key: cord-0903099-easfx7by
authors: Eyre, Toby A.; Peters, Louis; Andersson, Monique I.; Peniket, Andrew; Eyre, David W.
title: Reduction in incidence of non‐COVID‐19 respiratory virus infection amongst haematology inpatients following UK social distancing measures
date: 2021-06-07
journal: Br J Haematol
DOI: 10.1111/bjh.17651
sha: 1c45ee747117ce08f828fe8c1714d27da103b8ef
doc_id: 903099
cord_uid: easfx7by

Since the SARS‐CoV‐2 pandemic began, countries across the globe have seen repeated periods of government‐enforced social distancing to restrict transmission in response to rises in COVID‐19 incidence(1). Social distancing in the UK was first introduced in March 2020, and for 6 of the following 12 months the population was under strict national restrictions. This led to substantially reduced contact between different households(2), with mass gatherings prohibited.

Since the SARS-CoV-2 pandemic began, countries across the globe have seen repeated periods of government-enforced social distancing to restrict transmission in response to rises in COVID-19 incidence 1 . Social distancing in the UK was first introduced in March 2020, and for 6 of the following 12 months the population was under strict national restrictions. This led to substantially reduced contact between different households 2 , with mass gatherings prohibited.

Prior to this pandemic, respiratory viral infections were a common cause of morbidity amongst haematology patients 3 , including those immunosuppressed or post haematopoietic stem-cell transplantation (HSCT), with reported incidences of 3-30% per year 4, 5 . Respiratory Syncytial Virus (RSV) is the virus most likely to progress from upper respiratory tract infection to pneumonia in patients who have undergone HSCT [6] [7] [8] , and the British Society of Haematology recommends ribavirin and intravenous immunoglobulin in this group 9 . Influenza, parainfluenza, and adenovirus can all cause severe disease in the immunocompromised, and SARS-CoV-2 has been shown to cause severe disease and excess mortality in those who have undergone HSCT and some haematological malignancies 10-11 .

Regional surveillance networks have noted a significant reduction in influenza transmission in both southern 12 and northern hemispheres 13 (https://www.cdc.gov/flu/weekly/index.html) during their respective winter seasons in 2020-21. This has been attributed to non-pharmacological interventions and social distancing introduced to reduce SARS-CoV-2 transmission.

Here, we describe the impact of UK social distancing measures on the incidence of non-SARS-CoV-2 respiratory viral infection in a cohort of haematology patients. This article is protected by copyright. All rights reserved 14 , and has been updated to include SARS-CoV-2 detection.

All PCR results performed during haematology inpatient admissions (including encounters to the triage unit) were obtained from the Infections in Oxfordshire Research Database which has generic Research Ethics Committee, Health Research Authority and Confidentiality Advisory Group approvals (19/SC/0403, 19/CAG/0144). Data were also obtained on baseline characteristics including gender, age, ethnicity, haemato-oncological or benign haematology specialist care, and comorbidity indices (Charlson comorbidity index (CCI)).

We used piece-wise linear regression to model changes in admissions over time, and Poisson regression to model changes over time in incidence of testing per 100 admissions for respiratory viruses, allowing for a step change in incidence from March to April 2020, i.e. around the introduction of the first UK national lockdown on 16-March-2020, and a linear trend before and after this. We do not adjust for seasonality and so trends presented represent averages across seasonal peaks and troughs.

Between 01-January-2016 and 28-February-2021, across all haematological specialities at OUH, there were 22,536 inpatient encounters. Median age of patients was 59 (interquartile range, IQR, 18-71), 13 ,534 (60%) were male, 14,940/16,502 (91%) with recorded ethnicity were white and 21,817 (97%) were managed by a haemato-oncologist. Across this period, 3,380 BioFire PCR tests were performed in 2,719 haematology inpatients. Tested patients were older than untested patients, median (IQR) age 61 (49-70) vs. 58 (16-71) years (p<0.001) and had more comorbidities, CCI median (IQR) 8 (0-8) vs 0 (0-0) (p<0.001; Table S1 ). There was no evidence of a difference by sex or ethnicity. 

Our results show a clear, rapid decline in the incidence of pathogenic non-COVID-19 respiratory viruses in our cohort of haematology patients since the introduction of UK social distancing and other infection control measures. This mirrors a decline in detection rates of other respiratory viruses, including influenza, in the general population [12] [13] . RSV, influenza and adenovirus can be particularly pathogenic in the immunosuppressed, including those who have undergone HSCT or other T-cell depleting therapies, who form a significant proportion of our cohort. Although we have not directly studied mortality overall or in particular patient groups, based on historical data 6-8 it can reasonably be inferred that the reduction in incidence seen may have led to a concurrent reduction in viral-related mortality.

It is predicted that there may be a rebound in RSV incidence once social distancing measures are relaxed 15 , due to increased RSV susceptibility following reduced transmission during COVID-19-related This article is protected by copyright. All rights reserved restrictions. If this occurs, ongoing risk mitigation policies regarding personal social distancing and face mask use by subsets of haematology patients could be considered. However, immunosuppressed patients and their clinicians will need to weigh infection-related risks against the impact of social restrictions on patients' overall well-being, particularly given the restrictions already faced during the pandemic. We advocate for the ongoing surveillance of these pathogenic respiratory viral infections in the general population, to allow informed discussions with our patients, and counselling of the risks of complications of these infections considering current prevalence. This article is protected by copyright. All rights reserved 

Monthly respiratory virus detection rates (panel C).

The black line indicates observed values and the blue dotted line the modelled incidence, with the ribbon indicating the 95% confidence interval. The start of UK national social distancing restrictions is shown as a dashed red vertical line.

Quarterly incidence of respiratory virus infection in haematology inpatients.

For each virus the dashed line indicates the modelled incidence, and the ribbon the 95% confidence interval, allowing for a linear trend before and after the onset of UK national social distancing restrictions, and a step change at this point (shown with a vertical dashed black line).

Effect of the social distancing measures on the spread of COVID-19 in 10

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TAE recognizes support from the Oxford NIHR Biomedical Research Centre. DWE is a Robertson Foundation Fellow and an NIHR Oxford BRC Senior Fellow.This work uses data provided by patients and collected by the UK's National Health Service as part of their care and support. We thank all the people of Oxfordshire who contribute to the Infections in Oxfordshire