Fevers Survival, Symptoms and Information
The History of Bioterrorism: Viral Hemorrhagic Fevers
What Are Viral Hemorrhagic Fevers (VHFs)?
fevers (VHFs) refer to a group of illnesses that are caused by
several distinct families of viruses. In general, the term
"viral hemorrhagic fever" is used to describe a severe
multisystem syndrome (multisystem in that multiple organ systems
in the body are affected). Characteristically, the overall
vascular system is damaged, and the body's ability to regulate
itself is impaired. These symptoms are often accompanied by
hemorrhage (bleeding); however, the bleeding is itself rarely
life-threatening. While some types of hemorrhagic fever viruses
can cause relatively mild illnesses, many of these viruses cause
severe, life-threatening disease.
VHFs are caused
by viruses of four distinct families: arenaviruses, filoviruses,
bunyaviruses, and flaviviruses. Each of these families share a
number of features:
They are all RNA
viruses, and all are covered, or enveloped, in a fatty (lipid)
Their survival is
dependent on an animal or insect host, called the natural
The viruses are
geographically restricted to the areas where their host
Humans are not
the natural reservoir for any of these viruses. Humans are
infected when they come into contact with infected hosts.
However, with some viruses, after the accidental transmission
from the host, humans can transmit the virus to one another.
or outbreaks of hemorrhagic fevers caused by these viruses
occur sporadically and irregularly. The occurrence of
outbreaks cannot be easily predicted.
With a few
noteworthy exceptions, there is no cure or established drug
treatment for VHFs.
In rare cases, other viral and bacterial infections can cause
a hemorrhagic fever; scrub typhus is a good example.
What carries viruses that cause viral hemorrhagic fevers?
with most VHFs are zoonotic. This means that these viruses
naturally reside in an animal reservoir host or arthropod
vector. They are totally dependent on their hosts for
replication and overall survival. For the most part, rodents and
arthropods are the main reservoirs for viruses causing VHFs. The
cotton rat, deer mouse, house mouse, and other field rodents
are examples of reservoir hosts. Arthropod ticks and mosquitoes
serve as vectors for some of the illnesses. However, the hosts
of some viruses remain unknown --
Marburg viruses are well-known examples.
hemorrhagic fever viruses transmitted?
hemorrhagic fever are initially transmitted to humans when the
activities of infected reservoir hosts or vectors and humans
overlap. The viruses carried in rodent reservoirs are
transmitted when humans have contact with urine, fecal matter,
saliva, or other body excretions from infected rodents. The
viruses associated with arthropod vectors are spread most often
when the vector mosquito or tick bites a human, or when a human
crushes a tick. However, some of these vectors may spread virus
to animals, livestock, for example. Humans then become infected
when they care for or slaughter the animals.
Some viruses that
cause hemorrhagic fever can spread from one person to another,
once an initial person has become infected.
Lassa and Crimean-Congo hemorrhagic fever viruses are
examples. This type of secondary transmission of the virus can
occur directly, through close contact with infected people or
their body fluids. It can also occur indirectly, through contact
with objects contaminated with infected body fluids. For
example, contaminated syringes and needles have played an
important role in spreading infection in outbreaks of Ebola
hemorrhagic fever and Lassa fever.
What are the
symptoms of viral hemorrhagic fever illnesses?
Specific signs and
symptoms vary by the type of VHF, but initial signs and symptoms
often include marked fever, fatigue, dizziness, muscle aches,
loss of strength, and exhaustion. Patients with severe cases of
VHF often show signs of bleeding under the skin, in internal
organs, or from body orifices like the mouth, eyes, or ears.
However, although they may bleed from many sites around the
body, patients rarely die because of blood loss. Severely ill
patient cases may also show shock, nervous system malfunction,
coma, delirium, and seizures. Some types of VHF are associated
with renal (kidney) failure.
patients with viral hemorrhagic fever treated?
supportive therapy, but generally speaking, there is no other
treatment or established cure for VHFs. Ribavirin, an anti-viral
drug, has been effective in treating some individuals with Lassa
fever or HFRS. Treatment with convalescent-phase plasma has been
used with success in some patients with Argentine hemorrhagic
How can cases of viral hemorrhagic fever be prevented and
With the exception
of yellow fever and Argentine hemorrhagic fever, for which
vaccines have been developed, no vaccines exist that can protect
against these diseases. Therefore, prevention efforts must
concentrate on avoiding contact with host species. If prevention
methods fail and a case of VHF does occur, efforts should focus
on preventing further transmission from person to person, if the
virus can be transmitted in this way.Because many of the hosts
that carry hemorrhagic fever viruses are rodents, disease
prevention efforts include
rodents from entering or living in homes or workplaces;
cleanup of rodent nests and droppings.
fever viruses spread by arthropod vectors, prevention efforts
often focus on community-wide insect and arthropod control. In
addition, people are encouraged to use insect repellant, proper
clothing, bednets, window screens, and other insect barriers to
avoid being bitten.
hemorrhagic fever viruses that can be transmitted from one
person to another, avoiding close physical contact with infected
people and their body fluids is the most important way of
controlling the spread of disease. Barrier nursing or infection
control techniques include isolating infected individuals and
wearing protective clothing. Other infection control
recommendations include proper use, disinfection, and disposal
of instruments and equipment used in treating or caring for
patients with VHF, such as needles and thermometers.
In conjunction with
the World Health Organization, CDC has developed practical,
hospital-based guidelines, titled
Infection Control for Viral Haemorrhagic Fevers In the African
Health Care Setting. The manual can help health-care
facilities recognize cases and prevent further hospital-based
disease transmission using locally available materials and few
Information and updates here: