Menni, C

Ourselin, S

Spector, TD

Steves, CJ

Sudre, CH

English

UCL Discovery

  Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website.  Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.  CorrespondenceSubmissions should be made via our electronic submission system at http://ees.elsevier.com/thelancet/www.thelancet.com   Vol 395   June 20, 2020 e107Quantifying additional COVID-19 symptoms will save livesPublic health authorities across the world have been trying to contain the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via public awareness and contact tracing—ie, by identifying and isolating individuals at high risk of being positive.1 In many countries, regular mass swab testing is still inadequate. To reduce the number of infectious people in the community, it is therefore crucial to use the symptom combinations that can identify them.Using self-reported symptoms data from 18 401 users of the COVID Symptom Study app, who under-went an official SARS-CoV-2 test (7104 testing positive, 11 297 testing negative), we previously reported that loss of smell and taste is a potential predictor of COVID-19 in addition to the most established symptoms of a high temperature and a new continuous cough.2 The prevalence of loss of smell and taste was three-fold higher in individuals testing positive (65∙03%) than in those testing negative (21∙71%),2 suggesting that people with loss of smell and taste should self-isolate. In April, 2020, WHO, along with many EU countries, the USA, and Australia added loss of smell and taste as one of the key COVID-19 symptoms, whereas the UK Government added it to its symptom list on May 18, 2020. The reason quoted for the reticence was reportedly that anosmia by itself (without cough or fever) is responsible for less than 2% extra cases.3 Our data suggest this not to be the case.As of May 19, 2020, of the more than 3∙2 million UK users of the COVID Symptom Study app,4 76 260 people have now been tested for SARS-CoV-2 and reported symptoms. 71∙5% of the 13 863 individuals testing positive indicated fever or cough, suggesting that only isolating and screening those reporting fever or cough could have missed almost 30% of positive cases. Consistent with our previous results,2 loss of smell and taste was reported overall by 64∙5% of those testing positive; and by 15∙9% of those not suffering from either fever or cough. These findings are depicted in a Venn diagram in the appendix. New onset loss of smell and taste is a symptom, which is particularly relevant for the young and working population who are likely to be ambulant and able to spread the disease. This 15∙9% without classic symptoms could be very relevant to reducing spread.We also quantified the sensitivity, specificity, positive predicted value, and negative predicted value of fever, cough, fever or cough, and loss of smell in 76 260 users of the COVID Symptom Study app who underwent the SARS-CoV-2 test (13 863 testing positive; 62 397 testing negative; appendix). We found the predictive ability of loss of smell and taste to be higher than fever or persistent cough, which is in line with our previous finding that loss of smell and taste was the strongest predictor of having the virus.2 Moreover, we found that the median duration of anosmia symptoms was 5 days, whereas the median duration of fever was only 2 days.As countries slowly emerge from lockdown measures, it is imperative to correctly contact-trace infected individuals. We believe that having added loss of smell and taste to the list of COVID-19 symptoms is of great value as it will help trace almost 16% of cases that otherwise would have been missed. Loss of smell and taste, together with fever or cough, should now enable us to identify 87∙5% of symptomatic COVID-19 cases, although this is likely to be less in the early phases of the infection.Our results also provide theoretical support for adding more symptoms to Public Health England’s list of symptoms, as WHO and other countries have done. The danger is that, unlike loss of smell and taste, many symptoms might be non-specific and might need algorithms, as the ones used in the COVID-19 Symptom Study app, to increase predictive power.Like all observational studies, our findings have limitations and rely on self-report of symptoms, as do most strategies outside of mass population testing. Direct self-testing for new onset loss of smell and taste could improve symptoms capture and should open doors to confirmatory testing. However, loss of smell and taste could be a less discriminating symptom in older people and by those who are less able to report symptoms, such as people in care homes.We believe that loss of smell and taste is a common COVID-19 symptom and that infections could be reduced and lives saved now that this non-flu-like symptom is recognised. Our data suggest that low-cost so-called smell the difference screening tests, instituted in workplaces and entrances in some settings worldwide, might capture a larger number of positive cases than temperature sensors do.Ultimately, all individuals have an interest in isolating if they have any symptoms of the disease, and less overtly symptomatic people might have unwittingly been silent spreaders.CM declares funding through a National Institute for Health Research Clinical Doctoral Research Fellowship. CHS declares a grant from the Alzheimer’s Society. SO declares grants from Wellcome and from UK Research and Innovation. TDS is a consultant to Zoe Global. CJS declares no competing interests. Cristina Menni, Carole H Sudre, Claire J Steves, Sebastien Ourselin, *Tim D Spectortim.spector@kcl.ac.ukDepartment of Twin Research and Genetic Epidemiology (CM, CJS, TDS) and School of Biomedical Engineering and Imaging Sciences (CHS, SO), King’s College London, SE1 7EH London, UK1 Ferretti L, Wymant C, Kendall M, et al. Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing. Science 2020; 368: eabb6936.2 Menni C, Valdes AM, Freidin MB, et al. Real-time tracking of self-reported symptoms to predict potential COVID-19. Nat Med 2020; published online May 11. DOI:10.1038/s41591-020-0916-2.Published Online June 4, 2020 https://doi.org/10.1016/ S0140-6736(20)31281-2For the COVID Symptom Study app see covid.joinzoe.comSee Online for appendixCorrespondencee108 www.thelancet.com   Vol 395   June 20, 20203 Smyth C. ‘Smell loss has little effect on coronavirus case tallies’. May 19, 2020. https://www.thetimes.co.uk/article/smell-loss-has-little-effect-on-coronavirus-case-tallies-230nm82vl (accessed June 1, 2020).4 Drew DA, Nguyen LH, Steves CJ, et al. Rapid implementation of mobile technology for real-time epidemiology of COVID-19. Science 2020; published online May 5. DOI:10.1126/science.abc0473.

Quantifying additional COVID-19 symptoms will save lives

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Quantifying additional COVID-19 symptoms will save lives

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