One of the peskier realities of the Ebola outbreak in West Africa is that the deadly disease cannot be identified until a person shows symptoms. It’s difficult to contain a virus when the earliest it can be diagnosed is the same point at which it becomes contagious. But a new study looking at the Ebola-like Marburg virus has found early markers of the disease, an important step in creating a screening test to detect infected people before they are able to spread the virus.
It's encouraging news, but it also raises a question. What is Marburg virus and should we be concerned about it?
The virus was first identified in 1967 during epidemics in Marburg and Frankfurt, Germany, and in Belgrade, Yugoslavia (now Serbia). Thirty-one people came down with the disease; most of them laboratory workers, plus some medical workers and family members who took care of them. Seven of the people died. The initial infections were introduced by African green monkeys that had been imported from Uganda for research.
The reservoir host of the Marburg virus is the African fruit bat (Rousettus aegyptiacus). It hasn’t been positively confirmed, but bats are suspected to be the natural host for Ebola as well. Although Marburg-infected bats don’t show symptoms of illness, when the virus spills into the primate population (including humans), the consequences can be lethal.
This African fruit bat is widely distributed in caves across Africa, and Marburg pops up throughout the continent. Confirmed cases have been reported in Uganda, Zimbabwe, the Democratic Republic of the Congo, Kenya, Angola and South Africa. All told, however, there have only been a dozen outbreaks on record, and many of those had only one case. A number of the initial cases started in workers who labored in bat-infested mines. Occasional cases have occurred outside of Africa as well. In 2008, a Dutch traveler and an American traveler developed Marburg after visiting a well-known cave inhabited by fruit bats in a national park in Uganda. The Dutch tourist died; the American recovered.
Both Marburg and Ebola belong to the small family of viruses known as Filoviridae, a group of diseases that can cause severe hemorrhagic fever in humans and nonhuman primates. So small is this family of filoviruses, in fact, that so far only two members have been identified, Marburg and Ebola. Within that, five species of Ebola virus have been identified: Taï Forest, Sudan, Zaire, Reston and Bundibugyo. Filoviruses have a different shape from other types of viral hemorrhagic fevers, which include dengue and yellow fever.
According to the World Health Organization, filoviruses are among the most virulent pathogens known to infect humans. And while Marburg is rare, it has the capacity to cause dramatic outbreaks with a high fatality rate.
The virus is transmitted by direct contact with the blood, body fluids and tissues of infected persons, as well as by handling infected wild animals (monkeys, fruit bats), either dead or alive.
Those infected with Marburg virus can expect the illness to appear after five to 10 days of incubation. Symptoms come on quickly and include fever, chills, headache and muscle pain. Around the fifth day, a prominent rash on the chest, back, and/or stomach may occur. Next up: nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea. Symptoms increase in awfulness and can include jaundice, inflammation of the pancreas, severe weight loss, delirium, shock, liver failure, multi-organ dysfunction and blood oozing out of orifices and injection sites. The fatality rate for Marburg virus varies widely between outbreaks, ranging from 23 to 90 percent.
Like Ebola, there is no vaccine or approved drug to treat the virus; the only treatment is general supportive therapy. But hopefully, an earlier screening test for both Marburg and Ebola could be on the way — and with it, the possibility of better containment of both of these vicious viruses.
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