Situation at a glance

Since the first Disease Outbreak News on this event was published on 25 February 2023, eight additional laboratory-confirmed cases of Marburg virus disease (MVD) have been reported in Equatorial Guinea. This brings the total to nine laboratory-confirmed cases and 20 probable cases since the declaration of the outbreak in February 2023. There are seven deaths among the laboratory confirmed, and all probable cases are dead. Of the eight new confirmed cases, two were reported from the province of Kié-Ntem, four from the Litoral,  and two from Centre- Sur provinces. The areas reporting cases are about 150 kilometers apart, suggesting wider transmission of the virus.

WHO has deployed experts to support national response efforts and strengthen community engagement in the response.

MVD is a highly virulent disease that causes haemorrhagic fever, and is among the viral haemorrhagic fevers that require assessment under the International Health Regulations.

WHO assesses the risk posed by the outbreak as very high at the national level, moderate at the regional level, and low at the global level.

Description of the situation

On 7 February 2023, the Ministry of Health and Social Welfare of Equatorial Guinea reported at least eight suspected MVD deaths that occurred between 7 January and 7 February 2023, in two villages located in the district of Nsok Nsomo, in the eastern province of Kié-Ntem, Río Muni Region.

On 12 February 2023, eight blood samples were collected from contacts and sent to the Institute Pasteur in Dakar, Senegal, where one of these samples was confirmed positive for Marburg virus by real-time polymerase chain reaction (RT-PCR). This case presented with fever, vomiting, blood-stained diarrhoea, convulsions, and died on 10 February 2023 in a hospital. The case also had epidemiological links to four deceased suspected cases from one of the villages in Nsok-Nsomo district.

On 13 March 2023, samples from two additional individuals from Kié-Ntem province tested positive for MVD by RT-PCR performed at a mobile laboratory at the Regional Hospital of Ebibeyin. Another sample, obtained from a resident of Litoral province in the western part of the country, epidemiologically linked to a confirmed case in Kié-Ntem, tested positive for MVD on 15 March 2023 following RT-PCR performed by the same laboratory. The two provinces (Kié-Ntem and Litoral) are located in different parts of the country, about 150 kilometers apart. On 18 and 20 March three additional laboratory confirmed positive cases were reported from Litoral province. On 20 March two more laboratory confirmed cases were reported from Centre Sur province. The wide geographic distribution of cases and uncertain epidemiological links in Centre Sur province suggests the potential for undetected community spread of the virus.

Overall, since the beginning of the outbreak and as of 21 March, a cumulative number of nine confirmed and 20 probable cases have been recorded in Equatorial Guinea.

Epidemiology of Marburg virus disease

Marburg virus and the closely related Ravn virus are the causative agents of Marburg virus disease, which has a case-fatality ratio of up to 88%. Marburg virus disease was initially detected in 1967 after simultaneous outbreaks in Marburg and Frankfurt in Germany, and in Belgrade, Serbia. Rousettus aegyptiacus fruit bats are considered natural hosts for Marburg virus, from which the virus is then transmitted to people.

Marburg spreads between people via direct contact through broken skin or mucous membranes with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials such as bedding, clothing contaminated with these fluids. Healthcare workers have previously been infected while treating patients with suspected or confirmed MVD. Burial ceremonies that involve direct contact with the body of the deceased can also contribute to the transmission of Marburg.

The incubation period varies from two to 21 days. Illness caused by Marburg virus begins abruptly, with high fever, severe headache, and severe malaise. Severe watery diarrhoea, abdominal pain and cramping, nausea, and vomiting can begin on the third day. Severe haemorrhagic manifestations may appear between five and seven days from symptom onset, and fatal cases usually have some form of bleeding, often from multiple areas. In fatal cases, death occurs most often between eight and nine days after symptom onset, usually preceded by severe blood loss and shock.

In the early course of the disease, the clinical diagnosis of MVD is difficult to distinguish from many other tropical febrile illnesses due to the similarities in the clinical symptoms. Other viral haemorrhagic fevers need to be excluded, including Ebola virus disease, as well as malaria, typhoid fever, leptospirosis, rickettsial infections, and plague.

Laboratory confirmation is primarily made by RT-PCR. Other tests can be used such as antibody-capture enzyme-linked immunosorbent assay (ELISA), antigen-capture detection tests, serum neutralization test, electron microscopy, and virus isolation by cell culture.

Although no vaccines or antiviral treatments are approved to treat the virus, supportive care – rehydration with oral or intravenous fluids – and treatment of specific symptoms improve survival. A range of potential treatments are being evaluated, including blood products, immune therapies, and drug therapies.

This is the first time that Equatorial Guinea has reported an outbreak of MVD. The most recently reported outbreak of MVD was in Ghana in 2022 (where there were three confirmed cases). Other MVD outbreaks have been previously reported in Guinea (2021), Uganda (2017, 2014, 2012, 2007), Angola (2004-2005), the Democratic Republic of the Congo (1998 and 2000), Kenya (1990, 1987, 1980) and South Africa (1975).

Public health response

• In-depth epidemiological investigations are ongoing to determine the source of the outbreak.
• National teams have been deployed to the affected districts for active case finding, contact tracing, and clinical management of suspected cases.
• WHO has deployed experts in epidemiology, case management, infection prevention and control (IPC), laboratory, and risk communication to support national response efforts and ensure community engagement.
• WHO has shipped materials for sample collection and analysis, and viral haemorrhagic fever kits including personal protective equipment for 500 health workers.
• WHO is supporting the training of national responders in surveillance, case management, IPC, safe and dignified burial (SDB), and risk communication and community engagement (RCCE).
• The Government has activated the public health emergency operation center (PHEOC) at Ebibeyin and now in Bata under the leadership of the Minister of Health and the District Chief Medical Officer.
• WHO is supporting ongoing community engagement activities to create awareness, share prevention information, and encourage reporting of alerts.
• Alert systems have been established with the availability of a hotline.

WHO risk assessment

Equatorial Guinea is facing an outbreak of MVD for the first time while the country's capacity to manage the outbreak needs to be strengthened.

In addition to the one confirmed case reported in the Disease Outbreak News of 25 February, eight more individuals have tested positive for MVD, indicating that exposure to the virus may be more widespread.

All three affected provinces have international borders with Cameroon and Gabon. Cross-border population movements are frequent, and the borders are very porous. Although no MVD cases have been reported outside Equatorial Guinea the risk of international spread cannot be ruled out.

Considering the above-described situation, and based on newly available information since the last update, the geographical spread of the outbreak in Equatorial Guinea and the uncertain epidemiological links for some of the confirmed cases, the risk assessment is currently being reviewed, however, it is considered very high at the national level, high at sub-regional level, moderate at the regional level and low at the global level.

WHO advice

Marburg virus disease outbreak control relies on using a range of interventions, such as prompt isolation and case management; surveillance including active case search, case investigation and contact tracing; an optimal laboratory service; infection prevention and control, including prompt safe and dignified burial; and social mobilization – community engagement is key to successfully controlling MVD outbreaks. Raising awareness of risk factors for Marburg infection and protective measures that individuals can take is an effective way to reduce human transmission.

Healthcare workers caring for patients with confirmed or suspected MVD should apply additional IPC measures beyond standard precautions to avoid contact with patients’ blood and body fluids and with contaminated surfaces and objects.

WHO recommends that male survivors of MVD practice safer sex and hygiene for 12 months from onset of symptoms, or until their semen twice tests negative for the Marburg virus. Contact with body fluids should be avoided and washing with soap and water is recommended. WHO does not recommend isolation of male or female convalescent patients whose blood has tested negative for the Marburg virus.

Based on the available information and current risk assessment, WHO advises against any travel and trade restrictions in Equatorial Guinea.