Ken ITO
The University of Tokyo

Submitted 23 Apr 2020, Revised version accepted 4 May 2020

Global lethality of COVID-19, calculated as the ratio of total infected cases and total deaths,
increases from 4.69% in mid-March to 9.07% in mid-April, almost two times as large within
one month.
Usually in epidemiology, lethality is regarded as pathogen-specific constant value and in most
case this holds generally. However, COVID-19 is new corona virus and antibody therapy is
not yet established (Apr. 2020). At least one more year is expected to establish vaccine, and
to spread it globally. In such condition, clinical lethality has much relation to local medical
care in quality and quantity. Lethality could be interpreted as an indicator of regional
medical collapse and medical reestablishment. In advanced countries, medical collapse is
discussed in relation to the number of surplus hospital beds or respirators. However, in regard
to further spread of pandemic to developing countries and post-conflict areas, we should
define different phenomenological parameter to evaluate the degree of regional medical
collapse quantitatively.
The author defined “lethal velocity” from daily difference ratio of cases and that of deaths.
Using this lethal velocity, we analyze pandemic in different countries and regions. Further
correlation function analysis between pandemic and social, economic and medical disparity
are in preparation.