Marburg virus, a rare but highly fatal infectious disease, is currently causing outbreaks in two African countries, Equatorial Guinea and Tanzania, for the first time. And although there are currently no cases in the United States, CDC  has issued an advisory warning providers to be on the lookout for any potential cases.

2 African countries report outbreaks of Marburg virus

According to CDC,  Marburg  is a "genetically unique zoonotic … RNA virus of the filovirus family" and is related to the Ebola virus. Since it was first identified in 1967, outbreaks of Marburg virus have periodically occurred in areas of Central and Southern Africa, including Angola and the Democratic Republic of Congo.

The virus is often transmitted to humans by African fruit bats after prolonged exposure in mines or caves that house large colonies of the animals. Once a person is infected, they can spread the virus to other humans through direct contact with bodily fluids or from surfaces contaminated with these fluids.

Marburg is highly infectious and has an incubation period of two to 21 days. Some symptoms include high fever, severe headache, severe malaise, muscle aches and pain, diarrhea, abdominal pain and cramping, nausea, and vomiting. In many cases, patients also develop severe bleeding or hemorrhaging at the end of their first week of symptoms.

The virus can also be quite deadly, with a fatality rate that ranges between 24% and 88%, depending on the specific strain of the virus and how cases are managed. Currently, there are no vaccines or antiviral treatments approved to treat Marburg virus.

Recently, two African countries confirmed their first outbreaks of the virus. In February, Equatorial Guinea reported its first cases of Marburg, and Tanzania reported its own outbreak of cases in March.

As of April 5, 14 lab-confirmed cases of Marburg have been identified in Equatorial Guinea, and of these cases, 10 were fatal. In Tanzania, there have been eight lab-confirmed cases, with five of them being fatal. According to CBS News, the outbreaks are "among the largest on the continent in a decade."

So far, there is no evidence to suggest that the outbreaks in Equatorial Guinea and Tanzania are related. Instead, most experts agree that these two outbreaks represent independent animal-to-human spillover events.

Currently, the  World Health Organization (WHO) is working with local health authorities in both countries to confirm the cause of the virus, as well as to establish control measures to limit the spread of the disease and end the outbreak as quickly as possible.

CDC issues advisory for potential imported Marburg cases

Although there have been no confirmed cases of Marburg outside of Equatorial Guinea and Tanzania, CDC last week issued an advisory in its Health Alert Network to caution health providers about the potential risk of imported cases.

"Currently, the risk of MVD [Marburg virus disease] in the United States is low; however, clinicians should be aware of the potential for imported cases," CDC said in its alert. "It is important to systematically assess patients for the possibility of viral hemorrhagic fever."

According to CDC, Marburg should be included as a differential diagnosis for patients with a history of concerning exposure while in an affected region. If a provider suspects a patient has Marburg virus, they should take a detailed travel history and the patient should be in isolation until a negative test is confirmed.

Providers who have concerns about a patient should also contact their jurisdictional health department right away and follow any protocols for patient assessment. "If a diagnosis of MVD is considered, jurisdictional officials will work with the CDC and the clinical team to coordinate care and testing for the patient and ensure appropriate precautions are taken to help prevent potential spread," CDC said.

While there are no approved vaccines or treatments for Marburg, but several manufacturers are working on potential vaccine candidates that could be deployed if needed, including one from the  Sabin Vaccine Institute that is backed by the U.S. government.

So far, 750 doses of that vaccine, which is based on a chimpanzee adenovirus, are ready to be deployed in trials for the current outbreaks. However, WHO has said that there is currently no agreed-upon date for the vaccine trials to begin.

"When the conditions may be favorable, the trials may be initiated," said WHO's Abdi Mahamud. "So right now is building the basics of good alert management and case management and other basics of the outbreak response. And at a future date may be considered, but as of now, we don't have a firm date for when it will start."

Separately, Thomas Geisbert, a professor in the department of microbiology and immunology at the  University of Texas Medical Branch, noted that "there are several experimental treatments that have been shown to protect animals against lethal Marburg virus infection." This includes a monoclonal antibody from  Mapp Biopharmaceutical and Gilead Sciences' COVID-19 antiviral remdesivir.

"Remdesivir is currently approved for human use for treating COVID-19," Geisbert said, "and the possible off-label use for Marburg is probably the most realistic and quickest intervention that could be deployed." (Henderson, MedPage Today, 4/6; Tin, CBS News, 4/6; Radcliffe, Healthline, 4/4; Hollowell, Becker's Hospital Review, 4/6; Christensen, CNN, 4/6)