3.3. Effects of disasters
Disasters affect communities in multiple ways. They represent a public health hazard for various reasons (Table 2):
- They can cause an unexpected number of deaths and injured or sick people that exceed local response capacity and require external aid.
- They can destroy health infrastructure, affecting the immediate response and disrupting preventive activities, which may lead to long-term increases in morbidity and mortality.
- They can have adverse effects on the environment, increasing the risk of infectious diseases and environmental hazards. This can affect morbidity, premature death, and future quality of life.
- They can affect the psychological and social behaviour of the community.
- They can cause shortages of food, with severe nutritional consequences.
- They can cause large population movements, whether spontaneous or organised, to areas where health services may be unable to meet increased demand.
Table 2. Frequent effects of disasters by type
| Complex emergency |
| Immediate deaths |
Numerous |
| Severe lesions |
Numerous |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Moderate; can be severe if health centres are military targets |
| Damage to water supply |
Severe |
| Food shortage |
Severe |
| Significant population displacements |
Frequent |
| Earthquake |
| Immediate deaths |
Numerous |
| Severe lesions |
Numerous |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe |
| Damage to water supply |
Severe |
| Food shortage |
May result from economic and logistic factors |
| Significant population displacements |
Frequent; increased likelihood in severely damaged urban areas |
| Strong winds |
| Immediate deaths |
Few |
| Severe lesions |
Moderate |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe |
| Damage to water supply |
Slight |
| Food shortage |
May result from economic and logistic factors |
| Significant population displacements |
Not frequent |
| Floods |
| Immediate deaths |
Numerous |
| Severe lesions |
Few |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe but localised |
| Damage to water supply |
Severe |
| Food shortage |
Frequent |
| Significant population displacements |
Frequent |
| Gradual floods |
| Immediate deaths |
Few |
| Severe lesions |
Few |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe (equipment only) |
| Damage to water supply |
Slight |
| Food shortage |
Frequent |
| Significant population displacements |
Frequent |
| Mudslides |
| Immediate deaths |
Numerous |
| Severe lesions |
Few |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe but localised |
| Damage to water supply |
Severe but localised |
| Food shortage |
Not frequent |
| Significant population displacements |
Frequent |
| Volcanic eruptions |
| Immediate deaths |
Numerous |
| Severe lesions |
Few |
| Increased risk for transmissible diseases |
This risk applies to all significant disasters and increases with overcrowding and deterioration of sanitary conditions. |
| Damage to health centres |
Severe |
| Damage to water supply |
Severe |
| Food shortage |
Not frequent |
| Significant population displacements |
Frequent |
Adapted from Humanitarian Assistance in Disaster Situations. A Guide for Effective Aid. Pan-American Health Organization (PAHO). Washington D.C., 1999.