An outbreak of 59 cases of coronavirus disease (COVID-19) originated with 13 cases linked by a 7 h, 17% occupancy flight into Ireland, summer 2020. The flight-associated attack rate was 9.8-17.8%. Spread to 46 non-flight cases occurred country-wide. Asymptomatic/pre-symptomatic transmission in-flight from a point source is implicated by 99% homology across the virus genome in five cases travelling from three different continents. Restriction of movement on arrival and robust contact tracing can limit propagation post-flight. Air travel has accelerated the global pandemic, contributing to the spread of coronavirus disease (COVID-19) throughout the world. We describe an outbreak that demonstrates in-flight transmission, providing further evidence to add to the small number of published studies in this area. This study depicts the nature of transmission on board, despite implementation of nonpharmaceutical interventions. We demonstrate widespread in-country transmission as a result of imported infection and give recommendations to reduce the risk of importation, and to curtail onwards spread. License, supplementary material and copyright This is an open-access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0) Licence. You may share and adapt the material, but must give appropriate credit to the source, provide a link to the licence and indicate if changes were made.

Objectives There is limited evidence on the risk of in-flight transmission of SARS-CoV-2. This study estimated the extent of in-flight SARS-CoV-2 transmission on international flights arriving into Ireland during December 2020. Study design Cross-sectional analysis. Methods National surveillance data identified all notified cases of COVID-19 who were infectious while travelling on international flights to Ireland during December 2020. Close contacts of cases were tested for SARS-CoV-2 and results were collated to estimate the pooled secondary attack rate across all flights. Laboratory and epidemiological data were obtained from the Health Service Executive Covid Care Tracker, a national database of COVID-19 cases in Ireland. Results 165 infectious cases of COVID-19 were identified on 134 incoming flights; 40.0% were symptomatic on board. There were 2,099 flight close contacts identified, of whom 40.9% had results of a SARS-CoV-2 PCR test within 14 days of arrival. The pooled secondary attack rate for these contacts was 7.0%, and was higher among those on flights of ≥5 hours duration (p=0.008). Over half (59.1%) of close contacts had no SARS-CoV-2 test result recorded; reasons included incorrect or absent contact details (26.5%), and no response when contacted (17.8%). Conclusions In this national study investigating transmission of SARS-CoV-2 from international flights arriving into Ireland, the pooled secondary attack rate was 7.0%. International travel is likely to have contributed to the third wave of SARS-CoV-2 infections in Ireland in early 2021. Application of non-pharmaceutical interventions remains central to mitigating the risk of in-flight transmission.

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Objectives Schools in the Republic of Ireland reopened to students and staff in late August 2020. We sought to determine the test positivity rate of close contacts of cases of coronavirus disease 2019 (COVID-19) in schools during the first half-term of the 2020/2021 academic year. Methods National-level data from the schools' testing pathway were interrogated to determine the positivity rate of close contacts of cases of COVID-19 in Irish primary, postprimary and special schools during the first half-term of 2020/2021 academic year. The positivity rates among adult and child close contacts were compared and the proportion of national cases of COVID-19 who were aged 4–18 years during the observation period was calculated to assess whether this proportion increased after schools reopened. Results Of all, 15,533 adult and child close contacts were tested for COVID-19 through the schools' testing pathway during the first half-term of the 2020/2021 academic year. Three hundred and ninety-nine close contacts tested positive, indicating a positivity rate of 2.6% (95% confidence interval: 2.3–2.8%). The positivity rates of child and adult close contacts were similarly low (2.6% vs 2.7%, P = 0.7). The proportion of all national cases of COVID-19 who were aged 4–18 years did not increase during the first half-term of the 2020/2021 school year. Conclusions The low positivity rate of close contacts of cases of COVID-19 in schools indicate that transmission of COVID-19 in Irish schools during the first half-term of the 2020/2021 academic year was low. These findings support policies to keep schools open during the pandemic.

Background Schools in Ireland closed in March 2020 as part of a national strategy to contain the spread of severe acute respiratory syndrome (SARS-CoV-2). The extent to which schools contribute to the overall propagation of SARS-CoV-2 was continuing to evolve internationally. Aims To examine regional data on SARS-CoV-2 transmission in primary, post-primary and special schools in Cork and Kerry, two counties in southwest Ireland, during the first 6 weeks of the 2020–2021 academic year and determine the rate of in-school transmission. Methods Data were obtained from the Computerised Infectious Disease Reporting (CIDR) system and supplemented with digital records from the regional Department of Public Health (Dept PH) and from the Health Service Executive (HSE) Covid Care Tracker application. The positivity rate among school close contacts was calculated to determine the rate of in-school SARS-CoV-2 transmission. Results The overall rate of in-school transmission of SARS-CoV-2 was low at 4.1%. Positivity rates among students and staff who were close contacts were similarly low (3.1% vs. 6.9%, p = 0.07). One secondary case of coronavirus disease 2019 (COVID-19) emerged, on average, for every 7.6 infectious days spent by an index case in school. Schools accounted for 2.2% of all notified cases of COVID-19 in the region during the observation period. Conclusions During the first 6 weeks of the academic year, the rate of in-school SARS-CoV-2 transmission in the region was low, and schools did not contribute substantially to the overall burden of COVID-19.