By Adam Mustapha, PhD
Floods are natural disasters that occur globally, destroying lives and property, especially in developing countries like ours. As a natural disaster, it is caused by climate changes and human activities which distort the balance of environment, hosts and pathogens. Factors such as high sea level rise, urbanization, destruction of river banks, and deforestation increase the risk of flood disasters.
Flood results in the disturbance of the epidemiological triangle; environment, host and infectious agent, and as such, it could result in the emergence of new agents or re-emergence of infectious agents that previously existed. Therefore, the potential outbreak of infectious diseases is a matter of great concern, and urgent intervention is needed to break the chains of transmission.
Flood is known to increase the global burden of various infectious diseases, mortality, social and economic disruptions and displacement of people, which can result in both physical and psychological trauma. Of great concern is how flood causes the outbreaks of infectious diseases, as germs can easily be transported and contaminate drinking water sources, which will provide a conducive environment for the completion of the vector life cycle.
Like other developing countries, flooding has become an annual event in Nigeria, and many towns and cities are vulnerable and susceptible to it. This year, the Nigerian meteorological agency (NiMet) warned some states that they were at high risk of flooding in its yearly prediction of rainfall. Therefore, it was unsurprising that flooding hit many such states, states like Jigawa and Yobe have significantly been hit. In contrast, others such as Borno, Adamawa, Gombe, Kebbi, Kano, Kaduna, Lagos, Kogi, Niger, Delta, Rivers, Zamfara, Taraba, Ogun, Osun, Ondo, some parts of Ekiti, Edo and FCT are affected from moderately to low levels.
Flooding can cause waterborne diseases such as cholera, non-specific diarrhoea, typhoid and viral diarrhoea caused by Rotavirus. These diseases are known to peak after flooding as the pathogens such as bacteria, viruses, and parasites can be transported. In addition, the crowded nature of displacement camps can potentially result in and aggravate the outbreak of respiratory diseases.
The crowded nature of displacement camps can potentially result in the outbreak of respiratory diseases of different etiological agents. Wastewater is a breeding ground and carrier of infectious diseases. For instance, wastewater has the potential of spreading viruses, as they are known to be good-chance takers of a flood, which take days after flooding to meet their incubation cycle. Viral diarrheal diseases, such as hepatitis A and E, vector-borne viral diseases such as Yellow fever, and many others are also some diseases that could potentially spread after the flood.
The genome of some viruses, such as SARS-CoV-2, are known to be detected in community wastewater and this call for concern as it can be disseminated during a flood. Another agent to worry about due to flood is Naegleria fowleri, a brain-eating amoeba causing primary amoebic meningoencephalitis (PAM). As water level and temperature rise, such a situation could fuel the growth of the agent. Environmental contribution to the development of infectious diseases is a significant public health concern that should not be ignored. Antibiotic-resistant bacteria and antibiotic-resistant genes are quickly disseminated in environmental wastewater, which could be further transported into the water system, which calls for concern.
Furthermore, the vector-borne disease can occur as a result of a flood because the development cycles of vectors are provided. For instance, mosquito-borne diseases such as malaria and West-Nile fever tend to increase after floods. Rodent-borne diseases also expand during flooding because the flood increases contact between rodents and humans, resulting in outbreaks of such diseases. Common rodent-borne infectious agents due to flooding include Leptospirosis, Hantavirus pulmonary syndrome, Hemorrhagic fever with renal syndrome etc.
Health interventions
First, public health measures are essential in preventing infectious diseases due to floods. Therefore, preventive measures should be taken before, during and after the flooding.
Second, the provision of crucial intervention. The critical intervention is an active early warning system that can alert governments to prepare for possible outbreaks and send signals for evacuation of people at risk.
Third, the activation of rapid emergency response is also a necessity. This includes the provision of basic materials and health care services.
Fourth, after the flood, the activation of an effective surveillance method is mandatory for the early detection of an outbreak.
The key intervention is active early warning systems which can alert governments to prepare for possible outbreaks and send signals for evacuation of people at risk. At this stage, all stakeholders and the public must act on time. However, compliance is low due to a lack of an alert system or people refusing to abide by the warning system. Furthermore, risk assessment is needed to ensure that no basic amenities are disrupted due to floods.
Moreover, there is a need for vector control after the flood to break the chains of transmission. There is a need for collaboration among all public health stakeholders. Public enlightenment and outreaches are equally essential intervention measures.
Finally, provisions of clean water, sanitation and hygiene after the flooding to prevent infectious disease outbreaks are also very significant.
Adam Mustapha, PhD, is a clinical and medical microbiologist. He wrote from the Department of Microbiology, University of Maiduguri, via adadmustapha@unimaid.edu.ng.