Marburg virus

Marburg virus (MARV) is the etiologic agent responsible for Marburg virus disease (MVD) in humans, with a mortality rate ranging from 23 to 90 percent, depending on the outbreak. It is a member of the family Filoviridae, which includes the genera Marburgvirus, Ebolavirus, Cuevavirus, Striavirus, and Thamnovirus. Although generally less well known than its cousin Ebola virus (EBOV), MARV was first discovered following outbreaks in Germany and Belgrade, former Yugoslavia. The first cases were detected in monkey specimens imported from Uganda that infected researchers in some laboratories. As many as 25 primary infections led to the death of 7 individuals. The virus then reappeared in 1975 in South Africa, again in 1980 and in 1987 in Kenya, very few cases were immediately isolated. More violent outbreaks occurred instead between 1998 and 2000 in the Democratic Republic of Congo and in 2004 in Angola, with more than a hundred deaths.

Transmission between humans occurs through direct contact with blood, secretions, organs or other body fluids of infected persons. The virus is not transmitted during the incubation period, which lasts from 3 to 9 days. Instead, the time when the patient is most contagious is during the acute phase of the disease, especially during hemorrhagic manifestations. Infection is facilitated by poor sanitary conditions, which are frequently found in low-income countries, and where people are in direct contact with the sick person and infected surfaces and materials. Funeral ceremonies where relatives and friends have direct contact with the body of the deceased also play a significant role in the transmission of the virus. Health care workers have been infected while treating Marburg patients due to close contact without proper infection control precautions and inadequate barrier nursing procedures. To date, about 9% of Ebola or Marburg victims have been health care workers.

Diseases in this group occur widely in tropical and subtropical regions. Ebola hemorrhagic fevers, Marburg fever, and Lassa fever occur in sub-Saharan Africa. m In 1999, an outbreak was identified in the Democratic Republic of the Congo, where multiple spillover events are thought to have occurred in the human population over the next 2 years. This outbreak resulted in a total of 154 cases, with a mortality rate of 83%. In 2005, the largest documented outbreak of MARV occurred in Angola with 252 documented human infections and 227 deaths; a mortality rate of 90%. Outbreaks have continued since 2005, recording one outbreak in 2007 in Uganda, two cases in 2008 involving tourists visiting Uganda returning home to the United States and the Netherlands. Subsequent outbreaks then developed in Uganda in 2012, 2014, and 2017. All of the recorded MARV outbreaks originated in Africa. Several bat species have been identified as a host reservoir for the virus, the most highly-rated among them being Rousettus aegyptiacus, the Egyptian fruit bat. Numerous cases have been reported among tourists and miners, who most likely contracted MARV in caves inhabited by these animals. The live virus was isolated from R. aegyptiacus bats inside the Kitaka cave in Uganda, the place where the miners diagnosed with MVD had worked.

There are few detailed clinical descriptions of MVD because of the rural nature of most outbreaks in Africa; therefore, the availability of pathological and laboratory data is limited. The detailed descriptions that do exist come from the initial outbreak in Marburg, Germany, and the outbreak in Johannesburg, South Africa, which involved three patients and a few isolated cases. Similar to many other infectious diseases, MVD cases initially report flu-like symptoms such as chills, fever, headache, sore throat, muscle pain, joint pain, and malaise, which emerge between 2 and 21 days after the initial infection. Within 2-5 days after the first symptoms, patients may experience abdominal pain, nausea, vomiting, watery diarrhea, and lethargy. On days 5-7, the intensity of the disease increases and may include a maculopapular rash spreading from the trunk to the limbs, conjunctivitis, sustained fever, and hemorrhagic fever symptoms, such as mucosal bleeding, petechiae, blood in the stool, vomiting, and bleeding from venipuncture sites. The maculopapular rash begins as small dark red spots around the hair follicles on the trunk and sometimes on the upper arms, developing into a diffuse rash and may become a dark erythema covering the face, neck, chest, and arms. Neurological symptoms such as confusion, agitation, increased sensitivity, seizures, and coma may occur in the later stages of the disease. Patients recover from the disease or die from dehydration, internal bleeding, organ failure, or some combination of systemic factors facilitated by a dysregulated immune response to the virus. Patients who survive generally do not experience the severe symptoms of the advanced stage, but may experience sequelae such as arthritis, conjunctivitis, myalgia, and symptoms of psychosis during and after recovery.

Marburg virus infection should be suspected in patients with a predisposition to bleeding, fever, and other symptoms in agreement with previous filovirus infection, returning from travel to endemic areas.
Tests useful in identifying the disease include CBC with formula, routine blood tests, liver function tests, coagulation tests, and urinalysis.
Diagnostic tests include enzyme-linked immunosorbent assay (ELISA) and RT-PCR (Real Time, Polymerase Chain Reaction). The reference method for diagnosis is identification of characteristic virions by electron microscopy of infected tissue or on blood.

There is no specific therapy for Marburg. The only treatment is to assist the patient wherever possible by trying to replenish his or her water and electrolyte supply, providing oxygen and performing blood transfusions.
Several candidate drugs are in development, showing promising results, but their safety and efficacy in humans is not yet known.

There are no licensed vaccines or treatments for MVD, in part because of the difficulty of performing clinical trials given the severity, infrequency, and rural nature of MVD outbreaks.
For travelers visiting a country where an outbreak of Marburg is occurring, it is advisable to gather information about the disease prior to travel so as to seek immediate medical attention at the first symptom of fever, adopt stringent hygiene practices (such as washing hands frequently), and do not eat bushmeat, such as chimpanzee or monkey meat.