## 4 Discussion
If we still allow transmission to continue upwards, we will have many hospitalized, many admitted to the intensive care units (ICU), and many deceased\", declared the director of the Centre for Coordination of Health Alerts and Emergencies of the Spanish Ministry of Health [26]. The 14 day predictions are used as nowcasting to know in real time the evolution of infections. For this, the hypothesis was assumed that an average of 14 days elapse between infection and registration as a case of COVID-19. Although this is very approximate, it is possible to make a rough estimate of the delay time between the day of infection and the date of inclusion and publication as a confirmed case by the health authorities. For COVID-19, it was estimated by [PERSON] et al. [27] that the median incubation period is 5.1 days (95% CI, 4.5 to 5.8 days) and that less than 2.5% of infected people will present symptoms within 2.2 days (CI, 1.8 to 2.9 days) of exposure, while the onset of symptoms will appear in 11.5 days (CI, 8.2 to 15.6 days) for 97.5% of infected people. There is also a variable number of days of delay between the onset of symptoms until the date of registration as a confirmed case of COVID-19 by the health authorities and its inclusion in the epidemic statistics. In Spain, this delay, according to information from RENAVE(National Epidemiological Surveillance Network) [28], includes a median of two days (IQRs 1-4) from the onset of symptoms to consultation and a median of one day (IQRs 1-2) from consultation to diagnosis. There is no information on the delay between diagnosis and inclusion and data released by the Ministry, but it can be assumed that this delay should be about 1-2 days. Therefore, it is not risky to estimate an average total delay of about two weeks from infection to inclusion in official statistics. Table 4 shows the information that would have been available applying the nowcast values obtained using the algorithm developed in this work. Figure 9: Seven day average estimation between 29 June and 2 September. On 28 June, the favorable nowcast indicated that the infections were controlled (the negative value makes no more sense than to indicate that in this scenario, there were no more new infections). However, the unfavorable scenario showed that more than three times more infections could be occurring than cases registered that day. Obviously, the nowcast shows a notable lack of definition about how the pandemic would evolve. However, two weeks later, the situation had changed, since both the favorable and unfavorable scenarios indicated that on 12 July, there were between 2.6 and 2.8 times more infections than the registered cases, and the 28 June unfavorable scenario was confirmed with more than 1000 new infections daily. These nowcasts clearly show the advisability of adopting restrictions and implementing NPIs, at least in the highest incidence geographic areas. On 26 July, the situation had notably worsened: the registered cases had multiplied by more than three, and there were between 2.3 and 2.4 times more infections than the registered cases. Many experts criticized the late reaction of central and regional authorities, the slowness of decision-making processes, and the low dependence on scientific advice [29]. On 6 September, the number of cases and the unfavorable nowcast indicated that pandemic spread had acquired a very high rate. However, between 19 September and 3 October, there were sudden changes in the immediate predictions, perhaps due to the confluence of negative factors (opening of schools) and positive factors (decreased mobility associated with holidays) together with the implementation of new NPIs. The irregularities shown by the nowcasts of 19 September and 3 October are a reflection of those that occur in the records of the cumulative number of cases that, at the time of writing this work, indicate an indefiniteness of trends, as can be observed in the epidemic curve of daily cases in Figure 10, with numerous irregularities since mid-September.