A boy feeds his younger brother at a temporary shelter after fleeing cyclone-hit areas in the Irrawaddy division of Myanmar on Thursday. Here are the health questions and answers in the aftermath of cyclone Nargis that slammed Myanmar recently: What is the main health risk after the cyclone? The primary risk following the flooding of the delta region is the outbreak of diseases spread by contaminated water, such as diarrhoea, cholera and typhoid. Aid agencies on the ground report that flooding and broken pipes have allowed sewage, toxins and groundwater into the water supply. Lakes, rice paddies and streams are also dirty because they are littered with corpses. Stagnant water is providing a breeding ground for bacteria and mosquitoes. According to Save the Children, more than a third of deaths in previous similar disasters have been caused by waterborne diseases. Which diseases pose the most immediate threat? Initially, the most likely killer is acute watery diarrhoea, which causes dehydration. Those most at risk are under-fives, the sick, the old and the pregnant. Cholera, which causes severe diarrhoea and vomiting, is the next major worry. In severe cases people suffer progressive organ failure as they get weaker. It can spread rapidly in areas where there is poor sanitation because the bacterium can be spread in human faeces. There are already reports of an outbreak in the Irrawaddy delta. Other threats include typhoid and hepatitis A, both passed on by contaminated food and water. Symptoms of the former include fever, abdominal pain, appetite loss, constipation or diarrhoea. Without treatment it is fatal in 10 per cent of cases. What about later on? Within two weeks there could be outbreaks of malaria and dengue fever, which are spread by mosquitoes. The malaria parasite infects the liver. It initially causes flu-like symptoms. There can also be diarrhoea, coughing and jaundice. Without treatment it can kill by causing anaemia and by clogging the capillaries that carry blood to the brain or other vital organs. Another threat is posed by dengue fever, which is endemic in Myanmar. Symptoms include fever, joint and muscle pain, nausea and vomiting. Some people develop severe bleeding known as dengue haemorrhagic fever, which can be fatal. There is no specific treatment, though most people recover in two weeks. What other health risks are there? Survivors also risk contracting tetanus and infections from injuries as they rummage through their destroyed homes. Overcrowded conditions in shelters for homeless survivors often also lead to outbreaks of childhood diseases such as measles, mumps, rubella, whooping cough and chicken pox. Women are also at risk of vaginal infections caused by wading through polluted water. This can cause infertility. What can be done to address the risks? Immediate efforts are focused on restoring water supplies and sanitation. Unicef is sending three million water purification tablets to Myanmar, sufficient for five million litres of water