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close this bookNatural Disasters - Protecting the Public's Health (PAHO-OPS, 2000, 133 p.)
close this folderChapter 7. Epidemiologic Surveillance and Disease Control
View the documentRisk of Outbreaks Following Disasters
View the documentSetting Up a Disease Surveillance System
View the documentPresentation and Interpretation of Collected Data
View the documentLaboratory Services
View the documentVaccination and Vaccination Programs
View the documentTransmission of Zoonoses

Risk of Outbreaks Following Disasters

Natural disasters may increase the risk of preventable diseases due to adverse changes in the following areas:

1. Population density. Closer human contact in itself increases the potential spread of airborne diseases. This accounts in part for the reported increases in acute respiratory infections following disasters. In addition, available sanitation services are often inadequate to cope with sudden increases in populations.

2. Population displacement. The movement of disaster victims may lead to the introduction of communicable diseases to which either the migrant or indigenous populations are susceptible.

3. Disruption and contamination of water supply and sanitation services. Existing water supply and sewerage systems and power systems are particularly vulnerable, and may be damaged by natural disasters. In the aftermath of the 1985 earthquake in Mexico City, for example, millions of inhabitants remained without a piped water supply for as long as several weeks. Drinking water is prone to contamination caused by breaks in sewage lines and the presence of animal cadavers in water sources.

4. Disruption of public health programs. After a disaster, personnel and funds are usually diverted to relief. If public health programs (e.g., vector control programs or vaccination programs) are not maintained or restored as soon as possible, communicable disease transmission may increase in the unprotected population.

5. Ecological changes that favor breeding of vectors. Unusual periods of rain, with or without flooding, are likely to affect the vector population density. This may involve an increase in mosquito breeding sites or the introduction of rodents to flooded areas. This will be discussed in Chapter 8.

6. Displacement of domestic and wild animals. As with human populations, animal populations are often displaced as a result of natural disasters, carrying with them zoonoses that can be transmitted to humans as well as to other animals.

7. Provision of emergency food, water, and shelter in disaster situations. The basic needs of the population are often provided from new or different sources. It is important to ensure that these new methods are safe and that they themselves are not the source of infectious disease.

Outbreaks of gastroenteritis, which are the most frequently reported diseases in the post-disaster period, are closely related to the first three factors mentioned above. Increased incidence (or at least increased reporting) of acute respiratory infections is also common in displaced populations. Vector-borne diseases will not appear immediately but may take several months to reach epidemic levels. It should be noted that humanitarian workers are at risk following sudden-impact natural disasters as well as the disaster victims.

The principles of preventing and controlling communicable diseases after a disaster are to:

· Implement as soon as possible all public health measures to reduce the risk of disease transmission;

· Organize a reliable disease reporting system to identify outbreaks and to promptly initiate control measures;

· Investigate all reports of disease outbreaks rapidly. Early clarification of the situation may prevent unnecessary dispersion of scarce resources and disruption of normal programs.