Power spectra density and similarity analysis of COVID-19 mortality waves across countries

Johns Hopkins University CSSE documented waves of oscillatory COVID-19 mortality patterns worldwide during the COVID-19 pandemic. Here, we calculated the power spectrum density (PSD) of these COVID-19 mortality waves in 199 countries from January 22, 2020, to March 9, 2023. We identified two dominant peaks in the grand averaged PSD: one at a frequency of 1.15 waves per year (i.e., one wave every 10.4 months) and another at 2.7 waves per year (i.e., one wave every 4.4 months). Moreover, we performed a cosine similarity analysis of these PSD patterns among all the countries. The results showed a cosine similarity index distribution that was negatively skewed, with a skewness of -0.54 and a global median of cosine similarity index of 0.84, thus revealing a remarkable similarity in the dominant peaks of the COVID-19 mortality waves. These findings could be helpful if a future pandemic of a similar scale occurs so that effective confinement measures or other actions could be planned during these two identified periods, ensuring more assertive public health policies in advance. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Fundacion Marcos Moshinsky (EM), and Comite de Internacionalizacion de la Investigacion VIEP-BUAP (EM) Mexico. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: We employed the Johns Hopkins University CSSE COVID-19 database on GitHub.com to obtain the COVID-19 daily death counts for n=229 countries from January 22, 2020, to March 9, 2023. https://github.com/owid/covid-19-data/tree/master/public/data I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors