Spain’s Covid-19 outbreak: regional differences and asymptomatics

September 19, 2020

Daniel Howdon, Carl Heneghan, Jason Oke

see also: ‘As of September 3, case numbers appear to be flat.’

The most recent COVID-19 report issued by the Spanish government highlights two further points of interest, which demonstrate the importance of understanding the full intricacies available in the data, and which may have lessons for the analysis of data elsewhere.

(See here for the report)

First, this report breaks down the progression of the epidemic in each of the 17 provinces of Spain, some of which appear to have well past a local peak of cases when considered by date of symptoms.

This demonstrates further that national headline figures can mask that there is not one single national epidemic but one progressing differently, in different places, at different times

Second, recent figures appear to show a greater make-up of cases that are asymptomatic (light green line) relative to those that are symptomatic (dark green line) at the time of diagnosis.

This will have likely implications for the fatalities that would be expected to result from these cases. It is worth noting that these graphs are by date of diagnosis rather than the date of symptoms, with the use of the latter likely to introduce a bias that would tend to show more recent asymptomatic cases.

This highlights the vital importance of producing detailed data regarding the makeup of the type cases reported to aid understanding of the current status of the epidemic.

Daniel Howdon is a Senior Research Fellow in Health Economics, Leeds Institute of Health Sciences. Bio here 

Jason Oke is a Senior Statistician at the Nuffield Department of Primary Care Health Sciences and Module Coordinator for Statistical Computing with R and Stata (EBHC Med Stats), and Introduction to Statistics for Health Care Research (EBHC), as part of the Evidence-Based Health Care Programme.

Carl Heneghan is Professor of Evidence-Based Medicine, Director of the Centre for Evidence-Based Medicine and Director of Studies for the Evidence-Based Health Care Programme. (Full bio and disclosure statement here)

Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the authors and not necessarily those of the host institution, the NHS, the NIHR, or the Department of Health and Social Care. The views are not a substitute for professional medical advice.