Epidemiological characteristics of COVID-19 cases and estimates of the reproductive numbers 1 month into the epidemic, Italy, 28 January to 31 March 2020

  1. Flavia Riccardo
  2. Marco Ajelli
  3. Xanthi D Andrianou
  4. Antonino Bella
  5. Martina Del Manso
  6. Massimo Fabiani
  7. Stefania Bellino
  8. Stefano Boros
  9. Alberto Mateo Urdiales
  10. Valentina Marziano
  11. Maria Cristina Rota
  12. Antonietta Filia
  13. Fortunato D'Ancona
  14. Andrea Siddu
  15. Ornella Punzo
  16. Filippo Trentini
  17. Giorgio Guzzetta
  18. Piero Poletti
  19. Paola Stefanelli
  20. Maria Rita Castrucci
  21. Alessandra Ciervo
  22. Corrado Di Benedetto
  23. Marco Tallon
  24. Andrea Piccioli
  25. Silvio Brusaferro
  26. Giovanni Rezza
  27. Stefano Merler
  28. Patrizio Pezzotti
  29. the COVID-19 working group

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Abstract

On 20 February 2020, a locally acquired coronavirus disease (COVID-19) case was detected in Lombardy, Italy. This was the first signal of ongoing transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the country. The number of cases in Italy increased rapidly and the country became the first in Europe to experience a SARS-CoV-2 outbreak.

Aim

Our aim was to describe the epidemiology and transmission dynamics of the first COVID-19 cases in Italy amid ongoing control measures.

Methods

We analysed all RT-PCR-confirmed COVID-19 cases reported to the national integrated surveillance system until 31 March 2020. We provide a descriptive epidemiological summary and estimate the basic and net reproductive numbers by region.

Results

Of the 98,716 cases of COVID-19 analysed, 9,512 were healthcare workers. Of the 10,943 reported COVID-19-associated deaths (crude case fatality ratio: 11.1%) 49.5% occurred in cases older than 80 years. Male sex and age were independent risk factors for COVID-19 death. Estimates of R 0 varied between 2.50 (95% confidence interval (CI): 2.18–2.83) in Tuscany and 3.00 (95% CI: 2.68–3.33) in Lazio. The net reproduction number R t in northern regions started decreasing immediately after the first detection.

Conclusion

The COVID-19 outbreak in Italy showed a clustering onset similar to the one in Wuhan, China. R 0 at 2.96 in Lombardy combined with delayed detection explains the high case load and rapid geographical spread. Overall, R t in Italian regions showed early signs of decrease, with large diversity in incidence, supporting the importance of combined non-pharmacological control measures.

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  1. Version published to 10.2807/1560-7917.es.2020.25.49.2000790
  2. ScreenIT

    SciScore for 10.1101/2020.04.08.20056861: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    The analyses were performed using STATA (version 16) and R (version 3.6.3).
    STATA
    suggested: (Stata, RRID:SCR_012763)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The data collected from the Italian integrated COVID-19 surveillance system during the initial phase of the emergency presents a number of limitations mainly due to completeness challenges. For this reason, some stratifications and analysis were not shown. The lack of completeness on the presence and type of comorbidities, did not allow us to include this in the multivariable analysis of deaths in order to assess, and/or adjust for, this factor. Data on hospitalisation and ICU admissions as well as CFRs are not adjusted for the expected time for disease evolution and might therefore be under-estimated in the more recent period. Finally, the estimation of R0, Rt and the doubling time were performed in regions selected on the basis of the robustness of data considering epidemiologically diverse settings. Even in the presence of the mentioned limitations, our analysis suggests that the SARS-CoV-2 transmission potential in Italy is decreasing, albeit with large diversities across the country. Further, we observe that as of March 8 2020, the Rt it is still above the epidemic threshold. The progressively harsh physical distancing measures enacted since then may have enhanced the decreasing trend in transmissibility as happened in China [19,20]. The surveillance system will be key to monitor the effect of the implemented policies and guide the public health response as Italy will enter the second phase of its outbreak.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  3. Version published to 10.1101/2020.04.08.20056861v1 on medRxiv