A SARS-COV-2 (B.1.1.7) outbreak at a non-COVID inpatient ward at a hospital: lessons learned

Introduction: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineage B.1.1.7 has an increased transmissibility compared to predecessor lineages. Healthcare workers (HCWs) are at an increased risk of being exposed to SARS-CoV-2 but also of being a source of transmission. Objectives: To describe the lessons learned from a B.1.1.7 outbreak in a tertiary hospital. Methods: An Outbreak Management Team developed a mitigation strategy. 1) The importance of the prevailing infection control measures, including social distancing, capacity limits for rooms, universal masking in case of < 1.5 m distance and the early testing and domestic quarantine of HCW with symptoms was stressed. 2) An infection control practitioner visited the ward each working day during the outbreak period, to advise and observe practice. 3) Contacts were traced and divided into high-risk and low risk contacts in the workplace and in household/social contacts. 4) Voluntary nasopharyngeal swabs were taken twice a week, to detect asymptomatic cases. 5) Potential weak links of infection control measures were discussed with nurses. Results: Nine nurses and two informal caregivers tested RT-PCR positive for SARS-CoV-2 in December 2020. The index nurse tested positive following the earlier infection of a household contact. The outbreak was recognized a day later when the second nurse tested positive and was confirmed by Whole Genome Sequencing. Of the remaining nine cases which tested positive in the following 11 days, one case tested positive after a documented SARS-CoV-2 infection 83 days prior. We found a primary attack rate within the department of 18% and a secondary attack rate of 54% among contacts of positive cases. Short conversations in changing rooms without masks, short periods of lack of social distancing during breaks and the incorrect wearing of masks were mentioned as potential causes for transmission. Conclusion: Two keys point were taken from this outbreak with lineage B.1.1.7. First, it was controlled by adherence to guidelines in place, despite increased transmissibility of the variant. Second, reinfections with lineage B.1.1.7 can occur rapidly after primary infection. These lessons, reiterate the importance of adherence to prevailing infection prevention methods to prevent transmission among HCW.