Acknowledgements
We are grateful for the essential work of a large number of public health experts, clinical microbiologists, practitioners and clinicians who have been involved in the investigations at national and regional level including all the professionals of the Canarian Health Service and the Balearic Islands Health Service. We acknowledge the work of ECDC data manager, particularly Zsolt Bartha, and country cooperation teams in rapidly establishing the online reporting system in TESSy by 26 January 2020. We thank also the efforts of Catalin Albu, Adrian Prodan, Skaidra Kurapkiene, Per Rolfhamre and Anca Dragnea. ECDC also thanks the Epidemic Intelligence team that provides vital and timely data on global cases of COVID-19. WHO thanks Ka Yeung (Calvin) Cheng, Silviu Ciobanu, Gudrun Freidl, Lauren MacDonald, and Miriam Sneiderman for assistance with data management.
Funding statement: No specific funding.
The authors alone are responsible for the views presented in this manuscript and they do not necessarily reflect the views, decisions or policies of the institutions with which the authors are affiliated.

Conflict of interest: None declared.
Authors’ contributions: EB and BC developed the surveillance system and reporting protocol. GS, JB, EB, CA, NB and BC initiated and developed the initial outline of the manuscript. GS performed the analysis. GS, BC, JB, NB, CA, EB wrote the first draft of the manuscript. JF, PJ, DP, JP, RP, SO contributed extensively to additional versions of the manuscript. MD, CC, VE, AG, AB, PS, MJSM, ANR, YVD, RoM, MBr, MBe, SBu, JS, LF, ALe, CS, AM, DLB, BC, SBS, SBe, SvdW, MV, BL, FR, EN, IC, ALa, MSC, FP, RiM, CM, MVR, NB, LS, SJ, KTW, MP were involved in national clinical, microbiological and public health investigations as well as data collection and reporting. All authors provided input to the outline, multiple versions of the manuscript and gave approval to the final draft.