[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Epidemiology](https://durgical.com/en/epidemiology/) › [Surveillance and outbreaks](https://durgical.com/en/epidemiology/areas/outbreaks/) › Endemic, epidemic, outbreak and pandemic

# Endemic, epidemic, outbreak and pandemic

- Concept

An epidemic is defined not by how many cases there are, but by how many more than expected appear in that place and time.

Updated Nov 5, 2026

## Key points

- Endemic: the constant presence or usual prevalence of a disease in an area.
- Epidemic: a rise, often sudden, in cases above what is expected for that population, place and season.
- Outbreak: the same as an epidemic, used mostly for a limited area or group (a school, a neighbourhood).
- Pandemic: an epidemic spread over several countries or continents, affecting many people.
- Sporadic: infrequent, irregular cases; hyperendemic: high and persistent levels.
- A single case of a disease that is eliminated or never seen in the area (for example, polio in the Americas) is already handled as an outbreak.

## What it is

These terms compare the observed cases with the expected level of a disease in a population. Endemic means the usual, constant presence; epidemic, a rise above what is expected; outbreak, an epidemic in a limited area; pandemic, an epidemic spread across several countries or continents. Sporadic describes rare, irregular cases and hyperendemic, high and persistent levels.

## Worked example

- Data (made up): in one department, week 12 of the last 5 years had 36, 40, 44, 38 and 42 dengue cases.
- Expected level: (36 + 40 + 44 + 38 + 42) / 5 = 200 / 5 = 40 cases for week 12.
- An upper limit of the usual is set at 55 cases (the endemic channel computes it from past years).
- Week 12 this year: 90 cases; 90 / 40 = 2.25 times the expected and above the limit of 55.
- Reading: 40 weekly cases were endemic; 90 cases are an epidemic even though dengue is usual in the area.
- Contrast: a school with 0 to 1 hepatitis A case a year has 12 cases in 3 weeks: a local outbreak.
- If the same disease spreads to several continents with sustained transmission, it is called a pandemic.

## How the level of a disease is named

| Term | Compared with expected | Reach |
| --- | --- | --- |
| Sporadic | Rare, irregular cases | Any |
| Endemic | The usual level | A defined area |
| Hyperendemic | High and persistent | A defined area |
| Outbreak | More than expected | Limited area or group |
| Epidemic | More than expected | Region or country |
| Pandemic | More than expected | Several countries or continents |

## Markers

- Endemic
- Epidemic
- Outbreak
- Pandemic
- Endemic channel

## In practice

- In Colombia, the National Institute of Health and local health offices compare weekly cases with endemic channels to declare an alert.
- A doctor who notices more cases than usual should report them: surveillance finds outbreaks because someone compares with the expected.

## Common pitfalls

- Thinking endemic means many cases: it can be a low but constant level.
- Calling a severe disease a pandemic: the term is about geographic spread, not severity.

## Memory aid

Endemic is the background noise; an epidemic is a shout above the noise; a pandemic is a shout that crosses borders.

## Test yourself

Think of the answer, then tap the question to see it.

## What defines an epidemic?

A number of cases above what is expected for that population, place and season, not a fixed number of cases.

## How do an outbreak and an epidemic differ?

They mean the same, but outbreak is used mostly for a limited area or group.

## A disease has high, persistent levels in a region. What is this called?

Hyperendemic disease (hyperendemicity).

## Why is a single measles case in a country that eliminated it handled as an outbreak?

Because the expected number is zero: one case already exceeds the expected level and can start transmission.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/epidemiology/endemic-epidemic-outbreak-and-pandemic/)

## Connections

## Related 5

- [Epidemic curve](https://durgical.com/en/epidemiology/epidemic-curve/)
- [Outbreak investigation](https://durgical.com/en/epidemiology/outbreak-investigation/)
- [Public health surveillance](https://durgical.com/en/epidemiology/public-health-surveillance/)
- [SIVIGILA: public health surveillance in Colombia](https://durgical.com/en/epidemiology/sivigila-public-health-surveillance-in-colombia/)
- [Basic reproduction number (R0) and herd immunity](https://durgical.com/en/epidemiology/basic-reproduction-number-and-herd-immunity/)

## Related conditions 3

- [Dengue](https://durgical.com/en/conditions/dengue/)
- [Measles](https://durgical.com/en/conditions/measles/)
- [COVID-19](https://durgical.com/en/conditions/covid-19/)

[← All of epidemiology](https://durgical.com/en/epidemiology/)

Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.

Sources: [Principles of Epidemiology | Lesson 1 - Section 11](https://archive.cdc.gov/www_cdc_gov/csels/dsepd/ss1978/lesson1/section11.html) (Centers for Disease Control and Prevention, 2012).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/endemic-epidemic-outbreak-and-pandemic/