A pandemic is characterized by the global spread of a novel disease strain that
has the potential to cause serious illness and elevated mortality in the human population.
The ability of any pathogen to infect people and inflict illness or death is dependent
on that pathogen’s virulence and transmissibility. For example, certain diseases
such as influenza can cause serious illness or death, and are easily spread from
person to person. Other diseases, such as Ebola virus, that cause very high mortality
rates but are less readily transmissible.
However, not all people are equally at risk from pandemics. This is because pandemic
emergence is more likely under certain conditions. For example, geographic regions
where many people live that also have large populations of animals that serve as
“mixing vessels”—which, depending on the pathogen, can include pigs, domestic poultry,
or bats—are more likely to ignite pandemics. In addition, a person’s chance of developing
serious illness after contracting a disease is dependent on that person’s age, sex,
and general health. Access to supportive medical care, antivirals, antibiotics,
and vaccines also plays an important role. Travel restrictions may help by slowing
the spread of a pandemic, allowing the dissemination of medical supplies and vaccines
before the first wave of illness arrives. In fact, if mitigation measures are promptly
enacted, many deaths may be prevented.