Table 3.

Eight Characteristics of Pandemics.

The eight characteristics are related to the microbes themselves, or to the human–microbe interaction.^*

Feature	Comments
Novelty	Mostly unknown to the medical profession
Minimal population immunity	Frequent absence of specific IgG antibodies
Explosiveness	Determined mainly by size or density of population and factors related to type of transmission, for example vector population
Fast disease movement	Type and speed of human transmission
Wide geographic extension	Social interaction of populations, widespread common source
Infectiousness	Ability of microbes to produce disease (minimal infective dose)
Contagiousness	Proportion of completely asymptomatic cases, super-spreaders, and evident and pathognomonic disease markers
Severity	Need for hospitalization, artificial ventilation, or intensive rehydration; chronicity or death

^*Examples of interacting human factors include background immunity, means of transmission, and healthcare system quality.