*3.1. Epidemiological Investigation and Case Identification*

The LMPHU was notified of farmworkers who were symptomatic and presented to the pathology centre for SARS-CoV-2 viral PCR testing, which subsequently identified nine cases. Through contact tracing, further PCR testing, and rapid antigen testing, a cumulative total of 68 cases of the 74 farmworkers were identified, including 9 (13.8%) PCR-confirmed and 59 (86.8%) probable (Table 1). There were 42 staff contacts of which 3 later tested positive using a RAT and were able to isolate from their homes.


**Table 1.** Characteristics of COVID-19 cases in the outbreak (*n* = 68).

Initially, three confirmed cases were notified to the LMPHU on 8 January 2022 with their samples collected on 7 January 2022. This result turnaround was considerably quick considering the national overload all pathology services were experiencing due to the peaking of the Omicron variant of concern (VoC) in Australia. All cases in this cohort were cleared by 19 January 2022 (Figure 1). Figure 1 shows this as a point source outbreak with the epi curve flattening after 9 January 2022 and the last three probable cases diagnosed on 12 January 2022. The SARS-CoV-2 virus VoC agent for this outbreak was not determined. All cases that were initially symptomatic on testing or during the infection period were assessed as asymptomatic at least 24 h before clearance date and released from isolation. COVID-19-negative contacts were tested on 9, 12, and 14 January 2022 and continued to

longer infectious.

quarantine until 19 January 2022 when the last positive cases were considered to be no

**Figure 1.** Epidemic curve of confirmed and probable cases. Nine cases were initially identified by PCR on 7 January 2022; then a further 56 showed positive RAT tests on 8 and 9 January, and the last 3 were identified on 12 January 2022.

During the outbreak period, there were no deaths or requirements for hospitalisations among all workers; however, 10 (14.7%) cases had had minor COVID-19-related symptoms. Due to the few cases with minor symptoms, risk factors associated with the severity of infections could not be analysed. This cohort was mostly composed of male workers [57 (83.8%)]. The age group was mostly 30–39 years old [35 (51.5%)] followed by the 18–29 years old age group [24 (35.3%)]. All workers were younger than 50 years old (Table 1). Six workers that remained COVID-19-negative throughout the outbreak were all men with a median age of 28 years, whereas the case cohort had a median age of 32 years.
