EBOLA AND MARBURG VIRUSES
The Ebola and Marburg viruses are known as filoviruses.
Since the 1960s, they have been the source for approximately 20 outbreaks. Both
viruses have been prepared as biological weapons and cause great concern
because of the extreme virulence and high mortality rates associated with
infection.
The clinical course differs among patients, but often
includes fever, rash, and encephalitis. Symptoms usually occur rapidly, and
with both viruses, the course of the illness often progresses rapidly to
profound hemorrhage, organ destruction, and shock. The mortality rate
approaches 90%. When patients survive, the recovery period is often prolonged,
with weakness, malaise, and cachexia common.
Despite aggressive
research, the natural reservoirs for filoviruses have not yet been found, but
it is thought that humans are in-fected only incidentally after exposure to an
unrecognized host or by insect bite. Human-to-human transmission usually occurs
after exposure to blood or other body fluid. When transmission is percutaneous,
it appears that a very low inoculum of contam-inated blood is required for
transmission to occur. The virus can also be spread by mucous membrane
exposure. Although air-borne transmission does not appear to be a likely mode
of transmission, the possibility has not been entirely eliminated. All involved
in caring for patients with filoviruses must adhere to strict infection control
measures. It is advisable that systems be set up to have objective monitors to
ensure that each nurse or other health care worker wears complete protective
equipment in the form of cap, goggles, masks, gown, gloves, and shoe covers.
Because there have been no cases diagnosed in the United
States, it is likely that early signs of disease may be initially
mis-classified. The diagnosis should be considered in a patient who has a
febrile, hemorrhagic illness after traveling to Asia or Africa or who has
handled animals or animal carcasses from those parts of the world. Because
neither hospital nor local public health labo-ratories would be able to confirm
a diagnosis, the CDC should be contacted immediately when Ebola and Marburg
viruses are suspected to be the cause of illness.
No antivirals have been
approved or show promise against Ebola and Marburg. Treatment is largely
supportive maintenance of the circulatory system and respiratory systems. It is
likely that the infected patient would need ventilator and dialysis support
through the acute phases of illness.
Supportive care for a
patient with such a devastating disease requires psychological support for the
patient and family. The natural fear of an untreatable, aggressive disease
would likely be intensified because of the rarity of the disease. The patient,
his family, health care workers, and others in the community will need
substantial, coordinated education about the known and unknown elements.
Intervention may be required from those trained to provide psychological
support for traumatic or terrorist events.
In March 2003, the World
Health Organization issued a global warning about the appearance of a newly
recognized type of pnemonia, Severe Acute Respiratory Syndrome (SARS). SARS is
an influenza-like disease, with patients presenting with fever and cough. A
minority will progress to experience respiratory distress. The disease was first
recognized in China, with a second genera-tion of cases erupting quickly in
Hong Kong, Vietnam, and over 17 other countries in a number of weeks.
The pattern of worldwide
dissemination was largely attributed to travel because of strong epidemiologic
evidence that patientsfrom many countries had shared common exposures. SARS
serves as an example of how suddenly benign microorganisms, es-pecially
viruses, can mutate to become important human pathogens. The epidemic
illustrates important principles of pub-lic health and infection control.
Before the disease came to the at-tention of the WHO, transmission to nurses
and other health care professionals occured frequently. Once patients were
appropri-ately isolated, with health care workers using barrier precautions and
cleaning contaminated surfaces carefully, transmission was ef-fectively reduced
or prevented.
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