Cold-Season Epidemic Dynamics of COVID-19 in Two Major Metropolitan Areas in Greece: Hypotheses and Implications for Public Health Interventions

Spyros Sapounas; Angeliki Bistaraki; Edison Jahaj; Anastasia Kotanidou; Pagona Lagiou; Gkikas Magiorkinis

doi:10.3389/fmed.2022.861185

Cold-Season Epidemic Dynamics of COVID-19 in Two Major Metropolitan Areas in Greece: Hypotheses and Implications for Public Health Interventions

Front Med (Lausanne). 2022 May 30:9:861185. doi: 10.3389/fmed.2022.861185. eCollection 2022.

Authors

Spyros Sapounas¹, Angeliki Bistaraki², Edison Jahaj³, Anastasia Kotanidou³, Pagona Lagiou^{4

5}, Gkikas Magiorkinis⁴

Affiliations

¹ National Public Health Organisation, Athens, Greece.
² Department of Nursing, School of Health Sciences, Hellenic Mediterranean University, Crete, Greece.
³ First Department of Critical Care Medicine & Pulmonary Services - Evangelismos Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece.
⁴ Department of Hygiene, Epidemiology and Medical Statistics, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece.
⁵ Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States.

Abstract

Many respiratory viruses, including coronaviruses, follow seasonal transmission dynamics. Analyzing the social and environmental mechanics of the emergence of SARS-CoV-2 over the first cold season provides insight into designing targeted interventions. We analyzed all fully anonymized SARS-CoV-2 case data in two metropolitan areas, Attika and Thessaloniki, diagnosed between September 1st and December 31st, 2020. The emergence of the second wave in Greece occurred in October-November. SARS-CoV-2 diagnoses in Thessaloniki increased quasi-exponentially in mid-October, coinciding with the increase in the proportion of diagnoses in young people aged 18-39. The same pattern was observed in Attika with an almost 2-week delay, even though Attika had a higher prevalence of cases throughout summer until the second wave. Crucially, the nighttime temperature in Thessaloniki dropped below 18°C 3 weeks earlier than that in Attika. Epidemic growth was independently associated with the proportion of cases attributed to the 18-39 age group as well as with the drop in nighttime temperature below 18°C in both metropolitan areas but with a time difference. This pattern can be explained by a shift of nighttime entertainment activities from open-air to closed spaces, which occurs as nighttime temperature drops. Vaccination of young individuals can be crucial in decelerating the cold-season dynamics of SARS-CoV-2.

Keywords: COVID-19; SARS-CoV-2; epidemic; prevention; vaccines.