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Complex emergency/population movement

Complex emergency/population movement

Last update: 2022-11-14

Key facts

A complex emergency is a crisis where there is a breakdown of authority and response. This often results from conflict or instability and may be exacerbated by other threats, such as natural hazards or economic instability. Complex emergencies often lead to significant displacement and population movement. Population movement is intensified by climate change. The population is often affected by malnutrition, disease epidemics and poor overall health.

Main health impacts

Health concern

Risk factors


Mental health consequences

  • Mental health impacts including (but not limited to) severe anxiety, post-traumatic stress disorder (PTSD) and depression may occur as a result of experiencing the trauma of displacement and/or trauma caused by the event(s) that caused the displacement (for example, homelessness; losing loved ones; loss of livelihood; etc.).

  • Experiencing multiple traumatic events can lead to compound or complex trauma.


Malnutrition/micronutrient deficiency

  • Insufficient nutrient intake leads to increased vulnerability to infection, morbidity and mortality.

  • Vulnerable groups including children under five years of age, pregnant and lactating women, and people with chronic illness such as HIV and TB are especially at risk.

  • Lack of and/or delay in treatment of illness contributes to deteriorating nutritional status and makes malnourished people more vulnerable.

Diarrhoeal diseases

  • Limited access to water supplies and sanitation services lead to diarrhoeal diseases. During population movements, increased vulnerability can lead to large scale outbreaks of cholera and other infectious diseases.

  • Difficulty maintaining proper sanitation and hygiene practices can lead to problems such as diarrhoeal diseases.


Vector-borne diseases  

  • Lack of suitable shelter and lack of access to bed nets or other preventive measures increase exposure to and risk of vector- borne diseases


Respiratory illnesses, skin infections and vaccine- preventable diseases

  • Significant population displacement and overcrowded, communal emergency shelters coupled with difficulty maintaining proper sanitation and hygiene practices can lead to problems such as respiratory illnesses, skin diseases and some vaccine-preventable diseases.

  • High insecurity in complex emergencies can lead to the disruption of routine health services such as vaccination programmes, therefore increasing the risk of transmission of vaccine-preventable diseases (for example, measles).


Overall adverse health outcomes

  • Conflict and violence can lead to damage to health facilities and disruption to provision of health care services.

  • During population movements some groups may be unable to access existing services due to a range of obstacles (for example, inability to use services in other countries, high costs, persecution by authorities). Limited access affects many outcomes from  maternal and child health to noncommunicable diseases (NCDs).

  • Security concerns can hinder the availability of health care personnel, or can disturb their mental health, affecting the overall quality of care for community members.