3.1. Natural hazards

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Natural hazards (as defined earlier) such as earthquakes, hurricanes, and volcanic eruptions, among others, can have serious effects on health, but the impact varies as a function of various factors, including:

a) The severity of the hazard.

b) the vulnerability of the population.

c) The community’s state of preparedness and response capacity.


In the past, it was believed that sudden-onset disasters not only caused widespread mortality, but also produced massive social disorder, epidemics, and famines, leaving survivors totally at the mercy of international humanitarian relief. Systematic observation of the effects of natural disasters on human health has led to very different conclusions, both with respect to health effects themselves and as regards the most effective ways of providing humanitarian assistance.

 

Although all disasters are unique in that they affect areas with different degrees of vulnerability and with their own particular economic, health, and social conditions, they do have similarities. Identification of the common issues can lead to improved management of humanitarian health assistance and the use of resources. The following issues are worthy of consideration:
 

  • There is a relationship between the type of disaster and its health impact, particularly regarding injuries from the immediate impact. For example, earthquakes cause many injuries that require medical care, while floods and tsunamis cause relatively few.
     
  • Certain effects of disasters involve potential risks more than they entail inevitable threats to health. Displacements of populations and other changes in the environment, for instance, can increase the risk of disease transmission, but natural disasters are not commonly the cause of epidemics.
     
  • Real and potential health risks in the wake of disasters do not materialize all at the same time. Rather, they tend to appear at different times and to have varying degrees of importance within the affected areas. Thus, personal injuries occur usually at the time and place of the disaster event, requiring immediate medical care, while the risk of an increase in communicable diseases becomes evident more slowly, becoming most intense when there is overcrowding and a deterioration of sanitary conditions.
     
  • The need for food, clothes, shelter, and primary health care created by disasters is not usually absolute; even displaced people tend to have some of their vital needs met. Furthermore, the affected population tends to recover quickly from an initial state of stupor, and participates spontaneously in search and rescue efforts, transportation of the injured, as well as in other activities to provide relief to affected individuals.
     
  • Wars and civil conflicts create a unique set of health problems and operational obstacles. These situations are not covered in depth in this portal.


The following table summarizes and illustrates the short-term effects of disasters:

 

Effect

Earthquakes

High winds (without flooding)

Tidal waves and flash floods

Slow-onset floods
Landslides
Volcanoes and lahars

Deaths*

Many
Few
Many
Few
Many
Many*

Severe injuries requiring extensive treatment

Many
Moderate
Few
Few
Few
Few

Increased risk of communicable diseases**

Potential risk following all major disasters (probability rising with overcrowding and deteriorating sanitation)

Damage to health facilities

Severe (structure and equipment)
Severe
Severe but localized
Severe(equipment only)
Severe but localized
Severe (structure and equipment)

Damage to water systems

Severe
Light
Severe
Light
Severe but localized
Severe

Food shortage

Rare (may occur due to economic and logistic factors)
Common
Common
Rare
Rare

Major population movements

Rare (may occur in heavily damaged urban areas)
Common (generally limited)

Economic impact

Severe
Severe
Severe but localized
Moderate
Severe but localized
Severe but localized

 * The number of deaths bears a direct a relationship to the efficiency of the community’s warning system.
** Dependent on the aggressiveness of the epidemic and the speed of response.

 

Below is a list of some of the most frequently occurring natural hazards, with summary descriptions of their effects on health (the most frequent diseases and impact on health services) as well as references to material that provides more detailed information.


Some natural hazards 

3.1.1 Earthquakes

3.1.2 Tsunamis

3.1.3 Volcanic eruptions

3.1.4 Hurricanes and destructive winds 

3.1.5 Floods

3.1.6 Drought