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DISEASE OUTBREAK NEWS

Marburg virus disease - Equatorial Guinea and the United Republic of Tanzania

8 May 2023

Situation at a glance

Equatorial Guinea and the United Republic of Tanzania have been responding to separate outbreaks of Marburg virus disease (MVD) since early February and late March 2023, respectively.

In Equatorial Guinea, from 13 February to 1 May 2023, 17 laboratory-confirmed MVD cases and 23 probable cases have been reported. The last confirmed case was reported on 20 April. Among the laboratory-confirmed cases, there are 12 deaths (Case Fatality Ratio (CFR) 75%).For one confirmed case, the outcome is unknown. Among the confirmed cases, four have recovered. All of the probable cases are dead. The most affected district is Bata in Litoral province, with 11 laboratory-confirmed MVD cases reported.

In the United Republic of Tanzania, between 16 March to 30 April 2023, a cumulative total of nine cases including eight laboratory-confirmed cases and one probable case have been reported. The last confirmed case was reported on 11 April 2023. A total of six deaths (CFR 66.7%) have been reported, including one probable case and five among the confirmed cases. Among the confirmed cases, three have recovered. All cases have been reported from Bukoba district, Kagera region.

Health authorities in both countries have shown strong political commitment. In recent weeks they have further strengthened critical response functions, such as disease surveillance, including at points of entry; laboratory activities; clinical case management; infection prevention and control; risk communication and community engagement; and operations support and logistics with support of WHO and partners.

WHO continues to monitor the situation in these two countries closely and to support the responses.

For full DON, see https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON467

Description of the situation

Equatorial Guinea:

Since the declaration of the outbreak on 13 February 2023, a total of 17 laboratory-confirmed cases of MVD and 23 probable cases have been reported as of 1 May (Figure 1). Among laboratory-confirmed cases, 12 deaths were recorded (CFR 75%). For one confirmed case, the outcome of the illness is unknown. All probable cases are dead. Five districts (Bata, Ebebiyin, Evinayong, Nsok Nsomo and Nsork) in four of the country’s eight provinces (Centro Sur, Kié-Ntem, Litoral and Wele-Nzas) have reported confirmed or probable cases (Figure 2). The most affected district is Bata in Litoral province, with 11 laboratory-confirmed MVD cases reported.

Among the confirmed cases, four have recovered and five have been reported among healthcare workers, of whom two died.

Among the reported cases, many are linked within a social network/gathering or by geographic proximity, however, the earlier presence of cases and/or clusters across multiple districts without clear epidemiologic links may indicate undetected virus transmission.

There are currently no confirmed cases in the Marburg treatment centre following the most recent discharge of a patient on 26 April 2023. This brings the total of survivors to four since the outbreak was declared.

Among MVD laboratory-confirmed cases with age and sex information (n = 16), the majority occurred among females (10/16; 62.5%), while the most affected age group is 40-49 years (6/16; 37.5%), followed by the age groups 30-39 years (3/16; 18.8%), 10-19 years (2/16; 12.5%), and 0-9 years (2/16; 12.5%).

In the last 21 days (from 11 April to 1 May 2023), two confirmed cases were reported from Bata district (Figure 3). These cases had a known epidemiological link to a confirmed case, through a family cluster or through a healthcare setting.

The United Republic of Tanzania:

Since the declaration of the MVD outbreak on 21 March 2023, a total of nine cases (eight laboratory-confirmed and one probable case) have been reported as of 30 April 2023 (Figure 4). Among the total cases, six deaths were recorded (CFR 66.7%). Among the confirmed cases, three have recovered, and two have been reported among healthcare workers, one of whom died .

In the last 21 days, from 10 to 30 April, one confirmed case was reported on 11 April. This case was the mother of a previously reported MVD case, a child of 18 months old, who died on the same day. The mother was quarantined as soon as MVD was detected in the child in March. No further contacts linked to this case have been reported. There are currently no confirmed cases in the treatment centre in Bukoba following the discharge of the confirmed patient on 21 April 2023. This brings the total of survivors to three since the outbreak was declared.

All cases are reported from Bukoba district in Kagera Region.

Cases ranged in age from 1 to 59 years old (median 35-year-old), with males being the most affected (n= 6; 66.7%).

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 bodily 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 deceased's body 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.

Although no vaccines or antiviral treatments are approved to prevent or treat the virus, Remdesivir is being used on a modified, monitored emergency-use basis in Equatorial Guinea. 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 is the first reported outbreak of MVD in both 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 and1998), Kenya (1990, 1987, 1980) and South Africa (1975).

Public health response in both countries: See https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON467

WHO risk assessment

Both countries have reported MVD outbreaks for the first time.

In Equatorial Guinea, while many cases are linked within a social network/gatherings or by geographic proximity, the earlier presence of cases and/or clusters across multiple districts without clear epidemiologic links may indicate undetected virus transmission. The last cases occurred in Bata, the most populated city and economic hub of Equatorial Guinea, with an airport and seaport, posing challenges for the response. The country surveillance system remains suboptimal, with few alerts reported. Additionally, there are population movements between the different districts of the mainland and island regions. Frequent population movements and porous land borders are also reported in the districts bordering Cameroon and Gabon, with suboptimal surveillance at land entry points and countless uncontrolled paths or trails along the border with Cameroon and Gabon.

In the United Republic of Tanzania, the affected region, Kagera, borders three countries (Uganda to the north, and Rwanda and Burundi to the west) and Lake Victoria, and cross-border population movements may increase the risk of disease spread. Following the recent Ebola virus outbreaks in the Democratic Republic of the Congo from 23 April - 3 July 2022 and from 21 August - 27 September 2022, and Sudan ebolavirus outbreak in Uganda from 20 September 2022 to 11 January 2023, neighbouring countries in the subregion, including the United Republic of Tanzania, have been building preparedness capacities against filovirus diseases. However, an epidemiological investigation, which is still being carried out, has not revealed the source of the outbreak which may pose an additional risk to the population in the affected district.

In March 2023, WHO assessed the public health risk posed by the MVD outbreaks in Equatorial Guinea and the United Republic of Tanzania as very high at the national level, high at the sub-regional level, moderate at the regional level, and low at the global level. WHO continues to monitor the situation in these two countries closely.

WHO advice

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

Health workers caring for patients with confirmed or suspected MVD should apply IPC measures including, standard and transmission-based precautions and wearing personal protective equipment and performing hand hygiene to avoid contact with the patient’s blood and body fluids and with contaminated surfaces and objects. Health facilities should ensure environmental controls, such as adequate water, sanitation and hygiene, as well as that safe infectious waste management protocols are in place to enable health workers to practice IPC measures. In addition, healthcare facilities should conduct appropriate screening, isolation and referral of suspected cases. WHO recommends that male survivors of MVD practice safer sex for 12 months from onset of symptoms, or until their semen twice tests negative for the Marburg virus. 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 to strengthen surveillance in the country through alert management, case investigation, contact listing, tracing and follow up and active case search. In addition, WHO advises to strengthen surveillance at points of entry in the affected areas in Equatorial Guinea and the United Republic of Tanzania for the identification of cases, including through exit screening; to map cross-border population mobility to identify populations in vulnerable situations and target public health interventions; and to provide public health information and advice in all relevant languages in affected districts, at points of entry and in adjacent communities near land borders. Furthermore, suspect, probable and confirmed cases and their contacts should not undertake travel, including international. Based on available information, WHO advises against any other international travel and/or trade measures in Equatorial Guinea and the United Republic of Tanzania. States Parties adopting international travel- and trade-related measures potentially more restrictive than those advised by WHO, are invited to report them to WHO, pursuant to Article 43 of the International Health Regulations (2005).

Before initiating discussion on the 42-day countdown to declare the end of an outbreak, it is recommended that all listed contacts of confirmed or probable cases have completed their 21-day follow-up period with no symptoms. If not, there is still a possibility that a contact becomes a case.

Once all contacts have completed their 21-day period, the date of last possible exposure to a MVD probable or confirmed case can be set, based on two possible scenarios:

• The person was a confirmed positive case. He/she recovered and later tested negative by polymerase chain reaction (PCR) on two blood samples collected at an interval of at least 48 hours. The 42-day count starts on the day after the day on which the second negative PCR sample was collected.

• The person was a confirmed or probable MVD case. He/she died and a burial was organized. The 42-day count begins the day after the burial.

Further information

Citable reference: World Health Organization (8 May 2023). Disease Outbreak News; Marburg virus disease - Equatorial Guinea and the United Republic of Tanzania. Available at https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON467

1. https://alima.ngo/2022/12/08/cube/

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