Some keys must be taken into account to interpret all these figures.
👉 Be careful when comparing the case figures with those of March. Detection today is better and there are many mild cases that were then ignored. Partly because of that, there will now be fewer hospitalized and fewer deaths for every known case.
👉 Death data is late. The normal rhythm of the disease causes cases to move earlier. For example, when there is a rebound, it will be appreciated first in the numbers of positives, then in hospitals and, finally, in deaths. Typically, deaths today are proportional to cases two or three weeks earlier.
👉 The hospitalized are a confirmation. A spike in cases can sometimes be due to better detection, so hospital figures are also useful to confirm that the spike is real. Another similar sign is the positivity numbers.
👉 How reliable is this data? The figures of the national and regional evolution come out of the report ministry journal. The positives come out of the SiViES system, which was launched in May, and they don’t seem to have long delays. Regarding income, the report offers two sources, that of SiViES and that reported by hospitals, but we take the second because the ministry has recognized that some communities are not updating the first promptly. Those same delays surely occur with deaths.
The situation and evolution by province
The map shows the still photo of the virus through two basic indicators of the epidemic: the incidence of cases and the rate at which they grow. The first tells us how much virus there is in a region, in daily cases per million inhabitants. The second informs us of the trend – are more cases detected today than yesterday? -, measured with the reproductive number R. When R is greater than one, the virus spreads.
The dates are a week or 10 days ago because they show the cases at the time they began to have symptoms, but they are cases that were known recently, perhaps yesterday or the day before yesterday. The data is updated every Friday.
The indicators, in detail
Reproductive number (R). It is an estimate of the number of people that each infected person infects. In the absence of containment measures, that figure is around 3 and the virus grows exponentially. To avoid this, the R must be less than 1. To calculate the reproductive number from the new daily cases we use the EpiEstim package of R. We assume a mean time between infections of 4 -7 days, with a standard deviation of 2.9 , similar to that of this work from London School of Hygiene & Tropical Medicine.
Cases per million. We take the daily data of new positive cases (almost always by PCR) from each province and express them per million inhabitants.
National data source. The data at the national level comes from the daily reports of the Center for the Coordination of Health Alerts and Emergencies (CCAES), dependent on the Ministry of Health. We use the reported totals — cases, admissions, and deaths — to calculate the weekly increase and divide it by seven to get a daily average. The reports give two figures for hospital admissions, the one from SiViES and the one reported by the hospitals, but we use the latter because it seems better up-to-date.
Source of series and map by provinces. The data comes from covid-19 situation panel maintained by the Carlos III Health Institute, from the declaration of cases through the SiViES computer platform managed by the National Epidemiology Center. They are data by date of symptoms: “From the beginning of the pandemic until May 10, the date of onset of symptoms is used or, failing that, the date of diagnosis minus six days. As of May 11, for symptomatic cases the date of onset of symptoms or, failing that, the date of diagnosis minus three days is used; in asymptomatic cases, the date of diagnosis is used ”.
Updating of the data. All information is normally updated on Thursday afternoons, which is when the covid-19 situation panel from the Carlos III Health Institute.
Information about the coronavirus
– Here you can follow the last hour on the evolution of the pandemic
– This is how the coronavirus curve evolves in Spain and in each autonomy
– Search engine: The new normal by municipalities
– Questions and answers about the coronavirus
– Guide to action against the disease
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