Investigation and Findings
On February 17, 2021, IDPH was notified through the state’s outbreak reporting system of a possible COVID-19 outbreak (i.e., five or more cases linked to a common location) in persons who attended an opening event at a bar in a rural Illinois county. The event had occurred indoors, with no outside air flow, approximately 2 weeks earlier in a 2,800-sq-ft bar during normal operating hours (4:00 p.m. to 1:00 a.m.). Six employees staffed the bar. Although the total number of bar patrons who attended the event is unknown, the bar accommodates approximately 100 persons. Before the event, IDPH reported a 7-day average daily COVID-19 incidence of 41–42 cases per 100,000 persons in the county; 14 days after the event, the 7-day average daily incidence had more than doubled, to 86–87 cases per 100,000 persons (2). On February 12, through routine testing and contact tracing, local health department staff members identified a cluster of cases linked to the bar event, including a case in an asymptomatic attendee who received a confirmed COVID-19 diagnosis the day before the event.
A bar attendee case was defined as the onset of COVID-19–like symptoms or receipt of a positive SARS-CoV-2 test result within 14 days of the bar opening event in a bar patron or employee who reported attending the event and who had no previous identified epidemiologic link to a COVID-19 case outside that setting. A confirmed case was defined as receipt of a positive SARS-CoV-2 nucleic acid amplification test (NAAT) or antigen test result by a person who attended the event, and a probable case was defined as COVID-19–like symptoms in a person who attended the event but had no laboratory confirmation of infection.† A secondary case was defined as receipt of a positive SARS-CoV-2 NAAT or antigen test result by a close contact of a person with event-associated COVID-19.§
Local health department staff members, per standard practice, conducted case investigations within 48 hours of receipt of a positive SARS-CoV-2 test result in the county using a standardized questionnaire; demographic data, symptoms, and symptom onset date were entered into an electronic contact tracing platform. Through routine case investigation, local health department investigators identified a cluster of cases linked to the bar opening event through case reports indicating that persons attended the event or were close contacts of a person with an event-associated case during the 14 days before symptom onset or the testing date. All persons with a bar attendee case or secondary case of COVID-19 were interviewed by local health department staff members. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.¶
Bar patrons and employees. By February 16, 2021, 29 bar attendee cases had been identified among persons who reported attending the opening event (Figure), including 26 (89.7%) in bar patrons and three (10.3%) in employees; all identified cases were confirmed by NAAT or antigen testing, except one probable case in a person who had COVID-19–like symptoms but did not receive testing (Table). Three additional employees worked during the event, all of whom had received a positive test result during the preceding 90 days and had completed 10 days of isolation from symptom onset or test date. Among persons with bar attendee cases, 25 (86.2%) had symptomatic illnesses. Among persons with symptom onset after the start of the event, onset dates ranged from 1 to 7 days after the event. Four (13.8%) persons with bar attendee cases reported having symptoms on the day of the event and were not reported to be contacts of one another before the event. Event attendees reported inconsistent mask use and not maintaining ≥6 ft of physical distance, despite table spacing and signs encouraging physical distancing and mask use. Most persons with bar attendee cases were adults aged 18–44 years (75.9%), male (65.5%), and non-Hispanic White persons (79.3%). One of the 29 persons with a bar attendee case, a bar patron, had received a COVID-19 vaccination before the event (the first dose, 5 days before receipt of the positive SARS-CoV-2 test result). No other persons with bar attendee cases had received a COVID-19 vaccination.
Secondary community cases. After the bar opening event, at least 71 close contacts of persons with bar attendee COVID-19 were reported; among these, 37 (52.1%) received testing, 17 (45.9%) of whom received a positive test result within 14 days of the contact. Two persons with secondary COVID-19 cases were school-related contacts of persons with bar attendee COVID-19, three were LTCF contacts, and 12 were household contacts. Among the 17 persons with secondary cases of confirmed COVID-19, 13 were symptomatic, with symptom onset dates ranging from 3 to 11 days after the event. Median age was 28 years (range = 10–71 years), and nine persons were female.
One bar attendee with COVID-19 reported the onset of a runny nose 2 days after the event and reported 26 close contacts at school during indoor sports practice and in-person school instruction. Two student athletes who were close contacts of this person subsequently received COVID-19 diagnoses 8 and 13 days after the event. Local health department officials were notified by a school official that the school district would close for 2 weeks beginning February 18 because 13 staff members were in isolation, in quarantine, or absent because their own child was quarantined.
One bar attendee who worked at an LTCF as a certified nursing assistant was asymptomatic and received a positive test result during routine COVID-19 testing at the facility 4 days after the event. After receipt of the positive test result, all LTCF residents and staff members in the facility were tested; three secondary cases (one in a staff member and two in residents) in persons who were close contacts of the bar attendee with COVID-19 were identified in the facility 5–9 days after the event. One resident with a secondary case was hospitalized on February 20, within 14 days of the positive test result, and was discharged the same day. None of the four persons in the LTCF with bar attendee or secondary COVID-19 had received a COVID-19 vaccination; all LTCF staff members and residents had been previously offered the vaccine.
By February 26, 12 household contacts in eight different households had received positive SARS-CoV-2 test results, including five school-aged children. Local health department staff members interviewed household contacts to assess exposures. Secondary household cases were linked to nine (31.0%) of 29 bar attendee cases. Eleven persons were symptomatic, and cases were confirmed by NAAT or antigen testing. No household contacts with COVID-19 were hospitalized.