Health impacts of flooding and risk management
Floods are common natural disaster occurring worldwide. India is the most flood prone country in the world and accounts for one fifth of global deaths by floods. The main reasons for floods in India are high intensity rainfall in short duration, poor or inadequate drainage capacity of rivers, unplanned reservoir regulation and failure of flood control structures. Floods cause huge losses to lives, properties, livelihood systems, infrastructure, public health and healthcare system.
The natural events cannot be prevented but their impact can be mitigated. Emphasis has been shifted from disaster response to risk management, including the improvement of flood forecasting and warning systems with the addition of health protection during response and recovery phase.
Establishment of Early Warning Alert and Response Network (EWARN)- The EWARN system is an enhancement of the existing routine syndromic surveillance system during and after disaster which is implemented by the Integrated Disease Surveillance Programme under Ministry of Health and Family Welfare , Government of India.
Health impacts of flooding and risk management
The immediate health impacts of floods include drowning, injuries, hypothermia, and animal bites. Health risks are also associated with the evacuation of patients, loss of health workers, and loss of health infrastructure including essential drugs and supplies.
Floods can potentially increase the transmission of the following communicable diseases:
There is an increased risk of infection of water-borne diseases contracted through direct contact with polluted waters, such as wound infections, dermatitis, conjunctivitis, and ear, nose and throat infections. However, these diseases are not epidemic-prone.
The major risk factor for outbreaks associated with flooding is the contamination of drinking-water facilities resulting into water borne diseases such as typhoid fever, cholera, leptospirosis and hepatitis A.
The epidemic-prone infection which can be transmitted directly from contaminated water is leptospirosis, a zoonotic bacterial disease. Transmission occurs through contact of the skin and mucous membranes with water, damp soil or vegetation (such as sugarcane) or mud contaminated with rodent urine. The occurrence of flooding after heavy rainfall facilitates the spread of the organism due to the proliferation of rodents which shed large amounts of leptospires in their urine.
Following measures can be taken to prevent communicable diseases from flooding:
Prevention of water-borne diseases:
1.Ensuring uninterrupted provision of safe drinking water: It is the most important preventive measure to be implemented following flooding, in order to reduce the risk of outbreaks of water-borne diseases. Chlorination of water is effective method for disinfecting drinking water.
Chlorination is the process of adding chlorine to drinking water to disinfect it and kill germs. Different processes can be used to achieve safe levels of chlorine in drinking water. Chlorine is available as compressed elemental gas, sodium hypochlorite solution (NaOCl) or solid calcium hypochlorite -Ca(OCl)2.
The amount of chlorine required depends mainly on the concentration of organic matter in the water and has to be determined for each situation. After 30 minutes, the residual concentration of active chlorine in the water should be between 0.2-0.5 mg/l, which can be determined using a special test kit.
Free chlorine is the most widely and easily used, and the most affordable of the drinking water disinfectants. It is also highly effective against nearly all waterborne pathogens (except Cryptosporidium parvum oocysts and Mycobacteria species). At doses of a few mg/litre and contact times of about 30 minutes, free chlorine generally inactivates >99.99% of enteric bacteria and viruses.
For point-of-use or household water treatment, the most practical forms of free chlorine are liquid sodium hypochlorite, solid calcium hypochlorite and bleaching powder (chloride of lime; a mixture of calcium hydroxide, calcium chloride and calcium hypochlorite).
3. Prevention of leptospirosis
Floods may indirectly lead to an increase in vector-borne diseases through the expansion in the number and range of vector habitats. Standing water caused by heavy rainfall or overflow of rivers can act as breeding sites for mosquitoes, and therefore enhance the potential for exposure of the disaster-affected population and emergency workers to infections such as dengue, malaria and other vector borne diseases.
Flooding may initially flush out mosquito breeding, but it comes back when the waters recede. The lag time is usually around 3-4 weeks before the occurrence of dengue cases and 6-8 weeks before the onset of a malaria epidemic.
Malaria epidemics in the wake of flooding are a well-known phenomenon in malaria-endemic areas world-wide. The risk of outbreaks is greatly increased by complicating factors, such as changes in human behavior (increased exposure to mosquitoes while sleeping outside, a temporary pause in disease control activities, overcrowding), or changes in the habitat which promote mosquito breeding (landslide, deforestation, river damming, and rerouting).
Rapid and appropriate precautionary vector-control measures applied in a post-natural disaster setting can prevent vector borne diseases.
Prevention of vector borne diseases:
Flooding can have effects on people’s mental health and well-being. Most people can cope the situation while few people may develop mental health problems. The effects of being separated from family and friends, disruption to family life and daily routine and the loss of pets and possessions, moving to temporary accommodation, all can have an effect on mental health of children.
Symptoms can include: separation anxiety; irregular sleeping patterns / nightmares; behavioural problems such as becoming withdrawn, increased aggression, bedwetting; development of habit forming behaviours such as routines / rituals about washing and academic performance may suffer.
Psychological first aid can be provided by field workers, including health workers, teachers or trained volunteers, and does not always need mental health professionals. However psycho-social teams (psychiatrist, psychologists and psycho-social worker) may be needed for rapid psycho-social assessment and community based psycho-social care and referral services in affected community.
During flooding water enters the nesting holes of snakes, and forcing them to come out in the open. The snakes then start looking for dry areas and may, unfortunately, come into close contact with humans inside their houses, hence the incidence of snake bites increase after flooding.
Prevention from snake bite