What are viral hemorrhagic fevers?

Causes and Symptoms

Viral hemorrhagic fevers are caused by a variety of viruses, including
members of the Arenaviridae, Bunyaviridae, Flaviviridae, and Filoviridae families, with the last mentioned being the one associated with diseases such as Ebola hemorrhagic fever and Marburg hemorrhagic fever. Many of the hemorrhagic diseases are zoonoses
that exist in reservoir species, such as bats, and are transmitted to humans through various modes; others are vector-borne. Crimean-Congo hemorrhagic fever, for example, is carried by ticks; humans become infected when they are bitten. In contrast, Ebola hemorrhagic fever, caused by a filovirus, is suspected of making the leap from animals to humans through the handling and eating of infected wild game, while Lujo fever, which is caused by an arenavirus, apparently infects humans when they inhale dust from rodent droppings. However, some viral hemorrhagic fevers may have the ability to aerosolize and thus may be transmitted person-to-person from an infected patient to caregivers or family members when an infected person sneezes or coughs. Contact with body fluids, such as blood or vomit, from an infected person can also cause the disease to spread.

The initial clinical signs and symptoms for viral hemorrhagic fevers are similar to those of many common illnesses, such as influenza or dysentery, with the patient complaining of a fever, headache, generalized aches and pains, or nausea. In the case of Ebola hemorrhagic fever, clinical signs may include a skin
rash or red eyes. It is usually not until several days after the onset of the illness that the hemorrhagic signs, such as bloody diarrhea indicating internal bleeding, appear. Because the symptoms for many hemorrhagic fevers are similar to those of common tropical diseases, initial diagnosis and quarantine efforts may be delayed.

The virulence of the hemorrhagic fevers varies, depending both on the specific viral strain involved and how quickly medical treatment is obtained. Despite the name hemorrhagic fever, it is rarely the blood loss associated with the diseases that causes death but instead the failure of organs such as the kidneys. Some Ebola hemorrhagic fevers have resulted in death rates of close to 90 percent of infected patients, while others have been as low as 20 percent. Similarly, incubation periods vary for the different diseases, from only a few days for some diseases to as long as three weeks for others. The best-known hemorrhagic fever, Ebola, has an incubation period of two to twenty-one days.

Treatment and Therapy

Treatment for viral hemorrhagic fever varies from disease to disease. In many cases, the only care that can be given is that of relieving the suffering of the patient by treating the symptoms—giving liquids intravenously to replace fluids lost through vomiting or diarrhea, trying to keep electrolytes balanced, and giving drugs that may reduce the patient’s fever or body aches. In some cases, patients have been successfully treated with blood transfusions from persons who have survived a similar illness.

Because the exact transmission routes for many hemorrhagic fevers remain unclear, once patients are diagnosed, a strict quarantine must be instituted, with health care workers and family members alike wearing protective clothing to prevent becoming contaminated with any infectious material. When a patient dies, the body must also be handled carefully. In the case of Ebola, the World Health Organization (WHO) recommends burial or cremation as quickly as possible following death.

Perspective and Prospects

As the population has expanded globally and humans have encroached upon formerly isolated wildlife habitats, more viral hemorrhagic fevers have been discovered, sometimes through the case of just one or two persons becoming infected by a previously unknown pathogen and sometimes through devastating outbreaks resulting in many deaths. Despite many years of research, many of these diseases still remain scientific mysteries.

The best-known example, Ebola hemorrhagic fever virus, exists in multiple locations in Africa. Some strains are comparatively mild; some are extremely virulent, spreading quickly and causing high numbers of deaths within a population. Researchers now know that, as is true with many viruses, patients who have been infected by Ebola and survive retain antibodies to that strain of virus for decades. They do not yet know if that means those people are effectively immune to Ebola.

Theoretically, it should be possible to develop vaccines against the viral hemorrhagic diseases, but several factors mitigate such work. First is the reality that although many can be quite devastating in terms of death rates, outbreaks that have occurred to date have been in remote areas or have affected very low numbers of persons. It is easy to argue for funding vaccine research work when a disease is widespread, as in the historical example of polio; it becomes much more difficult for researchers when the disease in question is localized in a nonindustrialized country such as the Sudan or Uganda. In recent years, the threat of viruses such as Ebola being utilized for bioterrorism, however, has led to more effort being put into finding effective vaccines and treatments, but for most of the viral hemorrhagic diseases any vaccines or treatments developed to date remain classified as experimental.

Bibliography

"Ebola Haemorrhagic Fever." World Health Organization, Aug. 2012.

"Hemorrhagic Fevers." MedlinePlus, May 20, 2013.

"Haemorrhagic Fevers, Viral." World Health Organization, Jan. 2013.

Hewlitt, Barry S., and Bonnie L. Hewitt. Ebola, Culture, and Politics: The Anthropology of an Emerging Disease. Belmont, Calif.: Thomson Higher Education, 2008.

Shors, Teri. Understanding Viruses. 2d ed. Sudbury, Mass.: Jones and Bartlett, 2013.

Strauss, James H., and Ellen G. Strauss. Viruses and Human Disease. 2d ed. San Diego, Calif.: Academic Press, 2008.

"Viral Hemorrhagic Fevers." Centers for Disease Control and Prevention, Nov. 22, 2011.