Natural disaster is a calamitous event that is caused by nature. It is an event with atmospheric, geologic, and hydrologic origins. Disaster mainly includes volcano, earthquake, floods, droughts and landslides. In past 2 decades natural disaster has killed millions of people, has affected billions of lives and trillions of economic damage.
Natural disaster can mainly be divided in 3 categories: geophysical disasters (e.g. earthquake), hydro-meteorological disasters (e.g. floods, typhoons) and geomorphologic disasters (e.g. landslides, avalanches)
After natural disaster
In recent years, the magnitude of natural disasters has grown which results in the economic damages, affecting and killing millions of people. The risk of infectious disease outbreak in the aftermath of natural disasters has usually been overemphasized by health officials and media, which leads to panic confusion and unnecessary public health activities.
Most people believe that there is high risk of communicable diseases outbreaks shortly after natural calamities. But this has not been scientifically proven, unless there is huge population displacement. As we know there is sudden increase in dead bodies after the disaster, this leads the concern of disease outbreaks. There is no such evidence that dead bodies pose a risk for epidemics when death is directly due to the natural disaster. Dead bodies could be a risk factor and proper precautions must be taken when the death is due to cholera or hemorrhagic fever. Again, several synergic factors including massive population displacement, and change in environment, as well as the vulnerability to existing pathogens can cause the outbreaks.
Management of dead bodies as given by CDC is given in Table.
Phases of Outbreak
Infectious disease starts transmitting after some days, weeks or sometimes even months of the disaster. Mainly there are 3 clinical phases of natural disasters summarize the chronological public health effects on injured people and survivors:
Phase 1: Also known as impact phase, lasts up to 4 days, in this period victim are removed and initial treatment of disaster related injuries is provided.
Phase 2: Also known as post impact phase; lasts from 4 days to 4 weeks, there is high chances of emergence of infectious diseases like air borne, food borne/ water borne.
Phase 3: Also known as the recovery phase; it is after 4 weeks. In this period infectious diseases that are already endemic in the areas and newly imported diseases around the community may turn into an epidemic.
Diseases associated with the Natural Disasters
Water borne diseases
After natural disaster, there is very less chance to get safe water. The major risk factor for outbreaks associated with flooding is the contamination of drinking water facilities. After flood there are high chances of outbreak of diarrheal diseases. There are evidences from many countries like Indonesia (1992-1993), Mozambique (2000) West Bengal (1998) having increased cases of illness caused by Salmonella enterica serotype Paratyphi , diarrhea and cholera epidemic (O1 Ogawa). These entire diarrheal diseases outbreak is higher in developing countries than developed countries.
In Iran, about 75586 persons displaced by the Bam earthquake in 2003 were infected with diarrheal diseases. Haiti was reported cholera epidemic after 9 months of the earthquake.
Hepatitis A and E are also transmitted by fecal-oral route. After the 2005 earthquake in Pakistan, sporadic hepatitis E cases In Aceh both hepatitis A and E were noticed after the tsunami of 2004.
Vector borne diseases
Natural disasters, mainly cyclones, hurricanes and flooding affects vector=breeding sites and vectorborne disease transmission. Firstly all these calamities may wash away all the mosquito-breeding sites but later leading to outbreaks. Flood may lead to increase in vector borne diseases through the expansion in the number and range of vector habitats. Many mosquitoes breeding habitat is stagnant water, hence stagnant water formed after flood becomes the breeding site for mosquitoes hence increase the outbreaks of dengue, malaria, yellow fever. For example West Nile fever was a major outbreak in Romania (1996-97), in Czech Republic (1997) and in Italy (1998) because of subsequent heavy rains and flooding.
Diseases associated with crowding
Population gets displaced after natural disasters. This leads to crowding and can facilitate the transmission of infectious diseases. Measles, Neisseria meningitis are most commonly transmitted as the result of overcrowding. Acute respiratory Infections (ARI) are a major cause of illness among displaced populations mainly in children under 5 of age. Lack of health facilities for treatment after the natural disaster, further increases the risk of death from ARI.
Prevention and control measures of diseases
Safe water and Sanitation
As we know after most of the natural disasters there is always the chance of contamination of water resources. Providing safe drinking water is the most important preventive measure following natural resources. Hygienic environment must be maintain, focus to the sanitation must also be given.
Primary health-care facilities
Primary health care facilities must be accessed for the prevention, early diagnosis and treatment of a wide range of diseases, as well as providing an entry point for secondary and tertiary care. Early diagnosis and treatment for diarrheal diseases, ARI, malaria (in endemic areas) must be provided. For to prevent tetanus, there must be proper wound cleaning and care. Educating people about the infectious diseases and how to tackle them must go side by side. Ensure the availability of drugs and emergency health kit. Vector control interventions must be adapted. Rapid detection of cases of epidemic –prone diseases is very much essential. Hence surveillance warning system should be established.
Mass immunization of Measles with vitamin A is immediate health priorities following natural disasters in areas with inadequate coverage. Vaccination for Typhoid, Hepatitis A and Cholera are not mostly recommended to prevent outbreaks in disaster area but sometimes can be helpful.
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