>>12354320Death rate has fallen because the lethal strain achieved a degree of Herd immunity through... deaths. However, this doesn't mean the disease is cured. At any time, in any human, a new lethal strain can be developed, and this will be causing local mortality epidemics until that strain as well stops from this dead herd immunity. The issue will be when a strain that is sufficiently infective turns out to be lethal in the long run or cause serious chronic issues, as viruses are well known to cause.
From this we can define new concepts in epidemiology.
Herd Immunity: The inability of a virus to infect an exposed population due to a broken chain of transmission.
Negligent immunity: The strategy that pretends to let the epidemiological natural course of the disease to run in a population in order to erradicate a disease without taking into account the possibility of mutations, development of reservoirs and the unreliability of antibody development in each individual.
Mortality epidemic: A period of increased mortality rate attributed to a disease higher than previous adjacent periods, related to the development of new strains.
