Cholera Programme

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Researchers have estimated that every year, there are roughly 1.4 to 4.3 million cases, and 28 000 to 142 000 deaths per year worldwide due to cholera. The short incubation period of 2 hours to 5 days, is 1 factor that triggers the potentially explosive pattern of outbreaks.

Symptoms

Cholera is an extremely virulent disease. It affects both children and adults and can kill within hours.

About 80% of people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1-10 days after infection and are shed back into the environment, potentially infecting other people.

Among people who develop symptoms, 80% have mild or moderate symptoms, while around 20% develop acute watery diarrhoea with severe dehydration. This can lead to death if left untreated.

Vibrio cholerae strains

Two serogroups of V. cholerae – O1 and O139 – cause outbreaks. V. cholerae O1 causes the majority of outbreaks, while O139 – first identified in Bangladesh in 1992 – is confined to South-East Asia.

Non-O1 and non-O139 V. cholerae can cause mild diarrhoea but do not generate epidemics.

Recently, new variant strains have been detected in several parts of Africa. Observations suggest that these strains cause more severe cholera with higher case fatality rates. Careful epidemiological monitoring of circulating strains is recommended.

The main reservoirs of V. cholerae are people and aquatic sources such as brackish water and estuaries, often associated with algal blooms. Recent studies indicate that global warming creates a favourable environment for the bacteria.

Risk factors and disease burden

Cholera transmission is closely linked to inadequate environmental management. Typical at-risk areas include peri-urban slums, where basic infrastructure is not available, as well as camps for internally displaced persons or refugees, where minimum requirements of clean water and sanitation are not met.

The consequences of a humanitarian crisis – such as disruption of water and sanitation systems, or the displacement of populations to inadequate and overcrowded camps – can increase the risk of cholera transmission should the bacteria be present or introduced. Dead bodies have never been reported as the source of epidemics.

Cholera remains a global threat to public health and a key indicator of lack of social development.

Prevention and control

A multidisciplinary approach is key for reducing cholera outbreaks, controlling cholera in endemic areas and reducing deaths.

Water and sanitation interventions

The long-term solution for cholera control (which benefits all diseases spread by the fecal-oral route) lies in economic development and universal access to safe drinking water and adequate sanitation, which is key in preventing both epidemic and endemic cholera.

Actions targeting environmental conditions include:

• the development of piped water systems with water treatment facilities (chlorination);
• interventions at the household level (water filtration, water chemical or solar disinfection, safe water storage containers); and
• as well as the construction of systems for sewage disposal and latrines.

Most of those interventions require substantial long term investments and high maintenance costs which are difficult to fund and sustain by the least developed countries, where they are also most needed.

Treatment

Cholera is an easily treatable disease. Up to 80% of people can be treated successfully through prompt administration of oral rehydration salts. Very severely dehydrated patients require the administration of intravenous fluids. These patients also need appropriate antibiotics to diminish the duration of diarrhoea, reduce the volume of rehydration fluids needed, and shorten the duration of V. cholerae excretion. Mass administration of antibiotics is not recommended, as it has no effect on the spread of cholera and contributes to increasing antimicrobial resistance.

In order to ensure timely access to treatment, cholera treatment centres (CTCs) should be set up within the affected communities. With proper treatment, the case fatality rate should remain below 1%.

Surveillance

Under the International Health Regulations, notification of all cases of cholera is no longer mandatory. However, public health events involving cholera must always be assessed against the criteria provided in the Regulations to determine whether there is a need for official notification.

Local capacities for improving diagnosis, and for collecting, compiling and analysing data, need to be strengthened so that vulnerable populations living in high-risk areas can be identified in order to benefit from comprehensive control activities. Cholera surveillance should be part of an integrated disease surveillance system that includes feedback at the local level and information-sharing at the global level.

Social mobilisation

Health education campaigns, adapted to local culture and beliefs, should promote the adoption of appropriate hygiene practices such as hand-washing with soap, safe preparation and storage of food and breastfeeding.

Awareness campaigns during outbreaks also encourage people with symptoms to seek immediate health care. The campaigns should use modern communication channels (mobile phones, smartphones, social media, etc.) and adapted to local cultures. The use of qualitative methods of analysis, to help adapt messages to local culture and beliefs, is also encouraged.

Oral cholera vaccines

Currently there are 2 oral cholera vaccines (OCVs) (Dukoral® and Shanchol®). Both vaccines have been used in mass vaccination campaigns with WHO support. Their use has enabled evidence to be collected on the effectiveness and feasibility on implementation of oral cholera vaccination campaigns as a public health tool in protecting populations at high risk of cholera.

The objectives of AHO cholera vaccines are to:

• break the current cycle of low demand–low supply, significantly increasing global OCV production and availability;
• reduce the impact of cholera outbreaks; and
• strengthen the evidence base for periodic pre-emptive campaigns.

Impact on cholera burden or transmission was significant in all endemic, outbreak and emergency settings. Furthermore, contrary to earlier concerns, the communities readily accepted the vaccines and high vaccine coverage were reported. No serious adverse effects have been reported so far.

Travel and trade

Countries neighbouring cholera-affected areas are encouraged to strengthen disease surveillance and national preparedness to rapidly detect and respond to outbreaks should cholera spread across borders. Further, information should be provided to travellers and the community on the potential risks and symptoms of cholera, together with precautions to avoid cholera, and when and where to report cases.

AHO Programme of Action

AHO works to:

• support the design and implementation of global strategies to contribute to capacity development for cholera prevention and control globally;
• provide a forum for technical exchange, coordination, and cooperation on cholera-related activities to strengthen countries’ capacity to prevent and control cholera;
• support countries for the implementation of effective cholera control strategies and monitoring of progress;
• disseminate technical guidelines and operational manuals;
• support the development of a research agenda with emphasis on evaluating innovative approaches to cholera prevention and control in affected countries;
• increase the visibility of cholera as an important global public health problem through the dissemination of information about cholera prevention and control, and conducting advocacy and resource mobilisation activities to support cholera prevention and control at national, regional, and global levels.

Cholera remains a public health threat in Africa and is one of the key indicators of social development. While the disease no longer poses a threat to countries with minimum standards of hygiene, it remains a challenge to countries where access to safe drinking water and adequate sanitation cannot be guaranteed