Flooding and Communicable Diseases Fact Sheet - WHO Risk aAssessment Floods can potentially increase the transmission of the following communicable diseases: - Water-borne diseases, such as typhoid fever, cholera, leptospirosis and hepatitis A - Vector-borne diseases, such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever Water-borne 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 only 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. Vector-borne Diseases 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 West Nile fever. Flooding may initially flush out mosquito breeding, but it comes back when the waters recede. The lag time is usually around 6-8 weeks before the onset of a malaria epidemic. The risk of outbreaks is greatly increased by complicating factors, such as changes in human behaviour (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). Other Health Risks posed by Flooding • These include drowning and injuries or trauma. Tetanus is not common after injury from flooding, and mass tetanus vaccination programs are not indicated. However, tetanus boosters may be indicated for previously vaccinated people who sustain open wounds or for other injured people depending on their tetanus immunization history. Passive vaccination with tetanus immune globulin (Hypertet) is useful in treating wounded people who have not been actively vaccinated and those whose wounds are highly contaminated, as well as those with tetanus. • Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods. There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). • Power cuts related to floods may disrupt water treatment and supply plants thereby increasing the risk of water-borne diseases as described above but may also affect proper functioning of health facilities, including cold chain. Preventive Measures Communicable disease risks from flooding can be greatly reduced if the following recommendations are followed. Short-term Measures Chlorination of Water Ensuring uninterrupted provision of safe drinking water is the most important preventive measure to be implemented following flooding, in order to reduce the risk of outbreaks of water-borne diseases. • 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). • The amount of chlorine needed 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. Vaccination against Hepatitis A • The use of hepatitis A vaccines for mass immunization is not recommended. • Vaccination of high-risk groups, such as persons involved in the management of drinking water, waste water or sewage might be considered. • In case of an outbreak of hepatitis A consider immunization of contacts. The use of immunoglobulins is not recommended. • Diagnosis of acute hepatitis A is confirmed by anti-HAV IgM antibodies. Malaria Prevention • Insecticides: flooding does not necessarily lead to an immediate major increase in mosquito numbers, and there may still be time to implement preventive measures such as indoor residual spraying, or the retreatment/distribution of ITNs in areas where their use is well-known. This will also have an effect on other mosquito-borne diseases. • Early detection: it is important to track weekly case numbers and provide laboratory-based diagnosis (perhaps only for a % of fever cases to track the slide/test positivity rate), to pick up the early stages of a malaria epidemic. • Free medical care: with artemisinin-based combination therapy should be provided when a falciparum malaria epidemic is confirmed, and an active search for fever cases may be necessary to reduce mortality in remote areas with reduced access to health care services. Health Education • Promote good hygienic practice. • Ensure safe food preparation techniques. • Ensure boiling or chlorination of water. • Vital importance of early diagnosis and treatment for malaria (within 24 hours of onset of fever). Long term Measures Legislative/Administrative Issues • Create Disaster-Preparedness Programmes and Early Warning Systems. • Improve surveillance on a local, national, international and global level. • Promote tap-water quality regulation and monitoring. • Enforce high standards of hygiene. Technical Issues • Improve water treatment and sanitation. • Keep infectious disease control programmes active and efficient. PREPARATION AND AWARENESS IS THE KEY... DO NOT BE A VICTIM! Rino
Posted on: Tue, 18 Jun 2013 03:50:54 +0000
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