Which one of the following statements is FALSE regarding emerging infectious diseases:
a. Newly emerged infectious agents can survive in human populations without adapting to direct or indirect person-to-person transmission
b. Emergence of infectious disease can be attributed to new strains of previously know infectious agents
c. An infectious disease that has been recognised in humans for the first time is considered to be a newly emerging infectious disease
d. An infectious disease that reappears in a resistant form is considered to be a re-emerging infectious disease