Viral hemorrhagic 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.
The Special Pathogens Branch (SPB) primarily works with hemorrhagic fever
viruses that are classified as biosafety level four (BSL-4) pathogens. A
list of these viruses appears in the
SPB disease information index. The Division
of Vector-Borne Infectious Diseases, also in the National Center for Infectious
Diseases, works with the non-BSL-4 viruses that cause two other hemorrhagic
fevers, dengue hemorrhagic fever and
yellow fever.
How are hemorrhagic fever viruses grouped?
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) coating.
Their
survival is dependent on an animal or insect host, called the natural reservoir.
The viruses are geographically restricted to the areas where their host species
live. 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.
Human cases 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.
Kidney failure can occur from an acute event or a chronic condition or disease. Prerenal kidney failure is caused by blood loss, dehydration, medication. Some of the renal causes of kidney failure are from sepsis, medications, rhabdomyolysis, multiple myeloma, and acute glomerulonephritis. Post renal causes of kidney failure include bladder obstruction, prostate problems, tumors, or kidney stones. Treatment options included diet, medications, or dialysis.
Dengue fever is contracted from the bite of a striped Aedes aegypti mosquito. Symptoms of dengue include headache, fever, exhaustion, severe joint and muscle pain, rash, and swollen glands. Since dengue is caused by a virus, there is no specific medicine to treat it. Treatment instead focuses on relieving the symptoms.
Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). Fever is part of the body's own disease-fighting arsenal: rising body temperatures apparently are capable of killing off many disease- producing organisms.
Coma is the inability to waken or react to the surrounding environment. The Glasgow Coma Scale is frequently used to measure the depth of coma. Causes of coma include trauma, bleeding, edema, lack of oxygen, poisoning, or hypoglycemia. Prognosis for a patient in a coma depends on the cause of the coma.
Travelers' diarrhea is generally contracted by eating contaminated food or drinking contaminated water. Food is the primary source of travelers' diarrhea. Enterotoxigenic E. coli is the cause of up to 70% of all cases of travelers' diarrhea. There are five unique classes of E. coli that causes gastroenteritis. Other bacteria responsible for travelers' diarrhea include
Campylobacter, jejuni, shigella, and salmonella. Viruses such as rotavirus and Norwalk virus (norovirus) and giardia lamblia a parasite may cause travelers' diarrhea. Prevention is careful eating and drinking of water.
Ticks are known transmitters of disease to humans and animals. Tick-borne diseases include Lyme disease, Rocky Mountain spotted fever, Q fever, tularemia, babesiosis, and Southern tick-associated rash illness. Infected ticks spread disease once they've bitten a host, allowing the pathogens in their saliva and mouth get into the host's skin and blood. Tick bites are typically painless, but the site of the bite may later itch, burn, turn red, and feel painful. Individuals allergic to tick bites may develop a rash, swelling, shortness of breath, numbness, or paralysis. Tick bite treatment involves cleaning and applying antibiotic cream.
Medical shock is a life-threatening medical condition. There are several types of medical shock, septic shock, anaphylactic shock, cardiogenic shock, hypovolemic shock, and neurogenic shock. Causes of shock include heart attack, heart failure, heavy bleeding (internal and external), infection, anaphylaxis, spinal cord injury, severe burns, chronic vomiting or diarrhea. Low blood pressure is the key sign of sock. Treatment is dependant upon the type of shock.
Travelers should prepare for their trip by visiting their physician to get the proper vaccinations and obtain the necessary medication if they have a medical condition or chronic disease. Diseases that travelers may pick up from contaminated water or food, insect or animal bites, or from other people include malaria, meningococcal meningitis, yellow fever, hepatitis A, typhoid fever, polio, and cholera.
Bug bites and stings have been known to transmit insect-borne illnesses such as West Nile virus, Rocky Mountain spotted fever, and Lyme disease. Though most reactions to insect bites and stings are mild, some reactions may be life-threatening. Preventing bug bites and stings with insect repellant, wearing the proper protective attire, and not wearing heavily scented perfumes when in grassy, wooded, and brushy areas is key.
Typhus is a disease caused by Rickettsia bacteria. Symptoms and signs include fever, headache, nausea, vomiting, diarrhea, and rash. Antibiotics are recommended as the treatment for endemic and epidemic typhus infections.
The kidneys play key roles in body function, not only by filtering the blood
and getting rid of waste products, but also by balancing levels of
electrolyte levels in the body, controlling blood pressure, and stimulating the
production of red blood cells.
The kidneys are located in the abdomen toward the back, normally one on each
side of the spine. They get their blood supply through the renal arteries
directly from the aorta and send blood back to the heart via the renal veins to
the vena cava. (The term "renal" is derived from the Latin name for kidney.)
The kidneys have the ability to monitor the amount of body fluid, the
concentrations of electrolytes like sodium and potassium, and the acid-base
balance of the body. They filter waste products of body metabolism, like urea
from protein metabolism and uric acid from DNA breakdown. Two waste products in
the blood can be measured: blood urea nitrogen (BUN) ...
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