7/14/2023 0 Comments Italy lockdownOne week after lockdown, on March 18, 5/93 provinces (5.4%) had an average R t <1, whereas on March 25 this figure increased to 49/96 provinces (51.0%). As of March 10, no province had a mean estimated value of R t <1 (n = 75 the number of symptomatic cases was insufficient for the estimate in 25 provinces). Results were consistent when analyzing estimates from the 100 selected provinces ( Figure 2). ![]() Green lines indicate average value of R t, weighted. Distribution of the mean net reproduction numbers for severe acute respiratory syndrome coronavirus 2 in 100 selected provinces in Italy. In the 3 weeks of March 26–April 15, R t remained stable in all regions, showing a further slight reduction at an average value of 0.76 (95% CI 0.67–0.85).įigure 2. The mean value of R t across the regions and autonomous provinces, weighted by the number of reported cases at the corresponding date, fell from an average of 2.03 (95% CI 1.94–2.13) on March 10 to 1.28 (95% CI 1.23–1.33) on March 18, to 0.88 (95% CI 0.84–0.91) on March 25, corresponding to an overall 62.6% reduction (range across regions 45.6%–85.0%). As of March 25, R t was <1 in most regions and autonomous provinces (12/21) and <1 in the successive 3 weeks for all regions except Molise and Piedmont ( Figure 1). One week into lockdown, on March 18, R t had decreased consistently, but no region or autonomous province was yet below the epidemic threshold ( Figure 1). On March 10, R t range was 1.79–3.36 across regions Basilicata and Molise had an insufficient number of symptomatic cases ( Figure 1). The R 0 range was 2.83–3.10 ( Figure 1) in the 8 regions for which the estimate was possible ( Appendix). Regions are sorted by decreasing number of. Basic (R 0) and net reproduction numbers for severe acute respiratory syndrome coronavirus 2 for all regions and autonomous provinces in Italy. These choices were suggested by the trend of the national R t ( Appendix).įigure 1. In addition, we considered the average value of R t over the successive 3 weeks (March 26–April 15). To evaluate the progressive decrease of transmission, we computed R t at 3 dates: the day before lockdown (March 10) and 1 and 2 weeks after lockdown (March 18 and 25). The selected provinces covered 99.1% of the population of Italy and, as of May 3, 2020, accounted for 153,558 symptomatic cases (97.9% of the total recorded in the surveillance database). ![]() Moreover, we considered 100 of the remaining 105 provinces for which the data were sufficiently complete. We considered all 19 regions in Italy plus the 2 autonomous provinces of Trento and Bolzano. To account for the geographic heterogeneity in contacts, healthcare organization, and timelines of interventions, R t was estimated separately for different provinces and regions. Estimates were obtained through a Bayesian approach applied to case-based surveillance data collected by regional health authorities ( Appendix). When R t decreases below the threshold of 1, the number of new infections begins to decline. ![]() These quantities represent the mean number of secondary infections generated by 1 primary infector in a fully susceptible population (R 0) and in the presence of control interventions and human behavioral adaptations (R t). We measured SARS-CoV-2 transmissibility in terms of the basic (R 0) and net (R t) reproduction numbers.
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