… Contaminated floodwaters, blocked drainages heighten cholera, typhoid, malaria risks
…Urge govts to strengthen surveillance, stock medicines before deaths rise
By Chioma Obinna
The floodwaters that swept through Lagos and several parts of Nigeria in recent weeks left behind more than submerged homes, impassable roads and ruined livelihoods.
Across communities battered by relentless rainfall, families watched helplessly as muddy water invaded their homes, traders counted heavy losses after shops and markets were inundated, motorists abandoned vehicles trapped on flooded roads, while thousands of commuters waded through waist-deep water simply to get to work or return home. For many residents, every dark cloud now brings fresh anxiety.
But public health experts warn that the greatest danger begins after the floodwaters recede.
Beyond the visible destruction lies a looming public health emergency as contaminated water, poor sanitation, blocked drainage systems and climate change create ideal conditions for outbreaks of cholera, typhoid fever, malaria and other infectious diseases.
A Consultant Public Health Physician at the Lagos State University Teaching Hospital (LASUTH), Dr. Adedayo Aderibigbe, described flooding as far more than an environmental disaster.
“The health crisis begins after the flood,” he warned.
According to him, while public attention is often fixed on submerged roads and damaged property, the real crisis emerges after the water begins to disappear.
“We have seen repeated flooding disrupting human lives and livelihoods. Houses are flooded, streets are flooded and businesses are disrupted. People are displaced from their homes and lose their means of livelihood. Apart from the physical destruction, flooding also creates emotional trauma because people suddenly lose their homes, their possessions and their sense of security.”
Aderibigbe said many of Nigeria’s floods are made worse by human activities.
“We clog our drainage channels. We fail to clear them regularly. People dump refuse indiscriminately and others build on natural waterways. When the rain comes, the water has nowhere to go.”
He said these practices continue to undermine government efforts to reduce flooding despite investments in drainage infrastructure.
“The government has provided drainage channels in many places, but people block them with refuse. If water cannot pass through the channels created for it, it inevitably finds its way into homes, roads, and businesses.”
According to him, the visible flood is only one part of the disaster.
The greater threat lies in what the floodwaters carry.
The invisible enemy in floodwater
Every flood, Aderibigbe explained, turns contaminated waste into a moving public health hazard.
“The floodwater people wade through is not just rainwater. It carries sewage, refuse, human waste and disease-causing organisms capable of spreading infections across entire communities.”
He identified cholera as the most immediate threat.
“One of the commonest diseases we expect after flooding is cholera. There is virtually no year Nigeria does not record cholera deaths.”
According to him, widespread open defecation worsens the danger because floodwaters easily carry human faeces into wells, streams, food sources, and drinking water.
“When people defecate in open places, floodwater carries the faeces from one location to another. Nobody can predict how far contaminated faeces will travel. It contaminates wells, streams, food and drinking water. That is why cholera outbreaks become common during the rainy season.”
He said cholera is only one of several diseases that flourish after flooding.
Typhoid fever, diarrhoeal diseases, food poisoning and malaria also increase as contaminated water comes into contact with food, while stagnant pools become breeding grounds for mosquitoes.
He warned that contaminated food is another overlooked source of infection.
“A lot of people buy fruits every day without knowing the quality of the water used to wash or sprinkle them before they are displayed for sale. People simply buy and eat them without washing them properly. That is another route through which infections spread.”
The same risk, he said, applies to vegetables and other foods exposed to contaminated floodwater.
Why malaria and other diseases surge
Beyond cholera and typhoid, Aderibigbe said flooding creates ideal breeding conditions for mosquitoes.
“The mosquito prefers stagnant water. Whenever floodwater remains instead of flowing away, mosquitoes lay their eggs there. That is why malaria cases increase after flooding.”
Without prompt environmental sanitation, he warned, mosquito populations can rise rapidly, exposing already vulnerable communities to additional health risks.
This is not the time to wait for deaths
Aderibigbe said Nigeria must stop responding to outbreaks only after lives have been lost.
“This is not the time to wait until people start dying. This is the time to activate surveillance.”
He urged health authorities to intensify disease surveillance from community to state level to detect unusual increases in cholera, diarrhoeal diseases and other water-related infections before they become major outbreaks.
“We already know the diseases that are likely to increase after flooding. This is the period when surveillance systems should be fully active.”
He also called on hospitals and primary healthcare centres to prepare ahead of any surge in cases.
“Hospitals should already be stocking antibiotics and other essential medicines. Once outbreaks begin, demand for treatment increases immediately.”
According to him, early preparedness remains the most effective way to save lives.
Beyond awareness to enforcement
While public education is essential, Aderibigbe argued that enforcement of environmental laws is even more critical.
“There is one thing to educate people and another thing for people to obey.”
He urged the Ministry of Environment and other agencies to ensure drainage channels remain free of refuse and to sanction indiscriminate dumping.
“Many people dump refuse into drainages in the dead of the night. By morning, the channels are blocked.”
He believed stronger enforcement alone could drastically reduce annual flooding.
“If drainage channels are properly cleared and allowed to function the way they were designed, flooding can be reduced by about 50 per cent.”
He also criticised the indiscriminate construction of buildings on waterways, urging planning authorities to enforce city master plans and insist on Environmental Impact Assessments before approving major developments.
“We already have agencies responsible for these things. They simply need to enforce the rules.”
Preparedness must be matched with response
Although he commended Lagos State for investing in flood preparedness and public sensitisation, Aderibigbe said preparedness alone is not enough.
“There is a difference between preparedness and response.”
He explained that once cases of cholera or other waterborne diseases are detected, health authorities must move swiftly with surveillance, community alerts and public education to stop transmission.
“Our surveillance systems must work effectively. Once cases begin to appear, the response should be immediate.”
Protecting families
Aderibigbe urged residents of flood-prone communities to heed official flood warnings and relocate temporarily whenever necessary.
“Government is not trying to displace people. It is trying to save lives.”
He advised Nigerians to avoid walking through floodwater where possible and to wash thoroughly with clean water and soap after any contact.
Residents should also boil drinking water from doubtful sources, wash fruits and vegetables thoroughly, cook food properly and maintain good hand hygiene.
“Anything that goes into your mouth, whether food or water, must be safe during this period.”
Who is most at risk?
According to him, the most vulnerable are residents of flood-prone communities, low-income households and families without reliable access to safe drinking water.
“They are more likely to depend on unsafe water sources and have fewer options when flooding disrupts their communities.”
He said protecting these groups requires more than emergency relief. It demands stronger environmental enforcement, improved urban planning, better access to safe water, a prepared health system and sustained public education.
For the Executive Secretary of the Nigerian Academy of Science (NAS) and former Chairman of the Association of Public Health Physicians of Nigeria, Lagos Chapter, Dr. Doyin Odubanjo, said the crisis begins even before the first case of cholera is reported.
According to him, the first casualty of every flood is peace of mind.
Flooding first creates anxiety
“Flooding is happening across the world, but the first thing it brings is disruption,” Odubanjo said.
“People begin to ask themselves: ‘Will the water get into my house? Will I be able to go to work? Will I get to the market? Will I keep my appointments? Will I earn an income today?’”
He said the uncertainty surrounding floods creates enormous psychological pressure, especially for families whose livelihoods depend on daily income.
“If you are a taxi driver and the roads are flooded, you cannot work. That means no income. If you cannot get to your shop or market, your livelihood is disrupted. Those are public health issues because they affect people’s mental wellbeing.”
Nigeria, he noted, often overlooks the mental health burden associated with disasters.
“We tend to neglect mental health, but anxiety is a serious health problem. Some people become overwhelmed by fear and uncertainty after flooding.”
Everything gets mixed during floods
Beyond the emotional toll, Odubanjo described flooding as one of the quickest ways to contaminate an entire community.
“Everything gets mixed during floods.
Clean water is no longer separated from dirty water. Waste is no longer separated from drinking water. If you have a well and it becomes flooded, what exactly are you fetching from that well afterwards?”
According to him, floodwaters mix sewage, refuse and human waste with water sources, exposing entire communities to dangerous infections.
“We still have open defecation in many places. Human waste is washed into floodwater, and that contaminated water comes into contact with homes, food, and drinking water.”
He warned that many people unknowingly expose themselves to harmful organisms simply by walking through contaminated floodwater.
Disease outbreaks become inevitable
Once floodwater becomes contaminated, Odubanjo said, disease outbreaks are rarely far behind.
He identified cholera, typhoid fever, diarrhoeal diseases and other gastrointestinal infections as the illnesses health authorities should expect after major floods.
“These are the diseases we worry about because they spread through contaminated water.”
Flooding also creates ideal breeding sites for mosquitoes, increasing the risk of malaria.
“If water is no longer flowing through its proper channels and becomes stagnant, mosquitoes multiply rapidly.”
He added that flies further worsen the situation by carrying disease-causing organisms from contaminated waste onto exposed food.
“You may chase a fly away from your food, but by then it may already have deposited harmful organisms.”
Beyond disease: A food security challenge
Odubanjo said the consequences of flooding extend beyond public health to food security and nutrition.
“When farms are flooded, crops are destroyed. Food is lost.”
He warned that families who lose their harvests or sources of income may struggle to afford nutritious meals, increasing the risk of malnutrition, particularly among children.
For this reason, he argued, flooding should no longer be viewed solely as a seasonal environmental problem but as a public health and socioeconomic emergency requiring coordinated action across multiple sectors.
What Nigerians should do
While stressing that government has a major responsibility, Odubanjo urged Nigerians to take simple but effective steps to protect themselves after flooding.
He advised households to treat every source of drinking water with caution.
“If I am taking water after flooding, I will boil it. If necessary, I will disinfect it because I no longer have the same confidence in that water source.”
He also urged residents to maintain good personal hygiene, wash food thoroughly, eliminate stagnant water around their homes and use insecticide-treated mosquito nets to reduce the risk of malaria.
“People must pay closer attention to food hygiene because contamination becomes much easier after floods.”
Government must act quickly
According to Odubanjo, public education should be the first line of response whenever flooding occurs.
“The first responsibility of government is to educate people.”
He said communities should receive timely information on safe water, food hygiene, mosquito control and the early symptoms of waterborne diseases.
Beyond awareness campaigns, he urged authorities to quickly clear blocked drainage channels, repair damaged water infrastructure and strengthen water treatment where flooding may have contaminated public supplies.
“In situations like this, government may even need to increase water treatment to ensure communities receive safe drinking water.”
Protect the most vulnerable
Odubanjo called for targeted interventions for people most at risk, particularly those living in displacement camps and overcrowded communities where access to clean water and sanitation is limited.
“There is an oral cholera vaccine. You do not vaccinate everybody, but people living in high-risk conditions should receive that extra layer of protection.”
He said such preventive measures could significantly reduce illness and deaths during emergencies.
Health system must stay ahead
Odubanjo urged health authorities to anticipate a rise in cholera, typhoid, diarrhoeal diseases and malaria following major floods instead of waiting for outbreaks to escalate.
Hospitals and primary healthcare centres, he said, should remain on high alert, while surveillance teams monitor communities for early signs of disease transmission.
“It is always better to prevent an outbreak than to struggle to contain one.”
Beyond the flood
Although Aderibigbe and Odubanjo approached the issue from different perspectives, their message was the same: the flood itself is only the beginning.
They warned that Nigeria’s annual floods have evolved into recurring public health emergencies driven by climate change, poor urban planning, blocked drainage systems, weak environmental enforcement and unsafe sanitation practices.
The experts argued that preventing the next disaster will require more than emergency relief after homes and roads have been submerged. It demands year-round investment in drainage infrastructure, enforcement of environmental and building regulations, improved access to safe water, stronger disease surveillance, well-equipped health facilities and sustained public education. Because when the floodwaters recede, they leave behind more than damaged homes and ruined livelihoods.
They leave contaminated water, breeding grounds for mosquitoes, heightened anxiety and conditions that allow preventable diseases to spread.
Unless governments act with urgency and citizens heed public health advice, the experts warned, Nigeria’s next tragedy may not be measured by the height of the floodwaters, but by the lives lost after the flood is gone.
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