[Infectious diseases: circumstances, chance... anything can be...]

Humanity has coexisted, lived together, and survived different severities in its history; one of them: the disease, which is suffered individually or in collective magnitudes manifested in epidemics and pandemics. In the 20th century and so far in this century various health damage events related to emerging and reemerging diseases have been identified, especially those of viral etiology. This editorial article takes a historical look at the main diseases faced in the last 100 years, focusing on human influenza and avian influenza and the recent COVID-19 pandemic.