Environmental health in emergencies

Disease outbreaks

A mother at her sick child's bed in health care centre

A disease outbreak is the occurrence of disease cases in excess of normal expectancy. The number of cases varies according to the disease-causing agent, and the size and type of previous and existing exposure to the agent.

Disease outbreaks are usually caused by an infection, transmitted through person-to-person contact, animal-to-person contact, or from the environment or other media.

Outbreaks may also occur following exposure to chemicals or to radioactive materials. For example, Minamata disease is caused by exposure to mercury.

Occasionally the cause of an outbreak is unknown, even after thorough investigation.

Communicable disease outbreaks

Environmental factors influencing the spread of communicable diseases

Water, sanitation, food and air quality are vital elements in the transmission of communicable diseases and in the spread of diseases prone to cause epidemics.

Disease outbreaks caused by chemicals

Read more on diseases caused by chemicals

There are many examples of disease outbreaks that are due to exposure to chemicals or toxins.

Disease outbreaks of unknown etiology

Read more on disease outbreaks of unknown etiology

Occasionally, an outbreak is seen in a population for which the cause is unclear. Such an outbreak may be due to a new or modified pathogen, a natural toxin, or it may be due to an initially undetected release of a chemical agent or over-exposure to ionizing radiation.