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Estimates of the Severity of COVID-19
TAKE-HOME MESSAGE
- The authors' estimates of the case fatality ratio for COVID-19, although lower than some of the crude estimates so far, are substantially higher than the estimates for recent influenza pandemics. With the rapid geographical spread observed to date, COVID-19 represents a major global health threat in the coming weeks and months.
- The authors’ estimate of the proportion of infected individuals requiring hospitalization, when combined with likely infection attack rates, shows that even the most advanced healthcare systems are likely to be overwhelmed. These estimates are therefore crucial to enable countries around the world to best prepare as the global pandemic continues to unfold.
– Michael J. Allen, MD
abstract
This abstract is available on the publisher's site.
Access this abstract now Full Text Available for ClinicalKey SubscribersBACKGROUND
In the face of rapidly changing data, a range of case fatality ratio estimates for coronavirus disease 2019 (COVID-19) have been produced that differ substantially in magnitude. We aimed to provide robust estimates, accounting for censoring and ascertainment biases.
METHODS
We collected individual-case data for patients who died from COVID-19 in Hubei, mainland China (reported by national and provincial health commissions to Feb 8, 2020), and for cases outside of mainland China (from government or ministry of health websites and media reports for 37 countries, as well as Hong Kong and Macau, until Feb 25, 2020). These individual-case data were used to estimate the time between onset of symptoms and outcome (death or discharge from hospital). We next obtained age-stratified estimates of the case fatality ratio by relating the aggregate distribution of cases to the observed cumulative deaths in China, assuming a constant attack rate by age and adjusting for demography and age-based and location-based under-ascertainment. We also estimated the case fatality ratio from individual line-list data on 1334 cases identified outside of mainland China. Using data on the prevalence of PCR-confirmed cases in international residents repatriated from China, we obtained age-stratified estimates of the infection fatality ratio. Furthermore, data on age-stratified severity in a subset of 3665 cases from China were used to estimate the proportion of infected individuals who are likely to require hospitalisation.
FINDINGS
Using data on 24 deaths that occurred in mainland China and 165 recoveries outside of China, we estimated the mean duration from onset of symptoms to death to be 17·8 days (95% credible interval [CrI] 16·9-19·2) and to hospital discharge to be 24·7 days (22·9-28·1). In all laboratory confirmed and clinically diagnosed cases from mainland China (n=70 117), we estimated a crude case fatality ratio (adjusted for censoring) of 3·67% (95% CrI 3·56-3·80). However, after further adjusting for demography and under-ascertainment, we obtained a best estimate of the case fatality ratio in China of 1·38% (1·23-1·53), with substantially higher ratios in older age groups (0·32% [0·27-0·38] in those aged <60 years vs 6·4% [5·7-7·2] in those aged ≥60 years), up to 13·4% (11·2-15·9) in those aged 80 years or older. Estimates of case fatality ratio from international cases stratified by age were consistent with those from China (parametric estimate 1·4% [0·4-3·5] in those aged <60 years [n=360] and 4·5% [1·8-11·1] in those aged ≥60 years [n=151]). Our estimated overall infection fatality ratio for China was 0·66% (0·39-1·33), with an increasing profile with age. Similarly, estimates of the proportion of infected individuals likely to be hospitalised increased with age up to a maximum of 18·4% (11·0-7·6) in those aged 80 years or older.
INTERPRETATION
These early estimates give an indication of the fatality ratio across the spectrum of COVID-19 disease and show a strong age gradient in risk of death.
FUNDING
UK Medical Research Council.
Additional Info
Disclosure statements are available on the authors' profiles:
Estimates of the Severity of Coronavirus Disease 2019: A Model-Based Analysis
Lancet Infect Dis 2020 Mar 30;[EPub Ahead of Print], R Verity, LC Okell, I Dorigatti, P Winskill, C Whittaker, N Imai, G Cuomo-Dannenburg, H Thompson, PGT Walker, H Fu, A Dighe, JT Griffin, M Baguelin, S Bhatia, A Boonyasiri, A Cori, Z Cucunubá, R FitzJohn, K Gaythorpe, W Green, A Hamlet, W Hinsley, D Laydon, G Nedjati-Gilani, S Riley, S van Elsland, E Volz, H Wang, Y Wang, X Xi, CA Donnelly, AC Ghani, NM FergusonFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Estimates of COVID-19 Mortality
In essence, it all comes down to one question: if I get it, will I die? The advance of SARS-CoV-2 has been unrelenting, and worried clinicians and the members of general public are often left with a confusing array of mortality estimates for COVID-19. Creating a robust estimate is complicated by a wide variety of factors and the dizzying collection of denominators. We are fairly good at tallying the numbers of deaths due to COVID-19; we are terrible—at this point in time—at adequately describing the number of cases of COVID-19, or more broadly, the number of infections with SARS-CoV-2. Keep in mind, however, that we rarely do a much better job with our familiar respiratory pathogen, influenza.
The authors attempt to control for the surveillance biases that occur early in the tracking of a newly emerged pathogen, as focus is trained on clinically severe cases. To do so, they evaluated data from a wide variety of sources, including individual-level data within and outside of China, aggregated data in China, returning travelers from Wuhan, and cruise ship cases, to estimate contributions to the pyramid layers. Overall, the estimated case fatality rate in China is 1.38% (95% CI: 1.23—1.53); the infection fatality rate is estimated at 0.66% (95% CI: 0.39—1.33). The analyses also reconfirm the significant effect of age on case fatality rate, from 0.003% for children from 0—9 years to 13.4% for people aged ≥80 years.
At the end of the day, infection with SARS-CoV-2 is serious and associated with risk of death of 7 out of 1000. COVID-19 has a case fatality rate of about 14 per 1000. Whereas this risk is lower than some estimates, it is likely 10 to 100 times higher than that of seasonal influenza, and consequently, demands significant and continued medical and public health attention.
References