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Infectious disease risks rise from flood water mixed with sewage
View(s):By Nathara Abeywickrema
As floodwaters recede following several days of heavy rain across several districts, health officials have raised an urgent alarm over the increased risk of infectious diseases.
Flood-affected areas, especially those where stagnant water remains, are now highly vulnerable to the spread of both water-borne and vector-borne diseases. With public health at stake, officials are calling for immediate preventive measures to minimise potential outbreaks.
The receding floodwaters leave behind pools of stagnant water, sewage, and debris, creating an environment ripe for the spread of disease. According to Dr. Thilanga Ruwanpathirana, a consultant epidemiologist of the Ministry of Health, the main concerns are water-borne illnesses such as cholera, typhoid, diarrhoea and food poisoning.
“When floodwaters mix with sewage systems and untreated water sources, the risk of contamination skyrockets,” he said. He noted that even minor exposure to contaminated water put the health of children and the elderly at risk.
Residents in flood-affected areas are urged to boil drinking water and practice proper hand hygiene to curb the spread of diseases. “Boiling water is one of the simplest yet most effective ways to kill bacteria and viruses that can cause severe gastrointestinal illnesses,” Dr. Ruwanpathirana said.
In addition to water-borne diseases, the threat of dengue fever has sparked concern among health professionals. Standing water provides ideal breeding grounds for mosquitoes, particularly the dengue-carrying Aedes mosquito.
Dr. Lahiru Kodithuwakku, a medical officer attached to National Dengue Control Unit (NDCU), warned of a surge in dengue cases in the next few weeks, if preventive measures are not taken.
“Mosquito breeding is likely to intensify as the floodwaters begin to stagnate. Dengue outbreaks are a real possibility unless communities take immediate action to eliminate breeding sites,” he said.
Health officials have already initiated vector control measures in flood-affected areas such as Kaduwela and Hanwella in the Colombo district, as well as Kelaniya and Dompe in the Gampaha district. Also, from October 24 to 26, dengue prevention programmes will be launched across 28 MOH areas in the Northern and Eastern provinces to prevent potential outbreaks with the onset of the North-East monsoon.
However, Dr. Kodithuwakku said community participation is critical. “Everyone must play a role. Disposing of discarded containers, tyres, and other water-collecting items is crucial to stopping mosquitoes from breeding.’’
He advised seeking prompt medical attention especially if presenting with symptoms such as fever, headache, or joint pain. While paracetamol (acetaminophen) is recommended for relieving pain and fever, he cautioned against using aspirin, ibuprofen, or other salicylates and nonsteroidal anti-inflammatory drugs (NSAIDs).
Health authorities are also warning of an increase in leptospirosis, commonly known as ‘rat fever’, a year-round concern in Sri Lanka. It is spread through water contaminated by the urine of infected animals, mainly rodents.
Flooding displaces rodents from their burrows and drains, increasing the risk of widespread contamination. The disease peaks twice annually during the March to May monsoon season and again from October to December, with a larger spike expected following floods, making preparedness essential, cautioned Dr. Thushani Dabrera, consultant community physician with the Epidemiology Unit.
The long-term impacts of leptospirosis are significant, especially as it affects economically active populations like farmers, leading to financial strain and severe health consequences such as liver and kidney damage, she added.
Dr. Dabrera advised that to prevent infection, people should avoid walking in floodwaters, keep animals away from play areas, wear protective clothing and footwear, cover wounds in waterproof dressing when walking in flood waters, use boiled water, and maintain cleanliness to control rodents.
The government has established a steering committee to coordinate prevention efforts, raise public awareness, and provide prophylactic antibiotics to high-risk groups such as paddy farmers and those affected by floods, Dr. Dabrera said.
Another serious concern is the state of sanitation in temporary shelters for displaced residents. Overcrowding and limited access to clean water and sanitation facilities can lead to outbreaks of diseases such as skin diseases, respiratory infections, and dysentery.
PHI Union secretary Chamil Muthukuda overseeing relief efforts in one of the worst-hit areas, expressed his concerns: “We are seeing increasing numbers of displaced individuals in makeshift shelters, where maintaining proper hygiene is a challenge.
“Efforts are also underway to improve waste management in flood-affected areas to mitigate the spread of infectious diseases. We advise the public to temporarily avoid consuming leafy vegetables, as they may be contaminated by floodwaters.’’
In addition to vector-borne diseases, there has been a noticeable increase in patients suffering from influenza, diarrhoea, and upper respiratory tract infections, particularly in flooded areas. The mixing of floodwaters with sewage and other contaminants can lead to gastrointestinal illnesses, worsening the health crisis, said Dr Deepal Perera, consultant paediatrician of Lady Ridgeway Hospital for Children.
“Floodwater often mixes with sewage, making drinking water unsafe, which can lead to severe gastrointestinal illnesses in children,” he explained. Also, respiratory infections are likely to increase in overcrowded shelters, where viral infections spread more easily, he cautioned.
To prevent dehydration from diarrhoea, both children and adults are advised to use oral rehydration salts (such as Jeevanee) and consume natural fluids like king coconut water. They recommend avoiding papaya and butter if diarrhoea persists. Eating bananas can help manage gastrointestinal issues due to their binding effect.
Dr. Perera emphasised the importance of children’s nutrition and being hydrated.
As the flood crisis subsides, health officials are looking ahead to the long-term public health challenges that may arise.
Dr. Perera stressed that alongside relief efforts, continuous public health campaigns aimed at prevention and awareness are just as vital. “The weeks following floods are often the most critical. Communities need to stay vigilant and take the necessary precautions to avoid preventable disease outbreaks,” he noted.
Officials are urging the government to prioritise improvements in drainage and sanitation infrastructure to to prepare for any future flooding events. Health officials say that “inadequate drainage and waste management systems are significant contributors to the increased disease risks after floods. It is crucial to address these issues to develop effective long-term solutions.”
People are advised to monitor any symptoms of infection and seek medical attention at the first sign of illness. In particular, those with high fever, vomiting, persistent diarrhoea, or skin rashes should be evaluated by a healthcare professional.
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