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Different types of crises

(go to Outline)

"Humanitarian emergency", "man-made disaster", and "complex emergency" are all terms used to refer to a crisis which could be due to armed conflict, population displacement, or a combination of both. Imagine that you find yourself in the middle of any of the following scenarios:

  • A camp for refugees or internally displaced persons (IDPs) who have had to flee their communities of origin under the threat of violence and may have lost most of their possessions and livelihoods in the process. Think of IDP camps in Darfur, Sudan; Somalia; or northern Uganda.

Darfur, Sudan

  • A host community that receives an influx of refugees or IDPs, as occurred in Lebanon during the 2006 Israel-Hezbollah war or in Sri Lanka during the ongoing war.

Sri Lanka

  • A situation of chronic insecurity in which large populations are trapped between shifting frontlines or live under the constant threat of violence from militia groups or their own government - sometimes for months and years, as we see today in the eastern Democratic Republic of Congo, the Central African Republic, and Iraq.

Democratic Republic of the Congo

  • A sudden-onset natural disaster, such as flooding or earthquake, causing rapid environmental change and population displacement. Think of the Indian Ocean tsunami in 2004, the Pakistan earthquake in 2005, or the Sichuan earthquake in 2008.

Sri Lanka after tsunami

  • A severe food crisis due to natural and/or man-made conditions, such as the famine in the Somali region of Ethiopia in 2000 or the more recent example in Niger.


We know instinctively that health deteriorates in such conditions. This occurs as both

  • Direct health effects: people killed, wounded or traumatised by weaponry, intentional attacks, or the mechanical force of nature in disasters. In an earthquake, this may be crush injury from falling buildings. In a civil conflict, this may be gunshot injuries, wounds from shrapnel, or the psychiatric effects of witnessing or experiencing traumatic events. In a post-war situation, this may be the trauma resulting from accidental triggering of landmine or unexploded ordnance. Unlike conflict situations, direct health effects are of proportionately greater importance in natural disasters. (Click here for a more complete discussion of the role of indirect health effects, especially infectious diseases, after natural disasters.)
  • Indirect health effects: the increased risk of disease and death due to conditions brought about by the crisis. In a civil conflict, examples of indirect health effects include: 1) starvation because food sources have been destroyed or are unavailable; 2) occurrence of vaccine-preventable diseases because vaccination services are no longer offered because health facilities have been destroyed or health workers have fled; or 3) worsening of existing chronic diseases which go untreated because medications are unavailable. A review by the Human Security Project suggests that the majority of excess deaths in recent conflict-associated crises have in fact been due to indirect, not direct, causes. Increased risk of infectious disease mainly accounts for this indirect toll in conflict-affected populations in less developed countries. Only a few recent crises (e.g. the former Yugoslavia, Iraq and Lebanon) do not fit this general pattern. In these crises, most excess deaths were due to direct causes. Nonetheless, the incidence of several infectious diseases increased during these conflict.

A defining characteristic of health in crisis situations is that morbidity and mortality are elevated above background rates (see pages on Number of excess deaths). But how exactly do these deleterious effects happen?

In general, people are frequently exposed to agents which may cause disease, either infectious (bacteria, viruses, parasites, fungi, protozoa, helminths, or prions) or non-infectious (for example, carcinogenic substances, environmental pollution, missiles causing trauma, etc.). Many factors determine an individual's susceptibility to get disease upon exposure; for example, natural immunity from past infection, acquired immunity from immunization, age, nutritional status, genetic traits, behavioural factors, etc.

During any given time period, some susceptible persons are exposed to a disease-causing agent. Of those exposed, some become ill, and, of those who are ill, some die. We can break down this dynamic flow into four steps:

  • Susceptibility: the proportion of people who are potentially affected by the disease-causing agent.
  • The frequency and intensity of exposure to a disease-causing agent. For infectious diseases, this may be expressed as the transmission rate.
  • Progression to disease, once exposure or transmission has occurred.
  • Death as a result of the disease (also known as the case-fatality ratio [CFR], that is, the proportion of people who get the disease who die from that disease).

Crises can lead to: 1) increased susceptibility; 2) increased exposure to disease-causing agents, including enhanced transmission of infectious organisms; and 3) a higher proportion of people with the disease progressing to severe disease. These crisis-associated risk factors, in turn, produce more cases of disease (or higher morbidity). If the disease has the potential for resulting in death, higher morbidity often leads to more deaths (or higher mortality). The increase in mortality is further amplified by an increase in the case-fatality ratio also produced by crises.

The following table shows some examples of how crises can increase the morbidity and mortality from some specific infectious and non-infectious diseases.

Epidemiologic process Diarrhoea Neonatal tetanus Hypertension Post-traumatic stress disorder (PTSD)
The crises may increase the severity of undernutrition, which in turn depresses the immune system, making persons more susceptible to diarrhoeal diseases Because of war-related disruption to vaccination services, fewer pregnant women receive tetanus shots before giving birth, leaving more babies without immunity from the mother at the time of birth The causes of hypertension are mostly genetic or environmental; however, the environmental changes during crises may not make people more susceptible Almost everyone is susceptible to PTSD in a crisis, though some are more than others (e.g. combatants; people being persecuted; populations living in battle zones)
Exposure or transmission Displaced people may live in overcrowded camps with insufficient water and sanitation services: presence of and exposure to diarrhoeal pathogens in water or contamination of hands or food with faecal material will be more frequent Disrupted health services mean fewer pregnant women benefit from assisted deliveries: unsafe birth practices result in the baby's greater exposure to tetanus organisms Crisis-related stress might lead to more hypertension, as suggested by some evidence from post-earthquake studies Exposure to extraordinarily violent or other traumatic events is very frequent in most crises
Progression to disease Malnutrition greatly increases the chance that diarrhoeal infections, especially among children, will result in severe symptomatic disease Tetanus almost always results in disease, but symptoms may be more severe in low birth weight babies: low birth weight is associated with poor antenatal care, which often breaks down in crisis settings Forced displacement or inaccessibility of health services might leave many hypertensive patients without their routine medication, causing more to progress to symptomatic disease Traumatic exposures may progress to PTSD because of lack of psychological support and breakdown of normal life routines in the aftermath of the traumatic exposure
Death as a result of the disease (Case-fatality ratio or CFR) Diarrhoeal disease is almost 100% curable, but CFR will increase if health services have been disrupted by war, or displaced people do not receive sufficient relief Tetanus, like other neonatal infections, needs to be caught and treated early: inability to refer sick babies to hospitals, or lack of specialised treatment, will increase CFR about five-fold. Patients with life-threatening heart attacks or strokes resulting from uncontrolled hypertension may not receive treatment in time because inpatient facilities are unreachable or closed due to conflict Not likely, although in the absence of medical care and a supportive social environment, suicide could occur

The example of post-traumatic stress disorder reminds us that, while for most diseases the major goal of humanitarian interventions is to prevent death, there are also many conditions that, while rarely fatal, result in severe long-term disability and socio-economic distress for sufferers and their families. Mental illness and traumatic injuries are prime examples.

Another way to analyze the relationship between crises and disease is to classify risk factors as distal (occurring long before or at the beginning of the causal chain of the disease or death), intermediate (occurring somewhat later, closer to the disease onset or death), and proximate (occurring just before the onset of disease or death and most closely associated with the disease), as shown in this diagram:

This schematic shows examples of distal, intermediate, and proximate risk factors for excess morbidity and mortality in crises.

In general, humanitarian relief is directed toward the proximate factors listed above in the diagram because these factors are most closely associated with illness and death and because they are easier to target than intermediate or distal risk factors. Nonetheless, the important role of distal and intermediate risk factors must be appreciated and, if possible, addressed by policy and programme decisions.

Many of the risk factors discussed above interact in complex and poorly understood ways. For example, among the proximate risk factors, the interplay of infectious diseases and malnutrition is perhaps best understood. Even in stable contexts, malnutrition is estimated to be the underlying cause of about one in two deaths among children under five years of age. Malnourished people, especially children, are more susceptible to infection, experience more transmission, are more likely to progress to disease, and have a higher risk of death for many of the most common infectious diseases. In turn, many infectious diseases increase the severity of malnutrition, as shown below:

Known important interactions between malnutrition and various infectious diseases. The factor at the origin of each arrow exacerbates or produces the factors at the destination of the arrow.