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Marburg Virus |
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 The
Marburg virus is the causative agent of Marburg hemorrhagic fever. Both the
disease and virus are related to Ebola and originate in the same part of Africa
(Uganda and Eastern Congo). The zoonosis is of unknown origin, but some
scientists believe it may be hosted by bats.
The disease is spread through bodily fluids, including blood, excrement, saliva,
and vomit. There is no cure or vaccine for this deadly and infectious virus.
Victims suffer a high fever, diarrhea, vomiting, and severe bleeding from bodily
orifices and usually die within a week. Fatality rates range from 25 to 100%.
In the spring of 2005, the virus attracted widespread press attention for an
outbreak in Angola. Beginning in October 2004 and continuing into 2005, the
outbreak was the world's worst epidemic of any kind of hemorrhagic fever.
The Marburg Virus
The viral structure is typical of filoviruses, with long threadlike particles
which have a consistent diameter but vary greatly in length from an average of
800 nanometers up to 14,000 nm, with peak infectious activity at about 790 nm.
Virions (viral particles) contain seven known structural proteins. While nearly
identical to Ebola virus in structure, Marburg virus is antigenically distinct
from Ebola virus — in other words, it triggers different antibodies in infected
organisms. It was the first filovirus to be identified.
Infection Details
Because many of the signs and symptoms of Marburg hemorrhagic fever are similar
to those of other infectious diseases, such as malaria or typhoid, diagnosis of
the disease can be difficult, especially if only a single case is involved.
The disease is characterised by the sudden onset of fever, headache, and muscle
pain after an incubation period of 3-9 days. Within a week, a maculopapular rash
develops, followed by vomiting, chest and abdominal pain, and diarrhea. The
symptoms soon increase in severity leading to jaundice, delirium, organ failure,
and extensive hemorrhage. Patients generally die from hypovolemic shock as fluid
leaks out of the blood vessels, causing blood pressure to drop. Depending upon
health care and hospitalization support, the disease can have very high fatality
rates, with estimates ranging from 25% up to 100%. If a patient survives,
recovery from the disease is prolonged and can be marked by inflammation or
infection of various organs, including: orchitis (testicles), hepatitis (liver),
transverse myelitis (spinal cord), uveitis (eyes), or parotitis (salivary
glands).
Infection is believed to be spread by close contact with body fluids of those
infected. The virus is unlikely to spread through casual contact. Patients are
most contagious during the acute phase of the illness when fluids such as vomit
and blood are present. Unsafe burial practices such as embracing, kissing or
ritual bathing of the corpse present another infection vector.
According to a report in The New York Times, the virus moves very quickly. "On
Day 3 of the infection, fewer than 200 viruses are in a drop of blood. By Day 8,
there are five million."
Treatment and Prevention
As with other hemorrhagic fever viruses, the treatment options for Marburg are
limited. Hypotension and shock may require early administration of vasopressors
and haemodynamic monitoring with attention to fluid and electrolyte balance,
circulatory volume, and blood pressure. Viral hemorrhagic fever (VHF) patients
tend to respond poorly to fluid infusions and rapidly develop pulmonary edema.
This is especially true of patients infected with Hantaan and Seoul viruses.
Patient caregivers require barrier infection control measures including double
gloves, impermeable gowns, face shields, eye protection, leg and shoe coverings.
A few research groups are working on drugs and vaccines to fight the virus. In
2002, Genphar, a company doing research for the United States Army's bio-defense
program, announced that an experimental vaccine protected animals from a high
dose of Marburg virus. The tests were conducted by the United States Army
Medical Research Institute of Infectious Diseases (USAMRIID). According to the
company, all animals in the control group died within days whereas all animals
that received the regular dosage of the vaccine were fully protected. The
company has moved on to non-human primate trials. Late in 2003, the US
government awarded the company a contract worth $8.4 million for what was
described as "a multivalent Ebola, Marburg filovirus vaccine program".
In June 2005 scientists at Canada's National Microbiology Laboratory announced
that they had also developed vaccines for both Marburg and Ebola that showed
significant promise in primate testing. Studies on mice also suggested that the
vaccine might be an effective treatment for the disease if it is administered
shortly after a patient is infected. To make the vaccines the scientists fused a
surface protein from the viruses they hope to protect against onto an animal
virus - vesicular stomatitis - which is thought to be of no threat to humans. In
the rhesus macaque monkey model of the disease, the vaccine is effective even
when given after infection with the virus.
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