New Outbreaks in Africa Raise Alarms About Marburg, a Deadly Cousin of Ebola

Two simultaneous outbreaks of Marburg virus, a close cousin of Ebola that can kill up to 90% of the people it infects, are raising critical questions about the behavior of this mysterious bat-born pathogen and global efforts to prepared for possible pandemics.

Marburg, a hemorrhagic fever, is rare: Only a handful of outbreaks have been reported since the virus was identified in 1967. But a steady increase in cases in Africa in recent years is raising alarm.

Marburg causes high fever, vomiting, diarrhea and, in the most severe cases, bleeding from holes. It is spread between people through direct contact with the blood or other body fluids of infected people and with surfaces and materials such as clothing contaminated with these fluids.

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One of the two outbreaks, in Tanzania in East Africa, appears to have been brought under control, with only two people remaining in quarantine. But elsewhere, in Equatorial Guinea on the west coast, the spread of the virus is continuing and the World Health Organization said last week that the country was not transparent in reporting cases.

There are no treatments or vaccines for Marburg, but there are several candidates that have shown promise in phase 1 clinical trials. However, these candidates must be tested in active outbreaks to prove they work, and so far, no vaccine supply has been delivered to be tested in actual outbreaks.

“The moment an outbreak is detected, there has to be a mechanism to move quickly,” said Dr. John Amuasi, head of the global health department at the Kwame Nkrumah University of Science and Technology in Ghana, who investigated an outbreak of Marburg in the latter country. year.

The WHO and others are good at responding quickly to control the spread of a virus, he said, but lack a similarly quick response for research. It requires ready-to-ship stocks of vaccine candidates and researchers equipped to operate without further burdening an already struggling health system; nor does it currently exist.

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The WHO says it has drawn up a research protocol that can be applied to these outbreaks and to any other filovirus – the family that includes Marburg and Ebola – and it has been trying for more than a month to carry out the trials, working against a schedule. that goes

If the outbreak response works well—isolating cases and tracing contacts—the epidemic will quickly be brought under control, which appears to be the case in Tanzania. If the response does not go so well (as in Equatorial Guinea), there are fears of a widespread outbreak and a redoubled need for vaccination.

When an Ebola outbreak began in Uganda in September 2022, the type that quickly took off was the one for which there was no vaccine, but, similarly, there was a strong candidate waiting for a chance to be tested. The researchers announced plans to test it in Uganda. But the outbreak was over by the time the vaccine doses arrived.

The outbreaks in Equatorial Guinea and Tanzania are the first reported in either country. The outbreak in Equatorial Guinea began in January. The government has reported the deaths of nine people with confirmed Marburg virus disease and the deaths of another 20 people related to confirmed cases who have not been tested but are considered probable cases.

The government of Equatorial Guinea has released limited information about the outbreak, and the WHO has said there are likely undetected chains of transmission and that not all known cases are clearly linked to each other, suggesting a wider spread than it was thought before.

“WHO is aware of additional cases and we have asked the government to report these cases officially to WHO,” said Dr. Tedros Adhanom Ghebreyesus, the agency’s director, last week.

The outbreak in Tanzania was first reported in March. Five people with confirmed Marburg infections have died there, including a health care worker.

No new cases have been reported in Tanzania for two weeks, but the incubation period in Marburg is 21 days, so the outbreak is considered active.

“This is the hard part, with people in isolation, waiting for days,” said Kheri Issa, the Tanzania Red Cross’s Marburg viral disease response manager, in a telephone interview from the Kagera area where the disease broke out.

The WHO said both outbreaks pose regional risks: Equatorial Guinea has porous borders with Cameroon and Gabon, and so far cases have appeared in geographically widespread parts of the country. In Tanzania, Kagera region has busy borders with Uganda, Rwanda and Burundi.

These outbreaks follow one in Ghana last year and one in Guinea the year before – a marked change from sporadic occurrences in previous years. Amuasi said better tracking likely contributed to what appeared to be an increase in cases. As part of the response to the COVID-19 pandemic, he said, every African country improved its PCR testing capacity and infectious disease surveillance, meaning Marburg is being diagnosed more frequently.

But it suggests that historically there may have been more of the virus circulating among people than previously thought, Amuasi said, and the way it sickens people may be different than understood.

Dr. Nancy Sullivan, director of the National Infectious Disease Laboratories at Boston University, said she believes climate change, and the way it is changing the behavior of people and animals, is driving the current surge in cases. “We’re hitting a lot more reservoirs” of the virus, she said.

Sullivan created the most advanced Marburg vaccine candidate when she worked with the National Institute of Allergy and Infectious Diseases. It showed safety and immune response in a phase 1 clinical trial, and the Sabin Vaccine Institute, a Washington-based nonprofit that promotes global vaccine development, is continuing the testing process.

The Sabin Institute said it had 600 doses of the vaccine bottled and ready to use and planned for an eventual stockpile of 8,000 by the end of this year. Sullivan said 600 doses would be enough to start a ring vaccination trial of those at risk in Tanzania and Equatorial Guinea.

But the WHO has yet to announce operational details for a trial of this or three other vaccine candidates. Transporting the doses to the site is just one challenge; a trial would require a principal investigator from the outbreak site, legal agreements with vaccine manufacturers and regulatory approval. Equatorial Guinea has an extremely dark government that has been under the control of President Teodoro Obiang Nguema Mbasogo and his family for more than 30 years.

Without dedicated resources and pre-approved testing protocols, filovirus outbreaks will continue to occur with little progress on interventions that can stop them, Amuasi said.

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