Marburg Hemorrhagic Fever
Marburg Hemorrhagic Fever
Marburg Hemorrhagic Fever
Marburg hemorrhagic fever is one of a group of severe infections known as hemorrhagic fevers. The term hemorrhagic denotes the ability of these viral diseases to cause massive bleeding (hemorrhaging).
Marburg hemorrhagic fever is caused by a type of virus called a filovirus. The virus contains ribonucleic acid (RNA) as the genetic material. It was the discovery of the agent of Marburg hemorrhagic fever that led to the creation of the filovirus viral group. Other filoviruses identified so far include the four strains (types) of Ebola virus.
Both Marburg fever and Marburg virus were discovered in 1967. At that time, outbreaks of the fever occurred in three laboratories where scientists were studying the virus. One of these labs was located in the German city of Marburg, from which the name of both the disease and the virus was taken.
Over 30 people became ill during this initial outbreak. The source of the virus was found to be African green monkey tissues that had been imported to the lab from Uganda as part of an effort to develop a polio vaccine. Victims included not only laboratory staff who were directly exposed to the virus, but also family members and caregivers who contracted the illness from a staff member with the disease. This pattern of transmission helped to establish the contagious nature of the virus.
WORDS TO KNOW
ENDEMIC: Present in a particular area or among a particular group of people.
HEMORRHAGIC FEVER: A hemorrhagic fever is caused by viral infection and features a high fever and a high volume of (copious) bleeding. The bleeding is caused by the formation of tiny blood clots throughout the bloodstream. These blood clots—also called microthrombi—deplete platelets and fibrinogen in the bloodstream. When bleeding begins, the factors needed for the clotting of the blood are scarce. Thus, uncontrolled bleeding (hemorrhage) ensues.
HOST: Organism that serves as the habitat for a parasite, or possibly for a symbiont. A host may provide nutrition to the parasite or symbiont, or simply a place in which to live.
RESERVOIR: The animal or organism in which the virus or parasite normally resides.
The next reported case occurred in 1975, and it was determined to have been acquired in Zimbabwe. Another case was reported in 1980, this time in western Kenya. Cases reported in 1987 and 1998 also originated in other African countries.
The exact mechanism of transmission of the virus to humans is unknown. However, it is known that person-to-person transmission is possible, probably via contaminated blood or other body fluids. Other methods of transmission include handling medical equipment or touching surfaces that are contaminated with fluids infected with the virus.
Symptoms appear suddenly 5–10 days after infection. Presumably during this incubation period the virus is commandeering host cell replication machinery so that deoxyribonucleic acid (DNA) can be synthesized from the viral RNA, with that DNA then being used to produce the necessary components for new virus.
The symptoms of Marburg hemorrhagic fever include fever, chills, and headache. Initial symptoms may be mistaken for influenza. Approximately five days later, a rash appears mainly on the chest, stomach, and back. Nausea with vomiting, chest and abdominal pain, and diarrhea can develop. Subsequently, more severe symptoms may appear, including liver dysfunction with jaundice, pancreas inflammation, rapid weight loss, liver failure, and hemorrhaging. At this stage, organ failure often leads to a rapid death.
In the small number of cases known so far, the mortality rate is approximately 25%. Those who recover can display a number of recurring diseases, such as hepatitis.
Marburg hemorrhagic fever is endemic (naturally occuring) in Africa. So far, it has not been discovered to be indigenous to any other continent. As of 2007, the full distribution of the virus in Africa is still unclear, but seems to include western Kenya, Uganda, and possibly Zimbabwe. The only way to determine distribution presently is to wait for the appearance of an outbreak of the disease.
Primates are a suspected natural reservoir of the infection, since the 1967 German outbreak involved African monkeys. However, this assumption has not been proven. This situation is similar to that of the other known filovirus, the Ebola virus. The sporadic and devastating nature of past Ebola and Marburg hemorrhagic fever outbreaks have limited scientists’ ability to study the virus and determine its natural reservoir and potential hosts.
As of 2007, there is no cure or specific treatment for Marburg hemorrhagic fever. Rather, combating the infection involves standard precautions by attending physicians and other caregivers, such as handwashing and changing surgical garb before examining or tending to another patient. In addition, precautions to prevent the spread of the virus include wearing protective gowns, caps, foot covers, and masks equipped with face shields to guard against a spill or spray of blood. Treatment so far has been a catch-up effort designed to try and keep a patient stabilized and, in the worse cases, alive by the maintenance of blood pressure, fluid levels, and the proper concentrations of electrolytes. Also, ensuring that the blood remains capable of clotting can help reduce the loss of blood during hemorrhaging.
Even diagnosing the disease is challenging. In its early stages, the disease displays symptoms that are similar to influenza, malaria, and typhoid fever. In addition, once symptoms appear the disease can swiftly worsen.
The presence of the viral genetic material can be detected using a number of molecular techniques. This can confirm the presence of the virus just a few days after infection. However, because there have been so few cases to date and since Marburg hemorrhagic fever is not a disease that is easily studied in the laboratory, the diagnostic significance of these molecular advances is unclear.
Outbreaks of Marburg hemorrhagic fever are sporadic. This limits the number of people who are affected by the disease. However, this does not diminish the severity of the illness. The rapid onset of the disease and its high death rate can cause panic in communities that are affected.
Despite the rarity of Marburg hemorrhagic fever, outbreaks can occur. A recent example is the outbreak that occurred in 2005 in Uige, Angola, in which at least 270 people became ill. The death rate exceeded 90%. Another large outbreak occurred from 1998–2000 in the Democratic Republic of the Congo, in which 154 people became ill and 128 died.
Investigations of the 2005 Angolan outbreak determined that one cause was the unsafe use of needles to deliver injections in homes, medical clinics, and a pediatric ward. Re-use of the needles, which were intended to be used once and disposed of, facilitated in the spread of the virus. In the aftermath of the outbreak, the World Health Organization (WHO) instituted a safe injection campaign, which has helped reduce the re-use of contaminated needles in the region.
In both outbreaks, the isolated nature of the regions that were affected contributed to the spread of the disease. Medical care was rudimentary and clinics were not always adequately supplied to cope with the infection. Cultural practices, such as the open viewing and touching of the deceased prior to burial, also likely contributed to the spread of the virus. The WHO is working to increase awareness of the disease, especially in rural regions of countries such as Angola. With an increased understanding of the disease and its spread, it is hoped that alterations in behavior and cultural practices may help reduce the potential for future outbreaks.
Perhaps the greatest impact the disease has had is as an example of how diseases may be spreading from their natural, nonhuman hosts to humans. Identification of the natural host of a disease and the regions in which the natural host exists in greater numbers is vital if the disease is to be eradicated. In the case of Marburg hemorrhagic fever, the natural host is thought to be a primate.
Avoiding contact with primates in the wild (including their use as food) reduces the risk of contracting the disease.
The study of Marburg hemorrhagic fever requires a high containment facility called a biosafety type-4 lab, where air flow into and out of laboratories is controlled and stringent precautions regarding the wearing of protective clothing and decontamination following work with the virus are enforced. These steps help ensure that the virus does not escape from the lab and that researchers are protected from infection. Efforts to educate the medical community about Marburg symptomology are also important, since the virus can quickly infect health care workers and has the potential for rapid spread into the community. This potential for rapid person-to-person spread combined with the ferocity of the disease has heightened concerns that the Marburg virus could be used as an agent of bioterrorism.
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Centers for Disease Control and Prevention. “Marburg Hemorrhagic Fever.” March 3, 2006. <http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg.htm> (accessed May 7, 2007).