  This work systematically conducts a data analysis based on the numbers of
both cumulative and daily confirmed COVID-19 cases and deaths in a time span
through April 2020 to June 2022 for over 200 countries around the world. Such
research feature aims to reveal the temporal and spatial evolution of the
country-level distribution observed in COVID-19 pandemic, and obtains some
interesting results as follows. (1) The distributions of the numbers for
cumulative confirmed cases and deaths obey power-law in early stages of
COVID-19 and stretched exponential function in subsequent course. (2) The
distributions of the numbers for daily confirmed cases and deaths obey
power-law in early and late stages of COVID-19 and stretched exponential
function in middle stages. The crossover region between power-law and stretched
exponential behaviour seems to depend on the evolution of "infection" event and
"death" event. Such observation implies a kind of important symmetry related to
the dynamics process of COVID-19 spreading. (3) The distributions of the
normalized numbers for each metric show a temporal scaling behaviour in 2-year
period, and are well described by stretched exponential function. The
observation of power-law and stretched exponential behaviour in such
country-level distributions suggests underlying intrinsic dynamics of a virus
spreading process in human interconnected society. And thus it is important for
understanding and mathematically modeling the COVID-19 pandemic.
