Nigeria’s cholera outbreaks: why they happen and are so hard to control

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On 9 June 2024 the Lagos State government declared a cholera outbreak. Three days later, it announced that 324 suspected cases had been reported in the state, including 15 people who died and 40 who were discharged after treatment. The Nigeria Centre for Disease Control and Prevention reported that as of 11 June, 1,141 suspected cholera cases had been recorded across 30 states in Nigeria since 1 January 2024. There were 65 confirmed cases with 30 deaths reported from 96 local governments in 30 out of the 36 states. The Conversation Africa asked Stella Smith, a molecular epidemiologist, to explain the causes, spread, treatment and prevention of cholera.

What is cholera and how does it spread?

Cholera is a disease caused by eating food and drinking water contaminated with the bacterium Vibrio cholerae. Its symptoms are severe diarrhoea (“rice water stool”), dehydration, weakness, muscle cramps, fever, vomiting, low blood pressure and thirst.

It can be spread when people do not wash their hands with soap and water after defecating and then cook or serve food with unwashed hands. Cholera also spreads when people eat food without washing their hands before and after eating. If cooked food is not covered, it may get contaminated from flies that carry the bacteria. Cholera also spreads when raw fruits and vegetables are not thoroughly washed in clean running water before being eaten. Eating raw seafoods contaminated with cholera bacterium is another way people get infected.

Not filtering and boiling unsafe water before drinking, or drinking sachet water that is not treated, can cause cholera. It also spreads when an infected person defecates outside and contaminated faeces are washed into the water system that people drink from. Even a pit latrine should be at least 30 metres away from a drinking water source.

Also contributing to the spread of cholera are:

• indiscriminate dumping of refuse and irregular disposal of sewage, enabling flies to carry the bacteria to water or food

• blocked drains and leaking water pipes

• overcrowded conditions such as internally displaced persons' camps, refugees and prisons with no access to safe water.

A food handler who prepares drinks such as tigernut or zobo with contaminated water can spread cholera too. The Lagos State government mentioned these local drinks as suspected sources of the latest outbreak.

How deadly is it?

When a person is infected with cholera, their small intestine releases a toxin which causes the body to secrete enormous amount of water. This leads to diarrhoea and a rapid loss of fluids and electrolytes. The later a patient gets treatment, when severe dehydration and shock have set in, the higher the risk of death. Even then, cholera kills in a small percentage of cases.

Why is Nigeria prone to annual cholera outbreaks?

Cholera has been endemic in Nigeria since it first appeared in 1972. The 1991 outbreak was the most severe on record, resulting in 59,478 cases and 7,654 deaths, a case fatality rate of 12.9%.

The World Health Organization recommended benchmark case fatality rate is less than 1%. This rate is the number of deaths in the country as a percentage of the total confirmed cases (both alive and dead). Rates in Nigeria's outbreaks have mostly fluctuated between 1% and about 4%.

The 1991 rate was high due to very poor sanitation and hygiene strategies. Little or no surveillance was in place and there was no community engagement or education on the dangers of the disease.

Nigeria is prone to a variety of factors that lead to recurring cholera outbreaks. They include lack of access to potable (safe to drink) water. Safe water is needed to maintain good hygiene practices. Other factors are lack of continued surveillance even after the outbreak has ended; flooding; poverty (although currently cholera treatment is free in all government facilities); lack of health facilities; illiteracy; lack of infrastructure for water supply and waste disposal; and conflict, leading to overcrowded conditions for displaced people.

How can it be prevented?

Prevention depends on:

• access to clean water

• sanitation

• proper waste disposal

• personal hygiene

• food safety practices.

Community engagement and information campaigns on how to prevent cholera infection are important.

People can also take Oral Rehydrated Solution or homemade oral rehydration salts such as one litre of clean water with six teaspoons of sugar and half a teaspoon of salt. If symptoms persist within the day, report to the hospital quickly. Early reporting of cholera prevents its spread. Late reporting could lead to death.

There are oral cholera vaccines for use in high-risk areas. They are taken in two doses (one week to six weeks apart) and they provide protection for three years.

Nigeria currently is facing a shortage of these vaccines, making prevention and treatment challenging.

Stella Ifeanyi Smith does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

By Stella Ifeanyi Smith, Professor of Microbiology, Mountain Top University