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A serosurvey of IgG antibodies against SARS-CoV-2 was conducted in Greece between May and August 2020. It was designed as a cross-sectional survey and was repeated at monthly intervals. The leftover sampling methodology was used and a geographically stratified sampling plan was applied. Of 20,110 serum samples collected, 89 (0.44%) were found to be positive for anti-SARS-CoV-2 antibodies, with higher seroprevalence (0.35%) observed in May 2020. The highest seroprevalence was primarily observed in the "30-49" year age group. Females presented higher seroprevalence compared to males in May 2020 (females: 0.58% VS males: 0.10%). This difference reversed during the study period and males presented a higher proportion in August 2020 (females: 0.12% VS males: 0.58%). Differences in the rate of seropositivity between urban areas and the rest of the country were also observed during the study period. The four-month infection fatality rate (IFR) was estimated to be 0.47%, while the respective case fatality rate (CFR) was at 1.89%. Our findings confirm low seroprevalence of COVID-19 in Greece during the study period. The young adults are presented as the most affected age group. The loss of the cumulative effect of seropositivity in a proportion of previous SARS-CoV-2 infections was indicated.

In this study, we assessed the effects of a 4 week basic military physical training programme for male recruits of the Hellenic Air Force on the number and distribution of circulating immune cells and adrenergic and adrenocortical hormonal responses. One group of recruits (exercised, n = 48) participated in moderate intermittent physical exercise, whereas a second group (non-exercised controls, n = 9) performed only light work in the barracks. Both groups participated in the same non-physical, classroom-type training and testing. Military training by the exercised group resulted in significant increases in CD4+ T-lymphocytes, renal cortisol excretion and the urinary noradrenaline/adrenaline ratio, together with reductions in neutrophils and the neutrophil/lymphocyte ratio. In the exercised group, the urinary noradrenaline/adrenaline ratio correlated positively with the training-induced changes in CD4+ T-lymphocytes and negatively with changes in the neutrophil/lymphocyte ratio. No significant relationship was found between training-induced increases in cortisol excretion and any of the peripheral blood cell alterations. Our results indicate that 4 weeks of military training consisting of intermittent moderate exercise resulted in a significant increase in CD4+ T-lymphocytes and reduction in neutrophils. These changes were probably driven by alterations in hormonal status, including the significant impact of sympathetic nervous system activation.