The CDC warns of the "potential" of cases of the deadly Marburg virus

The CDC warns of the "potential" of cases of the deadly Marburg virus in the United States.

In recent months, an outbreak of the Marburg virus, a close relative of the Ebola virus that causes severe and often fatal human diseases, has been confirmed in Africa. And health officials have raised concerns about the rare virus, which has no cure or vaccine, and the possibility of its spread.

The bat-borne virus began making headlines in February when Equatorial Guinea confirmed to the World Health Organization its first-ever Marburg outbreak — since then, the country has reported 14 confirmed cases and ten confirmed deaths.

The following month, Tanzania declared an outbreak of Marburg disease, which has caused eight confirmed cases and five deaths, according to the World Health Organization.

On Thursday, April 6, the US Centers for Disease Control and Prevention issued a health advisory to inform public health departments and physicians in the United States about these outbreaks and to raise awareness about the "possibility of imported cases" — even though there are no cases associated with these outbreaks. It has been reported in the United States or other countries outside Tanzania and Equatorial Guinea.

The CDC has also issued travel advisories for Tanzania and Equatorial Guinea, urging travelers to these countries to exercise precautions, avoid contact with sick people and bats, and monitor for symptoms for at least three weeks after departure.

What is the Marburg virus?

Marburg virus was first identified in 1967 and has caused a few outbreaks since then, primarily in Africa, per the CDC.

"Marburg virus is part of a family of viruses that we call hemorrhagic fever viruses, and it is closely related to Ebola," Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center.

"The natural host or natural reservoir for Marburg virus is fruit bats," Schaffner adds, but the virus can periodically leave animals, cross the species barrier and enter human populations.

In humans, Marburg virus causes Marburg virus disease (MVD), a severe and fatal hemorrhagic fever, a condition that can affect many organ systems and damage the cardiovascular system, according to the CDC.

Marburg's average fatality rate is 50%, according to the World Health Organization, but the fatality rate in previous outbreaks has ranged from 25% to around 90%, Ph.D., professor of global health and epidemiology at George Mason University School of Public Health.

According to the Centers for Disease Control and Prevention (CDC) health advisory, most experts agree that the outbreaks in Equatorial Guinea and Tanzania are two independent animal-to-human transmission events, and there is no evidence to suggest these two outbreaks are related.

What are the symptoms of Marburg disease?

Initial symptoms of Marburg include a sudden fever, chills, headache, and muscle aches, according to the CDC. Within a few days, Schaffner adds, diarrhea, vomiting, nausea, and sore throat, chest, or abdomen may begin—some people develop a rash.

According to the World Health Organization, severe symptoms usually begin five to seven days after onset and typically involve profuse bleeding (bleeding) from multiple orifices, similar to Ebola, says Ross. Experts pointed out that internal bleeding can cause blood in stool and vomiting, and a person may bleed from his nose, eyes, or gums.

According to the CDC, these symptoms can progress, and the person may experience rapid weight loss, liver failure, pancreatitis, delirium, and multiple organ dysfunction. "It involves the entire body," notes Schaffner. Blood loss and other symptoms can lead to death.

"There's a perception that people will always bleed everywhere...but that's not the case... it's only when the condition is very serious that you have the bleeding part," says Ross.

According to the World Health Organization, Marburg can look similar to typhoid or malaria in the early stages or less severe cases, making diagnosis difficult. Royce adds that Marburg was diagnosed through lab tests.

How does the Marburg virus spread?

"The disease is transmitted when people come into close contact with infected body fluids, blood, or contaminated surfaces, very similar to Ebola," says Royce. Experts noted that Marburg is not airborne.

These body fluids include vomit, stool, urine, saliva, sweat, breast milk, amniotic fluid, semen, and vaginal fluids, according to the CDC, which can transmit the Marburg virus to another person through broken skin or mucous membranes in the mouth and nose, for example.

The virus often spreads in close environments or through families, Schaffner says. He adds that transmission can occur when someone, whether a family member or healthcare provider, cares for an infected person without proper infection control precautions.

The duration of infection and onset of symptoms ranges from 2 to 21 days, per the CDC.

"In the early stages of the disease, Marburg virus was not highly transmissible," Dr. Peter Hotez, co-director of the Texas Children's Hospital Center for Vaccine Development and expert in neglected tropical diseases.

However, when MVD becomes severe or reaches the bleeding stage, "you get huge numbers of virus particles in the body, even at death," says Hotez. He adds that people can also become infected while handling the body of a recently dead person from Marburg.

How transmissible is Marburg disease?

Compared to infections that spread through the respiratory tract like COVID-19, Marburg spreads less easily because it requires direct contact with blood or bodily fluids, Schaffner says.

The "infectiousness" of a virus is described using a reproduction number, or R0, which represents the average number of people an individual infected with the virus can infect, Hotez says.

At the top of the scale, measles has an R0 between 12 and 18, Hotez says. "Ebola is closer to the bottom of the scale, and Marburg is also presumed. The R0 is more like a one to two," Hotez explains.

Hotez says Marburg can be easily controlled with proper isolation and case detection. It's also critical that health facilities take strict infection control precautions and that providers have adequate PPE to prevent transmission, Schaffner says.

However, outbreaks of the Marburg virus are very rare, and scientists are still trying to build more reliance on this mysterious virus. "One of the biggest problems is that we don't know much about this virus because we don't do much research or monitoring," says Royce.

Marburg virus disease treatment and vaccine

There is no specific treatment for Marburg virus disease, says Reuss. However, supportive care — such as oral fluid therapy, intravenous fluids, oxygen, or blood transfusions — can improve the chances of survival.

Schaffner says that the death rate in Marburg can vary depending on the resources available to provide supportive care.

"There are no authorized or approved vaccines; however, some vaccine candidates are in phase 1 trials," says Royce.

NBC News reported that the World Health Organization hopes to test one of its experimental Marburg vaccine candidates in Equatorial Guinea amid the current outbreak. "We hope that the vaccines will be deployed as part of clinical trials in this case as they were during the recent Ebola outbreak," Royce adds.

Schaffner says that one of the challenges ahead is determining whether vaccines that work in the lab also work in the field and can be deployed quickly enough during an outbreak.

How worried are people about the outbreak?

"We should be concerned for people in Tanzania and Equatorial Guinea, but the threat to those of us back home [in the US] is very low," says Schaffner. Those who live in or travel to areas close to outbreaks should take precautions and follow local public health instructions.

Schaffner says there have been a few cases of someone getting a viral infection from an outbreak like the Marburg virus happening now and then traveling back and getting sick in the United States or Europe, but that's very rare. "There is no immediate sense of anxiety," he adds.

"We're observers kind of out of touch with this, and we're sending resources, both CDC and physical resources, to Tanzania and Equatorial Guinea to help reduce these outbreaks," Schaffner says.

One of the questions Hotez says he usually asks is: Why are all these rare or new diseases emerging right now? In recent years we have seen Marburg, covid-19, smallpox, and more. Is it all coincidental?

Hotez says no, and that this combination of economic and social conditions and climate change "contributes to the dramatic increase in diseases transmitted from animals to humans."