As of 11 January 2022, 385 suspected cases of Hepatitis E virus (HEV) have been reported, of which, 12 are confirmed and two associated deaths (case fatality ratio (CFR): 0.5%) have been reported in six villages in Lai district, Tandjile region, Chad. Health authorities began an investigation on 1 October 2021 for a cluster of 25 suspected HEV cases presenting with jaundice, fever, and epigastric pain. Of the tested samples at the Ndjamena General Hospital, 65% (13/20)  were positive for HEV using rapid diagnostic tests. The same batch of 20 samples was referred to the Centre Pasteur in Yaoundé, Cameroon, a WHO collaborating centre for confirmation and 12 tested positive for HEV by enzyme-linked immunosorbent assay. The results for blood samples from a further 29 of the suspected cases  remain pending.

Of the 385 reported cases, more than half were male (n=215; 57%). Cases aged less than 10 years (n=90; 23.4%) and 21-30 years (n=89; 23.1%) accounted for the largest proportion of cases.

Heavy rain in Chad since June 2021 have greatly impacted the Tandjile region and by October 2021, approximately 161 000 people were affected. Floodwaters caused substantial infrastructural damage in a setting that has pre-existing water, sanitation and hygiene (WASH) challenges such as a poor access to safe drinking water and high rates of open defecation.

The last known outbreak of HEV in Chad began in August 2016 and lasted for 17 months before the Ministry of Health declared the end of the outbreak in February 2018. A total of 1874 suspected HEV cases and 23 associated deaths were reported. The area affected in this outbreak was located in the Salamat region, just over 700 km north east of the current outbreak. 

Public health response

• Coordination meetings have been organised for the district management team, Ministry of Health team, and partners.
• Case management is being coordinated at a provincial and district-level.
• Field investigations have been conducted in the affected areas and samples (both human and environmental) were collected and analysed.
• Active surveillance is ongoing within the communities.
• Water, sanitation and hygiene (WASH) activities are ongoing including enumeration of boreholes in all affected villages and provision of water and sanitation to the affected areas.
• Community risk communication activities are ongoing.

WHO risk assessment

Suspected HEV cases have been detected in Chad after nearly four years without any reported cases. Heavy rains causing flooding have created favourable conditions for HEV transmission, including a large amount of displaced people living in precarious situations where clean drinking water, sanitation, hygiene, and health services are limited.

The main risks of spread at the national level are 1) poor sanitation and hygiene practices especially in areas affected by floods; 2) high rates of open defecation; 3) lack of access to safe drinking water; and 4) presence of large internally displaced population.

At a regional level, the risk of HEV transmission is currently low. However, the risk may be affected by the increased number of displaced persons in Tandjile region and from other southern regions of the country, some of which share a border with Cameroon and the Central African Republic. HEV outbreaks are currently occurring in South Sudan and Sudan, however no epidemiological links have been established with the outbreak in Chad. During the last documented outbreak in Chad which ended in 2018, genomic sequencing of isolates from HEV cases reported in South Sudan showed HEV genotype 1, sub-genotype 1e, that was closely related to strains isolated in Chad and Uganda. 

WHO advice

Hepatitis E is a liver disease caused by the HEV. Hepatitis E is found worldwide and is common in countries with limited access to essential water, sanitation, hygiene, and health services, or in areas with humanitarian emergencies.

HEV is transmitted mainly by the faecal-oral route, primarily through contaminated water. The infection is usually self-limiting and resolves within 2–6 weeks. Occasionally a serious disease known as fulminant hepatitis (acute liver failure) develops, which can be fatal. Fulminant hepatitis is more common when hepatitis E occurs during pregnancy, especially in the second and third trimester, putting pregnant women at increased risk of acute liver failure, foetal loss, and mortality. The case-fatality ratio can be as high as 20-25% in the last trimester of pregnancy.

There is no specific treatment capable of altering the course of acute hepatitis E other than general management of acute liver failure as needed, and supportive care. As the disease is usually self-limiting, hospitalization is generally not required.

Prevention is crucial against this disease. At the population level, the most important interventions to reduce the transmission of HEV are provision of safe drinking water, and provision of adequate water and sanitation hygiene. At the individual level, risk of infection can be reduced by maintaining hygienic practices such as washing hands with clean water and soap - especially before handling food, avoiding consumption of water and/or ice of unknown purity, and following other WHO hygiene practices for food safety. Coverage of latrines and drinking water sources, along with community engagement should be increased in conjunction with other sanitation interventions in an aim to prevent open defecation and to ensure hand hygiene.

Health promotion and prevention activities, as well as ensuring early, appropriate, and equitable health care services to combat HEV epidemics, can help improve public health outcomes, especially in resource-limited settings.

As the incubation period for HEV ranges from 2-10 weeks, cases may continue to occur up to the tenth week (maximum incubation period) even after measures to ensure safe WASH promotion have been adopted.

It remains important that interventions continue to target vulnerable populations by establishing or strengthening antenatal diagnosis for pregnant women with symptoms, strengthening national capacities for diagnosis and clinical case management, and cross-border collaboration with neighboring countries.

A hepatitis E vaccine has been developed for commercialization and licensed in China and Pakistan. While WHO does not recommend the introduction of the vaccine as part of national routine immunization programs, WHO recommends that national authorities may decide to use the vaccine in outbreak settings, including in populations at high risks, such as pregnant women. Vaccine use should therefore be considered to mitigate or prevent an outbreak of hepatitis E, as well as to reduce the effects of an outbreak in high-risk individuals.

WHO advises against the application of any travel or trade restrictions on Chad or any of the affected countries based on the currently available information.