Disease Outbreak News: Cholera – Malawi (27 April 2022)

Outbreak at a glance

The Ministry of Health declared a cholera outbreak in Malawi on 3 March 2022, following laboratory confirmation of a case in in the country. A second case was detected in on 7 March. As of 26 April, 78 cholera cases and four deaths have been reported, of which 97% (76 cases) have been reported from Nsanje district. Several response measures have been implemented including delivery of cholera kits, mapping of hotspot districts.

Description of the outbreak

On 3 March 2022, the Ministry of Health Malawi declared a cholera outbreak in the country, following confirmation of a case in a 57-year-old male, from Machinga district, in Southern Malawi. On 28 February, the case developed watery diarrhoea and visited Machinga hospital where cholera was confirmed on 2 March. Samples from the patient tested positive by culture and Vibrio cholerae O1, serotype Inaba was isolated. The case had a history of travel to two cities – Blantyre and Machinga — prior to being admitted to the district hospital. Although an epidemiological investigation was carried out, the source of the infection was not identified.

On 7 March 2022, a second case was identified in a 11-year-old boy at a local health centre from Nsanje district, Malawi. The case was displaced to Mozambique following floods caused by the tropical storm Ana and cyclone Gombe and returned to Malawi while symptomatic.

As of 26 April 2022, a total of 78 cholera cases with four deaths (case fatality ratio: 5.1%) have been reported from Nsanje (76 cases; four deaths) and Machinga (2 cases) districts (Figures 1 and 2). Of the 78 cases, 13 have been confirmed by culture, and 20 tested positive by rapid diagnostic test (RDT). The age of the cases range between 2 and 57 years, with the 5 to 14 years age group being the most affected.

The Southern region of Malawi was severely affected by the tropical storm Ana and cyclone Gombe that caused torrential rains and floods between late January and February 2022. The displaced populations remained with no access to safe drinking water and sanitation facilities and thus, at risk of widespread disease outbreaks including cholera.

Epidemiology of cholera

Cholera is an acute enteric infection caused by ingesting the bacteria Vibrio cholerae present in contaminated water or food. It is mainly linked to insufficient access to safe drinking water and inadequate sanitation. It is an extremely virulent disease that can cause severe acute watery diarrhoea resulting in high morbidity and mortality, and can spread rapidly, depending on the frequency of exposure, the exposed population and the setting. Cholera affects both children and adults and can be fatal if untreated.

The incubation period is between 12 hours and 5 days after ingestion of contaminated food or water. Most 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, the majority have mild or moderate symptoms, while a minority develop acute watery diarrhoea with severe dehydration. Cholera is an easily treatable disease. Most people can be treated successfully through prompt administration of oral rehydration solution (ORS).

Cholera can be endemic or epidemic. A cholera-endemic area is an area where confirmed cholera cases were detected during the last 3 years with evidence of local transmission (cases are not imported from elsewhere). A cholera epidemic can occur in both endemic countries and in non-endemic countries.

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. Uninfected dead bodies have never been reported as the source of epidemics.

A multifaceted approach including a combination of surveillance, water, sanitation and hygiene, social mobilization, treatment, and oral cholera vaccines is essential to control cholera outbreaks and to reduce deaths.

Public health response

WHO, in coordination with partners, is supporting the implementation of the National Cholera Response Plan in Malawi.

Other specific actions undertaken include:

• National and district level emergency operation centres (EOCs) were activated and currently coordinating the response in collaboration with other health sectors and partners.

• Initial mapping of the high risk/ hotspot districts was conducted in late February 2022, after the landfall of tropical storm, and an update was conducted on 25 March 2022.

• The Ministry of Health and WHO jointly completed field supervision including risk and needs assessments. A comprehensive report is being prepared.

• Four data managers and three public health officers were engaged and deployed to the affected districts for data management.

• Cholera preparedness training was conducted from 21 to 22 April 2022 in Nsanje district.

• WHO has provided cholera kits and other supplies to the affected districts.

• A request for an oral cholera vaccine (OCV) submitted to the International Coordination Group (ICG) for 3.9 million doses of vaccines targeting eight high risk districts was approved. The country has received more than 1.9 million doses of OCV for the first round of the campaign planned for early May 2022.

• Supplies for case management and laboratory confirmation of cholera are pre-positioned in health facilities and the district laboratory. Case management has been strengthened through the establishment of treatment structures and the provision of equipment. Two cholera treatment centres have been established in Nsanje district.

• The collection and analysis of stool samples for confirmation at the district public health laboratory continues. A total of 13 samples were confirmed by laboratory analysis (culture) as of 26 April 2022.

• Efforts to collaborate with the Mozambique team are underway through the regional coordination in the East, Central and South Africa.

WHO risk assessment

Cholera is endemic in Malawi with seasonal outbreaks being reported from 1998 to 2020. The Southern region, which shares border with Mozambique, remains the hotspot of the recurrent cholera outbreaks. The detection of cholera cases is concerning as Malawi has low population immunity in the districts reporting confirmed cases.

The main factors attributed to the initiation and ongoing spread of the cholera epidemics in the two affected districts include:

• Tropical storm and floods

• Inadequate hygiene and sanitation

• Limited access to safe drinking water and personal hygiene practices

• Open defecation

• Delay in seeking care

Other identified challenges from Nsanje and neighbouring at-risk districts (Balaka and Chikwawa) include poor capacity for sample collection, transportation, and diagnosis in the affected areas mainly due to the difficult access following floods.

Additionally, Malawi shares international borders with Mozambique, and there is frequent and substantial cross-border population movement, including people displaced following the floods caused by the tropical cyclone. This poses a risk of cross-border transmission of cholera.

Close monitoring of the situation with active cross-border coordination and information sharing remains crucial.

WHO advice

Prevention and control: WHO recommends improving access to clean water and sanitation, good waste management, food safety practices and hygienic practices to prevent the transmission of cholera. OCV should be used in combination with improvements in water and sanitation to control cholera outbreaks and for prevention in areas known to be at-high risk for cholera.

Surveillance: Strengthening surveillance, particularly at the community level, is advised. There is a need to ensure that countries are ready to quickly detect and respond to this cholera outbreak to reduce the risk of spread to new areas. As the outbreak is occurring in border areas where there is significant cross border movement, WHO encourages the respective countries to ensure cooperation and regular information sharing.

Case management: Appropriate case management, including improving access to care, should be implemented in outbreak-affected areas to reduce mortality.

International travel and Trade: WHO does not recommend any restrictions on travel and trade to and from Malawi.

Source: World Health Organization