The floods that have inundated large parts of Pakistan in recent weeks have killed about 1,500 people and displaced tens of millions, but the final death toll is likely to be much higher. From disease to healthcare disruption, flood events affect people’s health through various direct and indirect ways. Such events are also expected to increase in frequency as a result of climate change and rising sea levels. So what makes floodwaters so deadly, and is there anything countries can do to reduce losses?
Floods can cause widespread damage to crops and livestock, affecting the quantity and quality of food available.
1. Drowning and acute injury
Floods make up 40% of all natural disasters worldwide and are responsible for about half of all associated deaths. Most of these deaths are from drowning – particularly from people being trapped in their cars while trying to drive through torrential rain. Fatalities can also occur if people are exposed to fast-moving water, as a result of excessive stress, hypothermia, or electrocution, or as a result of collisions with objects similarly trapped in floodwaters, including fallen trees. Some of these infections may not kill immediately, but in the days or weeks after the event, such as infection of wounds with bacteria in floodwaters.
Carbon monoxide poisoning is surprisingly common, as people use pumps, generators, and pressure washers to disinfect or dry out buildings without adequate ventilation.
Access to clean water is often a major problem in the wake of severe floods. Floods can cause sewage to overflow, contaminate drinking water and increase the risk of gastro-intestinal diseases, while poor hygiene and overcrowding of shelters can exacerbate the situation.
Recent floods in Bangladesh have resulted in large outbreaks of bacterial gastroenteritis, particularly cholera and the pathogenic Escherichia coli – with cholera outbreaks occurring approximately eight days after the initial floods. Rapid distribution of the oral cholera vaccine can help mitigate this risk, although it is difficult to deliver to flood-affected communities.
Other diseases associated with flood events include typhoid fever, hepatitis A and E, rotavirus, and norovirus. Submersion or inhalation in floodwaters can also lead to lower respiratory infections such as pneumonia, as well as skin or eye diseases, or leptospirosis (Will’s disease), which is spread through contact with rodent urine.
As flood waters recede, pools of stagnant water can become a breeding ground for mosquitoes, increasing the risk of mosquito-borne diseases such as dengue and malaria. Already, there has been an increase in dengue cases in Pakistan, with at least 3,830 cases and 9 deaths reported by health officials in Sindh province as of September 15, 2022. Health officials have also reported an increase in malaria, diarrhea and skin diseases after a flood.
3. Poisonous creatures
Humans are not the only ones made homeless by floods. Wild animals, including snakes and spiders, may take refuge inside homes, warehouses, and other buildings, especially if they have been damaged. Rapid antivenom treatment is essential for those bitten by venomous snakes, but flooding can also hinder access to treatment.
As of August 30, 134 people in Pakistan were reported to have suffered snakebites as a result of the floods, including a woman in northwestern Khyber Pakhtunkhwa province who died after failing to obtain urgent medical care. In addition to fatalities, venomous snakebites and spider stings can cause permanent disabilities.
4. Disabled health care
When Cyclone Anna hit Malawi in late January 2022, it caused widespread flooding in some areas. This has resulted in severe damage to health infrastructure, including clinics, health records, cold chain equipment, medicines and medical supplies. Many individuals also lost their regular medication in the floods.
One consequence of this disorder is the deteriorating health of people with chronic diseases such as diabetes or cardiovascular disease, with associated increased mortality. For example, following flood events in Florida during the 2004 hurricane season, there was an increase in heart attacks, and doctors reported a deterioration in patients’ blood pressure control.
Flooding can also hamper the delivery of vaccines, particularly in rural areas where people have to travel to reach clinics.
Floods can cause widespread damage to crops and livestock, affecting the quantity and quality of food available. For example, in parts of South Sudan, floods over the past three years have resulted in many people not being able to cultivate their land. Some have also lost livestock to diseases caused by animals grazing in flooded fields and many have resorted to foraging for wild foods such as water lilies. Undernutrition or malnutrition remains a major threat to health.
6. Psychological trauma
Although it may not be fatal, the emotional impact of losing one’s home, possessions, or livelihood lingers long after the flood waters recede. There are also economic stresses associated with rebuilding, adding to the psychological toll. Mental health problems in the aftermath of floods are often overlooked and not as well studied as the direct health effects of floods.
According to research conducted in the UK following large-scale flooding during the winter of 2013/2014, the prevalence of depression, anxiety and PTSD remained high for at least two years after flood exposure. “Our research suggests that support to deal with the extended damage to homes, sanitation, and facilities caused by flooding may be necessary to reduce mental health risks,” the authors wrote.
In Bangladesh, interviews with flood survivors indicated that about 57.5% of them experienced suicidal thoughts, while 6% and 2% planned or attempted suicide, respectively. Suffering from depression, anxiety, post-traumatic stress disorder, and experiencing financial problems or economic hardship were among the main risk factors identified.