Detection of Influenza in Managed Quarantine in Australia and the Estimated Risk of Importation

Abstract

Background Influenza circulated at historically-low levels during 2020 and 2021 due to COVID-19 pandemic travel restrictions. In Australia, international arrivals to Australia were required to undertake 14 days hotel quarantine to limit new introduction of SARS-CoV-2 virus. Methods We used routine testing data for travellers arriving on repatriation flights to Darwin, Australia from 3 January to 11 October 2021 to identify importations of influenza virus into Australia and used this information to estimate the risk of a case exiting quarantine while still infectious. Influenza-positive samples were sequenced and cases were followed-up to identify transmission clusters. Data on the number of cases and total passengers was used to infer the risk of influenza cases existing quarantine while infectious. Results Despite very low circulation of influenza globally, 42 cases were identified among 15,026 returned travellers, of which 30 were A(H3N2), two were A(H1N1)pdm09 and 10 were B/Victoria. Virus sequencing data identified potential in-flight transmission, as well as independent infections prior to travel. Under the quarantine strategy in place at the time, the probability that these cases could initiate influenza outbreaks in Australia neared 0. However, this probability rose as quarantine requirements relaxed. Conclusions Detection of influenza virus infections in repatriated travellers provided a source of influenza viruses otherwise unavailable and enabled development of the A(H3N2) vaccine seed viruses included in the 2022 Southern Hemisphere influenza vaccine. Failing to test quarantined returned travellers for influenza, represents a missed opportunity for enhanced surveillance to better inform public health preparedness.

Is influenza B/Yamagata extinct and what public health implications could this have? An updated literature review and comprehensive assessment of global surveillance databases

“…Of the remaining 587 articles, 547 were discarded for not matching the inclusion criteria (of these, 62 were not further considered since no reported influenza cases were type B), 7 for being based on the WHO FluNet and/or GISAID database, 3 for being previous reports from the GIHSN, and 4 because of overlap with more recent and/or larger articles based on the same data sources. A total of 26 articles were included in the systematic review: their main characteristics are reported in Table 1 [ Soldevila 2022, Murillo-Zamora 2021, Korsun 2021, Panatto 2021, Pablo-Marcos 2020, Miron 2021, Hu 2021, Omer 2022, Olson 2022, Auvinen 2022, Kuzmanovska 2021, Wagatsuma 2022, Heinzinger 2021, Rios-Silva 2022, Suntronwong 2021, da Costa 2022, Melidou 2020, Huang 2022, O’Neill 2022, Kolosova 2022, Peck 2023, Chon 2023, Merced-Morales 2022, Melidou 2022, Sominina 2022, Song 2022 ]. Europe was the most represented area (12 articles, of which 2 reported findings from multiple countries in the WHO European Region), followed by Asia (n=6), North America (n=5), and Oceania and South America (n=1 each).…”

The re-emergence of influenza following the COVID-19 pandemic in Victoria, Australia, 2021 to 2022

“…In addition, a 14-day mandatory quarantine for returning Australian residents in supervised facilities (principally hotels) was introduced on 28 March 2020 [7]. Initiation of travel restrictions coincided with a dramatic reduction in influenza in Australia [8]. Only 33 of 60,031 specimens tested in Australia were positive for influenza between April and July 2020 [3], and between April 2020 and October 2021, confirmed cases were largely confined to quarantined travellers [8].…”

Antiviral therapies for influenza

“…There was also a global lack of influenza B/Yamagata identification in 2021 [8,9]. Nevertheless, sporadic cases of influenza infection have been reported [10], especially in tropical regions of Asia and West Africa [11,12 ▪ ]. With a gradual relaxation of NPI and the resumption of international travel in the year 2022 to 2023, seasonal influenza is expected to return [13].…”