: Epidemic and outbreak of Disease What are the differences between an epidemic and an outbreak? Both words mean unexpected or unusual occurrence of the disease. Can someone explain the difference between them?

Vote Up Vote Down   0 Reactions

Login to give Reaction!

An outbreak is the sudden occurrence of a
disease in a community, which has never
experienced the disease before or when cases
of that disease occur in numbers greater than
expected in a defined area. The current Ebola
scenario in West Africa started as an
outbreak, which initially affected three
countries.
So what exactly is an epidemic? It is an
occurrence of a group of illnesses of similar
nature and derived from a common source, in
excess of what would be normally expected in
a community or region. A classic example of
an epidemic would be Severe Acute
Respiratory Syndrome (SARS). The epidemic
killed about 774 people out of 8,098 that were
infected. It started as an outbreak in Asia and
then spread to two dozen countries and took
the form of an epidemic. The same is true for
Ebola, which is now being termed an
epidemic .

Vote Up Vote Down   0 Reactions

Login to give Reaction!

As a practicing epidemiologist, I'm actually a little puzzled as to the down-votes for this. The difference between an outbreak and an epidemic is pretty subtle, and neither is all that terribly well defined.

The answer: There's not much of a difference.

The CDC agrees with me:

Occasionally, the amount of disease in a community rises above the
expected level. Epidemic refers to an increase, often sudden, in the
number of cases of a disease above what is normally expected in that
population in that area. Outbreak carries the same definition of
epidemic, but is often used for a more limited geographic area.

In practice, I'd argue that an outbreak is, as they mentioned, a somewhat smaller-scale phenomena. I'd talk about an outbreak of norovirus at a university, while I'd say a state, large city or country was having an epidemic.

I'd also say that, for very low levels of disease, it's possible to have an outbreak without an epidemic. For example, in a paper I wrote, I characterized the cases of disease in a population as "Low-level endemic spread, punctuated by periodic, short-lived outbreaks". These outbreaks were on the scale of less than a dozen people, so I'd really have a hard time calling it an epidemic, but again, this is referencing the idea that "outbreak" refers to a somewhat smaller geographical scale.