On 2 June 2023, the Ministry of Health of the United Republic of Tanzania declared the end of its first documented outbreak of Marburg virus disease (MVD). Between 21 March and 31 May, a total of nine cases (eight laboratory-confirmed and one probable) were reported. All cases were reported from Bukoba district, Kagera region. A total of six deaths (case fatality ratio 67%) were reported during the outbreak.
In accordance with WHO recommendations, the declaration was made 42 days (twice the maximum incubation period for Marburg virus infection) after the last possible exposure to an MVD probable or confirmed case.
WHO encourages countries to maintain most response activities for three months after the outbreak ends. This is to make sure that if the disease re-emerges, health authorities would be able to detect it immediately, prevent the disease from spreading again, and ultimately save lives.
Description of the situation
On 21 March 2023, the Ministry of Health (MoH) of the United Republic of Tanzania officially declared the first MVD outbreak in the country. Between 21 March and 31 May, a total of nine cases, including eight laboratory-confirmed cases and one probable (the index case), were reported (Figure 1). The last confirmed case was reported on 11 April 2023 and the date of sample collection of the second negative PCR test was on 19 April 2023. All cases were reported from Bukoba district, Kagera region, in the north of the country.
Among the confirmed cases, three have recovered, and a total of six deaths (CFR 67%) have been reported, of which five were confirmed and one was a probable case.
Cases ranged in age from 1 to 59 years old (median 35 years old), with males being the most affected (n= 6; 67%). Six cases were close relatives of the index case, and two were healthcare workers who provided medical care to the patients.
On 2 June 2023, the MoH of the United Republic of Tanzania declared the end of the MVD outbreak. This declaration was made 42 days (twice the maximum incubation period for Marburg virus infection) after the last possible exposure to MVD probable or confirmed case.
Figure 1: Distribution of MVD cases (confirmed and probable) by date of symptom onset in the United Republic of Tanzania, as of 31 May 2023.
Figure 2: Map of district reporting MVD confirmed and probable cases in the United Republic of Tanzania, as of 31 May 2023.
Epidemiology of Marburg virus disease
Marburg virus spreads between people via direct contact through broken skin or mucous membranes with the blood, secretions, organs, or other body fluids of infected people and with surfaces and materials such as bedding, and clothing contaminated with these fluids. Healthcare workers have previously been infected while treating patients with suspected or confirmed MVD. Burial ceremonies involving direct contact with the body of the deceased can also contribute to the transmission of the Marburg virus.
The incubation period varies from 2 to 21 days. Illness caused by the Marburg virus begins abruptly, with high fever, severe headache, and severe malaise. Severe haemorrhagic manifestations may appear between five and seven days from symptom onset. However, not all cases have haemorrhagic signs, and fatal cases usually have some form of bleeding, often from multiple areas.
Early supportive care – rehydration with oral or intravenous fluids – and treatment of specific symptoms and co-infections can improve survival. A range of potential treatments are being evaluated, including blood products, immune therapies, and drug therapies.
This was the first documented outbreak of MVD reported in the United Republic of Tanzania. There is an ongoing outbreak of MVD in Equatorial Guinea (for more information, please see the Disease outbreak news published on 8 May 2023 in Equatorial Guinea and the United Republic of Tanzania). Other MVD outbreaks have been previously reported in Ghana (2022), Guinea (2021), Uganda (2017, 2014, 2012, 2007), Angola (2004-2005), the Democratic Republic of the Congo (2000 and 1998), Kenya (1990, 1987, 1980) and South Africa (1975).
Public health response
The MoH, together with WHO and other partners, initiated response measures to control the outbreak and prevent further spread to other regions in the country and neighboring countries. Regular coordination meetings were held to coordinate responses.
Active case search and alert management were implemented, with a total of 243 alerts received as of 30 May, of which 62 MVD suspected cases were detected, and samples were sent for laboratory confirmation. The eight laboratory-confirmed cases were identified, and the remaining samples tested negative.
A total of 212 contacts were identified and monitored with 210 having completed their 21-day follow-up period with no symptoms. Of the remaining two contacts, one developed symptoms and subsequently tested positive for MVD while the other died due to other causes.
The three recovered cases were provided with care and, together with their relatives, received mental health and psychosocial support services (MHPSS) through the survivor programme.
WHO risk assessment
On 2 June 2023, the Ministry of Health of Tanzania declared the end of the MVD outbreak that affected Bukoba district in Kagera region. This was the first documented MVD outbreak in the country.
MVD is an epidemic-prone disease associated with high case fatality ratios (CFR 24-90%). MVD is caused by the same family (Filoviridae) as Ebola virus disease (EVD) and is clinically similar. In the early course of the disease, clinical diagnosis of MVD is difficult to distinguish from other tropical febrile illnesses because of the similarities in the clinical symptoms. Other viral hemorrhagic fevers need to be excluded, particularly Ebola diseases, as well as malaria, typhoid fever, and dengue. Epidemiologic features can help differentiate between diseases (i.e., exposure to bats, caves, or mining).
Marburg virus has been isolated from fruit bats (Roussettus aegyptiacus) that are present in Tanzania and countries neighboring the affected Kagera region, therefore the same bat species may carry the virus in this region.
WHO advice
WHO encourages countries to maintain most response activities for three months after the outbreak is declared over. This is to make sure that if the disease re-emerges, health authorities would be able to detect it immediately, prevent the disease from spreading again, and ultimately save lives.
WHO advises the following risk reduction measures as an effective way to reduce MVD transmission:
Reducing the risk of bat-to-human transmission arising from prolonged exposure to mines or caves inhabited by fruit bat colonies. During work or research activities or tourist visits in mines or caves inhabited by fruit bat colonies, people should wear gloves and other appropriate protective clothing (including masks). During outbreaks, all animal products (blood and meat) should be thoroughly cooked before consumption.
Health facilities should ensure infection, prevention and control measure (IPC) programmes are in place including screening for cases of MVD, training of health workers on IPC practices, safe injection practices, environmental cleaning and disinfection protocols are in place, decontamination of reusable medical devices and safe waste management.
Health workers caring for patients with confirmed or suspected MVD should apply transmission-based precautions in addition to standard precautions, including appropriate use of personal protective equipment (PPE) and hand hygiene according to the WHO 5 moments to avoid contact with patients' blood and other body fluids and with contaminated surfaces and objects.
Surveillance activities should be strengthened to ensure early detection of any future cases.
Raising community awareness of the risk factors for Marburg infection and the protective measures that individuals can take to reduce human exposure to the virus are key to reducing human infections and deaths.
WHO advises against any other international travel and/or trade measures in the United Republic of Tanzania.
About WHO
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