Marburg and Ebola Virus Infections
Marburg and Ebola are filoviruses that cause hemorrhage, multiple organ failure, and high mortality rates. Diagnosis is with enzyme-linked immunosorbent assay, PCR, or electron microscopy. Treatment is supportive. Strict isolation and quarantine measures are necessary to contain outbreaks.
(See also Overview of Arbovirus, Arenavirus, and Filovirus Infections.)
Marburg and Ebola viruses are filamentous filoviruses that are distinct from each other but that cause clinically similar diseases characterized by hemorrhagic fevers and capillary leakage. Ebola virus infection is slightly more virulent than Marburg virus infection.
Ebola virus isolates have been differentiated into 5 species:
Most previous outbreaks of Marburg and Ebola virus infections have originated in sub-Saharan Central and West Africa. Past outbreaks have been rare and sporadic; they have been contained partly because they have occurred in isolated areas. Spread to other areas, when it occurs, has usually resulted from travelers returning from Africa. However, in 1967, a small Marburg hemorrhagic fever outbreak occurred in Germany and Yugoslavia among laboratory workers who had been exposed to tissues from imported green monkeys.
In December 2013, a large Ebola virus outbreak began in rural Guinea (West Africa), then spread to densely populated urban regions in Guinea and to neighboring Liberia and Sierra Leone. It was first recognized in March 2014. It has so far involved thousands of people and has a mortality rate of about 59%. Infected travelers have spread Ebola virus to Europe and North America. Cases of Ebola continued to occur in the first few months of 2016; Sierra Leone was finally declared Ebola-free in March 2016, Guinea, in May 2016, and Liberia, in June 2016.
Most index cases involve exposure to nonhuman primates in sub-Saharan Africa. The vector and reservoir are not known precisely, although the Marburg virus has been identified in bats, and cases have occurred in people exposed to bats (eg, in mines or caves). Ebola virus outbreaks have been linked to consumption of meat from wild animals in affected areas (bush meat) or soup made from bats. Ebola and Marburg virus infections have also occurred after handling tissues from infected animals.
Filoviruses are highly contagious. Human-to-human transmission occurs via skin and mucous membrane contact with body fluids (saliva, blood, vomit, urine, stool, sweat, breast milk, semen) of an infected symptomatic person or rarely a nonhuman primate. Humans are not infectious until they develop symptoms. Symptoms and signs persist in surviving patients for as long as it takes to develop an effective immune response. Typically, surviving patients eliminate the virus entirely and no longer transmit the virus; however, Ebola virus may survive in certain immune-privileged sites (eye, brain, testes). The virus may re-emerge from these sites and cause late sequelae or relapse. Semen can transmit Ebola and Marburg virus infection for up to 7 mo in contrast to other body fluids.
Aerosol transmission has been postulated; however, if it occurs, it is probably rare.
Real-world transmission is mainly human-to-human, resulting from close contact with the blood, secretions, other body fluids, or organs of infected people. Burial ceremonies in which mourners have direct contact with the deceased have played an important role in transmission of infection.
Symptoms of Marburg and Ebola virus infection are very similar.
After an incubation period of 2 to 20 days, fever, myalgia, and headache occur, often with abdominal pain, nausea, and upper respiratory symptoms (cough, chest pain, pharyngitis). Photophobia, conjunctival injection, jaundice, and lymphadenopathy also occur. Vomiting and diarrhea may soon follow. Delirium, stupor, and coma may occur, indicating CNS involvement.
Hemorrhagic symptoms begin within the first few days and include petechiae, ecchymoses, and frank bleeding around puncture sites and mucous membranes. A maculopapular rash, primarily on the trunk, begins around day 5.
Severe hypovolemia can develop, resulting from
Loss of electrolytes can cause severe hyponatremia, hypokalemia, and hypocalcemia. Cardiac arrhythmias can result.
During the 2nd wk of symptoms, either defervescence occurs and patients begin recovery, or patients develop fatal multiple organ failure. Recovery is prolonged and may be complicated by recurrent hepatitis, uveitis, transverse myelitis, and orchitis. Mortality ranges from 25 to 90%.
Marburg or Ebola virus infection is suspected in patients with bleeding tendencies, fever, other symptoms consistent with early filovirus infection, and travel from endemic areas. The CDC has issued an algorithm and guidelines for evaluating travelers returning from endemic areas (see Algorithm for Evaluation of the Returned Traveler and Think Ebola: Early recognition). A similar approach can be used if Marburg virus is suspected.
The WHO has also issued guidelines regarding the 2014 Ebola outbreak in West Africa (WHO Ebola situation reports: Archive).
Cases should be discussed with public health authorities, who can assist in all facets of management, including
Testing includes CBC, routine blood chemistries, liver function and coagulation tests, and urinalysis. Diagnostic tests include ELISA and RT-PCR. The gold standard is detection of characteristic virions with electron microscopy of infected tissue (especially liver) or blood.
No effective antiviral therapy exists. Treatment is supportive and includes the following:
Drugs are being tested, some under expedited procedures, but none have yet been proved effective and safe.
Several vaccines and antiviral drugs are currently in development but are unlikely to be available imminently.
To prevent spread, symptomatic patients with possible Ebola or Marburg virus infection must be isolated in dedicated containment facilities. Standard intensive care units (ICUs) in public hospitals are not suitable. Special containment facilities provide for total control of fluid effluent and respiratory products.
Staff members in contact with patients must be completely covered in protective suits with internal containment of respiratory gases. Trained staff members must be available to help those in contact with patients remove the protective clothing. Protocols for donning and removing mask, goggles or face shields, gown, and gloves must be followed (see the CDC's Sequence for Donning Personal Protective Equipment).
Thorough equipment sterilization, hospital closures, and community education have shortened previous epidemics.
All suspected cases, including the cadavers, require strict isolation and special handling.
For more information, see the WHO's interim recommendations for infection prevention and control.
Ebola and Marburg viruses, although distinct, cause similar hemorrhagic fevers; outbreaks are perpetuated mainly by human-to-human transmission via contact with infected body fluids.
Transmission in the 2013-2014 Ebola virus outbreak was predominantly human-to-human, resulting from close contact with blood, secretions, other body fluids, or organs of infected people or cadavers.
Suspect Marburg or Ebola virus infection in patients with bleeding tendencies, fever, other compatible symptoms, and travel from endemic areas.
Isolate patients with possible infection, and use strict procedures to protect workers who care for these patients.
Plan diagnosis, management, and prevention of transmission with public health authorities.