Epidemiological control measures in
communities affected by floods
Dr. Vicente García Gómez Epidemiology Specialist, Master of Public Health (MPH) Ministry of Public Health, Cuba, Advisor to CLAMED

INTRODUCTION

Floods constitute the most common type of natural hazards worldwide, given that they represent approximately 40% of these phenomena. Information compiled and published by the Red Cross International between 1900 and 1976 -regarding the damage caused by the main natural disasters that took place throughout the world during this period, shows that floods cause more victims than the rest of these disasters, and the number of deaths is only exceeded by those caused by earthquakes (Table 1).

Table 1
Natural Disasters between 1900 and 1976

Source: Red Cross International

According to Stop Disasters magazine, during the last 25 years the number of deaths caused by floods represent 8,6% of the total, as well as 80% of all individuals injured as a result of a natural disaster (Graphic 1).

Graphic 1
Information on disasters occurred in a 25-year period
Total deaths and injured victims per type of disaster 1966-1990

Along these lines, floods are to be included within the main natural hazards experienced by our country, taking into consideration the magnitude of their destructive elements, their incidence, the large areas ravaged by these floods and their intensity, affecting the population and disrupting the national economy.

Among the main events that have adversely affected our country, it is worth mentioning the rise of the sea level in 1932, which hit the village of Santa Cruz del Sur, located in the province of Camaguey. As a result, 3,000 people were killed or missing. In addition, the wrongly called “Storm of the Century” in 1993, affected the western and central provinces of Cuba. On this occasion, the sea level rose, particularly on the coast of Havana. In terms of economic losses, this flood is considered the second most significant natural disaster experienced in Cuba.

Floods may be classified as follows:

Flash or rapid floods, and slow or periodic floods.

A very short warning period precede flash floods and, therefore, they represent the main cause of deaths and victims. This type of floods is caused by heavy rainfall, dam breaking, tsunamis or sea surges, resulting in large water masses with a height of up to 6 to 9 meters that ravage large areas.

In terms of morbidity and mortality rates, slow floods only cause a small number of immediate victims.

From sanitary and economic viewpoints, floods represent high risks since they damage both sewer and water supply systems, pollute the environment and spread disease-producing agents, such as mud and oil, as well as other pollutants swept by the water, which affect crops and buildings.

Effects resulting from flooding

We will analyze the effects of these floods according to three main groups:

• Effects on the community;
• Effects on public services; and,
• Effect on the population.

Communities affected by floods could face grave consequences due to the deterioration or destruction of public buildings, schools, hospitals, factories and houses, among others. As a result, public health services may be disrupted, as well as public transportation due to the destruction of roads, bridges and railroads. Furthermore, telecommunications, power, water supply services, solid and liquid waste disposal, water accumulation and debris, make rescue and recovery activities very difficult.
People lose their lives especially because of suffocation by immersion (drowning), injuries, diseases and their consequences. After the flooding, people will have to cope with profound psychological stress due to the loss of their relatives, houses, clothing and supplies, among others.

Experience gained worldwide has shown that floods also increase the potential of transmitting a number of diseases, particularly those derived from inefficient environmental drainage, including water pollution and food contamination, overcrowding and an increasingly number of arthropods and rodents.

Risk factors

After a flood occurs, the risk of transmissible diseases will be determined by the following factors:

• Increasingly morbidity rates with regards to endemic diseases;
• Alterations experienced by the environment;
• Population displacement;
• Changes in population density patterns (overcrowding); and,
• Disarticulation of basic public sanitation services.

It is essential to be aware of which of these factors appear after the flooding, as well as the measures required to control the aforementioned risks. Most likely, and as a result of the interaction between these factors and the population affected, a number of transmissible diseases will increase in short-, mid- and long-terms, depending on their own incubation periods (Table 2).

Table 2
Health-relevant transmissible diseases associated with floods
that may take place within our own environment

Although in general terms specific disease outbreaks are not caused directly by floods, it is possible that the gradual and extended deterioration of basic drainage be translated into health level reduction within communities affected. It is important, therefore, to be aware of which specific diseases increase after the flooding has occurred.

The consequences of these natural disasters include deterioration of the human habitat and, therefore, it must be restored for resettlement purposes. It must be taken into consideration, however, that after the water returns to its intended path geographical changes may occur, leading to population displacement. In some cases, this will be translated into overcrowding or, to a certain extent, relocation, which will influence changes regarding the health status of the population.

General control measures

Experience gained worldwide has shown that, in order to control these problems, two essential action lines must be undertaken.

First, the danger represented by disease spreading may be overcome through appropriate actions in relation to a number of risk factors in the field of public health:

• Water supply with high sanitary quality and quantity for consumption;
• Adequate facilities for sanitary disposal and treatment of excrete and solid and liquid waste;
• Appropriate lodging for displaced people;
• Protection of food against chemical and biological contamination;
• Activities aimed at controlling insects and rodents; and,
• Activities for promoting both personal and collective hygiene.

The second action line includes the establishment of surveillance and warning systems, in order to ensure the epidemiological control of the aforementioned diseases, particularly during their incubation period. For some diseases (such as typhoid fever, hepatitis, leptospirosis and malaria), these control measures must be taken while the population is put up in temporary shelters, but also after they have returned to their homes. In this case, these actions must include all of those who had any type of contact with the population while living in these shelters.

After a natural disaster occurs, mass vaccination for typhoid fever, for instance, is not recommended, given that protective immunity against this disease only lasts a few months. In addition, the effectiveness of this vaccine is relatively low and it may produce different side effects. There is also the risk of transmitting other diseases through vaccination, such as hepatitis and AIDS, and financial and human resources may be allocated inappropriately to this process, with no effective results.

Primary measure

The primary measure to be taken to protect the population at large is an early and adequate evacuation to safer places.

In order to plan potential evacuations, during the first three months of each year, analyses are conducted and forecast carried out by a commission led by the bodies of the Popular Power (Poder Popular) in each municipality. This commission is made up of members of the Civil Defense, CDRs (Committees for the Defense of the Revolution), the Health Administration and MICONS (Ministry of Construction), among others. Vulnerable zones are assessed (taking into account their background, risk maps, etc.), as well as buildings and houses prone to damage (architectural studies). Finally, recommendations are made regarding how families must be evacuated, should this be necessary.

During this planning process prior to a disaster, health authorities are responsible for choosing the nearest safest places to which the population may be evacuated, as well as possible temporary shelters where healthcare and sanitary measures be ensured as general control actions.

Bibliography

• OPS-Salud Ambiental con posterioridad a los desastre naturales. 1982 [PAHO. Environmental Health after Natural Distasters. 1982]
• M. Assar. Guía de Saneamiento en Desastres Naturales. 1971 [M. Assar. Drainage Guidelines regarding Natural Disasters. 1991]
• OPS. Aspectos Administrativos de Salud. Volumen 2, 1983. [PAHO. Health Administrative Aspects. Volume 2, 1983]
• OPS. Vigilancia Epidemiológica con posterioridad a los desastres naturales. 1982 [PAHO. Epidemiological Surveillance after Natural Disasters. 1982]
• John Reaman. Epidemiología de desastres naturales . México: Editorial Hala, 1989. [John Reaman. Epidemiology of Natural Disasters. Mexico: Hala Publishers, 1989

For further information, please contact:
Dr. Vicente García
pmmsp@infomed.sld.