Bangkok Post : The risk factor

by Symptom Advice on November 29, 2011

Aside loss to life and property, flooding also spawns an increased risk of infection due to exposure to contaminated and polluted waters. the prolonged flooding, now in its third month, has sparked an outbreak of infectious diseases in various parts of Thailand both from direct and indirect transmission. These diseases can be broadly divided into two major categories: viz, water-borne such as typhoid fever, cholera, leptospirosis and hepatitis a, and vector-borne such as malaria, dengue and dengue haemorrhagic fever.


Floods may indirectly lead to an increase in vector-borne diseases through the rapid increase in vector numbers due to expansion of their breeding sites. Stagnant water collecting in pools after heavy rainfall or overflow of rivers are breeding sites for mosquitoes, and therefore can put people and emergency workers in flood areas at higher risk of contacting dengue and malarial infection.


The number of mosquitoes may decrease at the beginning of flooding as the water flushes out mosquito larvae, but their population quickly expands after a lag time which is usually around 6-8 weeks, before the onset of a malaria epidemic.

Risk factors for an epidemic include:

- Changes in human behaviour such as avoiding using mosquito nets or insect repellent, lack of information about infectious diseases associated with flooding and high population densities in emergency centres are all examples of risk factors with potential to cause an epidemic.

- a change in environment resulting from, say, construction of roads and buildings, water reservoirs or as a result of deforestation have corresponding effect on the breeding sites and habits of these vector-borne insects.


Dengue is transmitted by the bite of an Aedes mosquito infected with dengue viruses. Patients infected with the virus will show symptoms approximately one week after the infective bite. Symptoms can range from a mild fever (dengue), to a severe incapacitating high fever with blood vessels becoming temporarily “leaky” (dengue hemorrhagic fever: DHF) or a deadly form of the disease that causes the patient to go into shock and die (dengue shock syndrome: DSS), seen in 80%, 15%, and 5% of the cases.

Major symptoms range from high fever that can last 2-7 days, skin bleeding, enlarged liver, abdominal pain, and failure of blood circulation leading to a state of shock. the most dangerous stage is the failure of hemodynamic which occurs simultaneously with rapid decline of fever. If the patient does not receive proper medical attention in a timely manner, the conditions will continue to deteriorate, and death is possible within 12-24 hours after entering the state of shock.

While there are no specific antiviral medicines for dengue, early diagnosis and proper clinical management by experienced physicians can significantly lower the mortality rate.

1. Physician may prescribe antipyretic agents to lower high fever to prevent seizure in some patients. Use of acetylsalicylic acid (eg aspirin) and non-steroidal anti-inflammatory drugs (eg Ibuprofen) are not recommended as they cause stomach bleeding.

2. Maintain adequate hydration in patients with high fever.

3. Monitor patients closely to detect and prevent shock.

4. Periodically check the change in platelet count and hematocrit.

For patients who experience shock or bleeding, doctor will need to provide specialised treatments using plasma fluid or colloid substance to save the patient’s life and prevent other complications that may occur.

“Lowering mosquito numbers and minimising exposure to bites are important. Mosquito breeding sites must be removed, destroyed, frequently emptied and cleaned or treated with insecticides. during epidemics spray insecticide regularly to kill adult mosquitoes.

- Early diagnosis and treatment: Monitoring laboratory confirmed cases every week allows us to detect malaria outbreak at the early stage.

- Monitoring the population of patients with fever and providing them with proper medical care in a timely manner can significantly reduce the rate of death from dengue hemorrhagic fever and malaria.

- Providing health education, promoting good hygiene and eating habits, and offering critical advice about dengue hemorrhagic fever and its symptoms can pave the way for early detection and treatment.


It is caused by the bacteria Leptospires that affects both humans and animals. Humans become infected through direct contact with the urine of infected animals especially rodents or with a urine-contaminated environment.


Leptospirosis is an occupational hazard for people who work outdoors or with animals and must stay in water for prolonged periods, such as farmers and sewer workers. it is also a recreational hazard to those who swim or wade through waters contaminated with the bacteria, which can gain entry through cuts and abrasions on the skin and through the mucous membrane in the eyes, nose and mouth.


Three to 10 days after infection patients experience acute fever, severe headache, muscle pain, chills, redness of the eyes, abdominal pain, jaundice, haemorrhages in the skin and mucous membranes, vomiting, diarrhoea, and rash.

These symptoms normally occur after wading through muddy water for prolonged periods (average 10 days). Patients need to seek medical care immediately. Do not try to treat yourself with any medicine.


Avoid walking through dirty or muddy water especially when having sustained cuts or wounds in hands, arms, legs and feet without wearing protective gear, such as gloves and boots. Bathe immediately after wading through floods. Keep your accommodation and surrounding areas clean to control the spread of infection source (eg rodent and garbage control); eat properly and only cooked food; and store food in clean containers with protective covers.

Bangkok Health Research Center, Bangkok Hospital Group, call 1719.

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