settings such as bars, where mask wearing and physical distancing are challenging, can affect the community," the CDC report reads. "As community businesses reopen, prevention measures should be emphasized, including limiting building occupancy, improving ventilation, prioritizing outdoor seating, enforcing correct mask wearing and physical distancing, staying home when ill, and encouraging COVID-19 vaccination to reduce transmission on site and within the community."

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Some attendees said there was "inconsistent mask use" and not enough physical distancing. (iStock)

The event occurred in February and was said to be a celebration of the bar’s opening. While the total number of attendees was unclear, the bar could accommodate about 100 people, the health agency wrote. The Illinois Department of Public Health was alerted of the outbreak through a state reporting system, and investigated the outbreak with local health officials, per the CDC.

Study authors described the indoor event as having "no outside air flow," and attendees "reported inconsistent mask use and not maintaining ≥6 ft of physical distance." Of the 46 reported cases, 26 infections cropped up among bar patrons, three occurred among staff, and 17 were listed as "secondary cases," or contacts who didn’t attend the event. Officials noted one asymptomatic attendee had a confirmed positive COVID-19 diagnosis the day before the event.

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Of those who attended the event and were infected, only one person was vaccinated, and since this person received just one dose five days prior, they tested positive as well; it takes time for the immune system to ramp up protection. People are considered fully vaccinated two weeks after their second dose of the Pfizer or Moderna vaccines, or two weeks after their Johnson & Johnson vaccine. 

One attendee who contracted the virus went on to list 26 close contacts, like sports teammates and those in in-person classes. Two athletes were diagnosed with COVID-19 over a week later, and officials were also alerted to the school's two-week closure on February 18 because over a dozen staff members were in isolation or quarantine, or had a family member in quarantine.

Further, one person at a long-term care facility was sent to the hospital after someone who attended the celebration and worked at the facility tested positive. The hospitalized individual was discharged on the same day, per the report. Of note, all of the facility residents and employees who came down with infections were previously offered vaccinations but none accepted. Three secondary cases were reported at the facility.

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The outbreak sent the county’s case incidence soaring; the document notes the 7-day average daily incidence doubled from about 42 cases per 100,000 people prior to the event, to over 80 cases per 100,000 people two weeks after the event.

The CDC noted the total case count is likely an underestimate due to incomplete testing and, contact tracing may have missed some infections. Other limitations included voluntary interviews among "reluctant" community members, and lacking data on variants; samples weren’t available for sequencing so no association could be made about the increase in county-level transmission and potential variants.

The CDC ultimately advised businesses to work with local health officials to tamp down infection risk that can go on to affect the community.

"Businesses can work with local health officials to promote behaviors and maintain environments that reduce the risk for SARS-CoV-2 transmission and develop strategies for reopening safely to prevent outbreaks in the community, such as modifying layouts and operating procedures," report authors wrote.