AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Background

Viral hemorrhagic fevers (VHFs) are a group of febrile illnesses caused by RNA viruses from several viral families. These highly infectious viruses lead to a potentially lethal disease syndrome characterized by fever, malaise, vomiting, mucosal and gastrointestinal (GI) bleeding, edema, and hypotension. The 4 viral families known to cause VHF disease in humans include the Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae. General characteristics of these viral families can be found in the table below.

Table 1. Viral Families Causing Viral Hemorrhagic Fever

Arenaviridae

Arenaviridae are spread to humans by rodent contact and include Lassa virus in Africa and several rare South American hemorrhagic fevers such as Machupo, Junin, Guanarito, and Sabia. Lassa virus is the most clinically significant of the Arenaviridae, accounting for serious morbidity and mortality in West Africa.

Lassa fever first appeared in Lassa, Nigeria, in 1969. It has been found in all countries of West Africa and is a significant public health problem in endemic areas. In populations studied, Lassa fever accounts for 5-14% of hospitalized febrile illnesses. Its natural reservoir is a small rodent whose virus-containing excreta is the source of transmission.

Bunyaviridae

This group includes Rift Valley fever (RVF) virus, Crimean-Congo hemorrhagic fever (CCHF) virus, and several hantaviruses. The RVF and CCHF viruses are both arthropod-borne viruses. RVF virus, an important African pathogen, is transmitted to humans and livestock by mosquitos and by the slaughter of infected livestock. CCHF virus is carried by ticks and causes a fulminant, highly pathogenic form of VHF notable for aerosol transmission of infective particles. Outbreaks of CCHF have occurred in Africa, Asia, and Europe.

Many hantaviruses are spread worldwide, causing 2 major syndromes: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). They are divided into Old World hantaviruses (such as the prototypical Hantaan virus of Korea), which generally cause HFRS, and New World hantaviruses, causing HPS. Rodents carry both types. A previously undiscovered Hantavirus, Sin Nombre virus, was the cause of an outbreak of highly lethal HPS in the southwestern US in 1993.

Filoviridae

The most notorious of the VHF viruses, including Ebola and Marburg viruses, belong to the Filoviridae family. Ebola virus first was described in 1976 after outbreaks of a febrile, rapidly fatal hemorrhagic illness were reported along the Ebola River in Zaire (now the Democratic Republic of the Congo) and Sudan. Sporadic outbreaks have continued since that time, usually in isolated areas of central Africa. An outbreak in Kikwit, Zaire, in 1995 led to 317 confirmed cases, with an 81% mortality rate. Two thirds of the patients were among health care workers caring for infected individuals. An outbreak in Uganda in late 2000 resulted in 425 cases and claimed 225 lives. In September 2007, the cause of an ongoing VHF outbreak in the Congo was identified as Ebola. Ebola has 4 distinct subtypes: Ebola-Zaire, Ebola-Sudan, Ebola-Ivory Coast, and Ebola-Reston, a form that causes illness only in nonhuman primates.

The natural reservoir of Ebola virus remains unknown, although some recent studies have suggested that bats may be a potential reservoir for Ebola.

Marburg virus, named after the German town where it first was reported in 1967, is another highly pathogenic member of the Filoviridae family that is traced to central Africa. As in Ebola, the natural host for the virus is unknown. Marburg virus was contracted by a traveler to central Africa in 1987 and has been endemic since 1998 in Durba, Democratic Republic of the Congo, and in persons exposed in gold mines. Marburg virus was determined to be the causative agent in a 2004-2005 outbreak of hemorrhagic fever in Angola that led to 252 confirmed cases and 227 deaths (90% case-fatality rate).

Flaviviridae

Yellow fever and dengue fever are the most well known diseases caused by flaviviruses. Both are mosquito-borne; yellow fever is found in tropical Africa and South America, and dengue fever is found in Asia, Africa, and the Americas. They are notable for their significant effect on prior military campaigns and their continued presence throughout endemic areas.

Pathophysiology

The primary defect in patients with VHF is that of increased vascular permeability. Hemorrhagic fever viruses have an affinity for the vascular system, leading initially to signs such as flushing, conjunctival injection, and petechial hemorrhages, usually associated with fever and myalgias. Later, frank mucous membrane hemorrhage may occur, with accompanying hypotension, shock, and circulatory collapse. The relative severity of the clinical presentation may vary depending on the virus in question, amount, and route of exposure.

In acute disease, patients are extremely viremic, and messenger ribonucleic acid (mRNA) evidence of multiple cytokine activation exists. In vitro studies reveal these cytokines lead to shock and increased vascular permeability, the basic pathophysiologic processes most often seen in VHF infection. Another prominent pathologic feature is pronounced macrophage involvement. Inadequate or delayed immune response to these novel viral antigens may lead to rapid development of overwhelming viremia. Extensive infection and necrosis of affected organs also are described. Hemorrhagic complications are multifactorial and are related to hepatic damage, consumptive coagulopathy, and primary marrow injury to megakaryocytes. Aerosol transmission of some VHF infections is reported among nonhuman primates and likely is a mode of transmission in patients with severe infection.

Multisystem organ failure affecting the hematopoietic, neurologic, and pulmonary systems often accompanies the vascular involvement. Hepatic involvement varies with the infecting organism and is at times seen with Ebola, Marburg, RVF, CCHF, and yellow fever. Renal failure with oliguria is a prominent feature of HFRS seen in Hantavirus infection and may be seen in other VHFs as intravascular volume depletion becomes more pronounced. Bleeding complications are particularly prominent with Ebola, Marburg, CCHF, and the South American arenaviruses.

Frequency

United States

Cases of VHF in the US are extremely rare and usually are found in patients who recently have visited endemic areas or among those with potential occupational exposure to hemorrhagic fever viruses. Lassa fever has been reported in the US in travelers from West Africa and was most recently reported in the US in August 2004. In 1994, a virologist working with Sabia, a Brazilian HF virus, accidentally contracted the disease. No human cases of Ebola or Marburg virus disease have been reported in the US. In 1989, an outbreak of hemorrhagic fever among imported macaque monkeys in Reston, Virginia, led to the discovery of Ebola-Reston, a variant of Ebola virus that originated in the Philippines and does not cause disease in humans.

International

Lassa fever is responsible for an estimated 100,000-300,000 infections per year, with 5,000 deaths. Cases have been reported throughout West Africa, particularly in Nigeria, Sierra Leone, Guinea, and Liberia. Other arenaviruses are responsible for sporadic VHF outbreaks throughout South America.

RVF and CCHF are responsible for intermittent epidemics in Africa (for RVF) and in areas of Africa, Asia, and Europe (for CCHF). HFRS due to Hantavirus infection continues to be an ongoing health concern, particularly in Asia, affecting up to 200,000 patients annually.

Ebola virus appears sporadically in endemic areas of the former Zaire and Sudan. Ebola virus also has been reported in Gabon, the Ivory Coast, and Uganda. Outbreaks appear to propagate in hospital settings, often involving health care providers.

Yellow fever continues to be a serious problem in tropical areas of South America and Africa, where vaccination is not widespread. The World Health Organization estimates that approximately 200,000 cases per year occur in Africa. Dengue HF is endemic in Southeast Asia, and more than 1 million cases occur annually.

Mortality/Morbidity

Case-fatality rates of patients with VHF vary from less than 10% (eg, in dengue HF) to approximately 90%, as has been reported in patients with Ebola-Zaire and the recent Angola Marburg outbreak. The most recent outbreak of Ebola-Sudan in Uganda had a 50% case-fatality rate.

Complications from VHF infection include retinitis, orchitis, hepatitis, transverse myelitis, and uveitis. In patients who recover from Lassa fever infection, deafness is the most common complication. Spontaneous abortion also is common. Renal insufficiency is associated with HFRS infection.

Race

No racial predilection has been identified, although cases have originated in African areas.

Sex

No predilection for either sex has been identified.

Age

VHF affects all ages according to exposure and local demographics.

CLINICAL

Section 3 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

History

• Obtain a detailed travel history, paying particular attention to recent travel to tropical or rural areas, such as Central or South America (yellow fever, arenaviruses), West Africa (Lassa fever), or to endemic portions of Central Africa (Ebola, Marburg, RVF, CCHF). Ask about contact with potential arthropod or rodent reservoirs.
• • Since the natural reservoir for Ebola and Marburg viruses is unknown, contact with infected monkeys or humans is not a prerequisite for transmission of infection.
  • Direct contact with rodents infected with hemorrhagic fever viruses (eg, arenaviruses, hantaviruses) is not necessary for transmission of infection, since aerosolized excreta may transmit infection.
• Contacts of patients with known VHF, especially family members or health care workers caring for infected patients, are at risk for infection if appropriate barrier precautions are not used.
• • Transmission of VHF has occurred from the reuse of unsterile needles and syringes used for treatment of infected patients.
  • Transmission of VHF also has occurred to individuals handling the deceased in preparation for burial or to individuals involved in the slaughter of infected livestock (as in RVF or CCHF).
• Because of their extreme pathogenicity and potential for transmission by fine particle aerosol, VHF viruses are considered potential biological warfare agents. In addition, Dr Ken Alibek, the former Deputy Director of the once massive Soviet bioweapons program, Biopreparat, claims Soviet scientists successfully had produced a stable Marburg virus biological weapon that could be delivered as an aerosol.
• • Large numbers of military personnel with VHF symptoms suggest such an attack.
  • An outbreak of VHF in a nonendemic area also suggests a biological warfare attack.
• Incubation periods for VHF vary from 2-21 days.
• The initial symptoms correspond to development of viremia and include the following:
• • High fever
  • Headache
  • Fatigue
  • Abdominal pain
  • Myalgias
  • Prostration
• In more advanced disease, signs and symptoms include the following:
• • Hematemesis and bloody diarrhea
  • Generalized mucous membrane hemorrhage
  • Rash
  • Altered mental status and cardiovascular collapse (preterminal events)

Physical

Depending on the progress of the disease, patients with VHF initially may present with minimal signs, suggesting a more benign viral syndrome. Maintain a high index of suspicion. As the disease progresses, more classic findings are present as follows:

• Fever
• Pharyngitis
• Conjunctival injection
• Nondependent edema
• Petechial or ecchymotic rash
• GI bleeding
• Hypotension and/or shock
• Most hemorrhagic fevers, except Rift Valley Fever, can produce a variety of cutaneous findings that are principally caused by vascular instability and bleeding abnormalities. Such findings include flushing, petechiae, purpura, ecchymoses, and edema.
• The Old World arenavirus causing Lassa fever results in the greatest amount of edema of any of the hemorrhagic fever viruses. Additionally, no bleeding abnormalities are present.
• The New World arenaviruses (Junin, Machupo, Sabia, and Guanarito) cause less edema and variable amounts of petechiae, purpura, ecchymoses, palatal hyperemia, and mucosal hemorrhage.
• The most severe hemorrhage from a hemorrhagic fever virus follows infection with the Congo Crimean Hemorrhagic Fever virus.
• Hantaviruses can cause a relatively distinctive eruption with a petechial eruption around the neck and on the anterior and posterior axillary folds, arms, and trunk. A sunburn-like flush is seen on the head, neck, and upper chest and back and may be accompanied by facial edema. Sometimes, a morbilliform eruption occurs. Oral and conjunctival surfaces may develop severe hemorrhages.
• The greatly feared filoviruses (Marburg and Ebola) exhibit characteristic exanthems that are best seen in fair-skinned patients. Soft palatal hyperemia accompanies the flu-like prodrome and is followed between days 5 and 7 by a nonpruritic, centripetal, pinhead-sized papular, erythematous exanthem. Within 24 hours, this can develop into large and coalescent, well-demarcated, sometimes hemorrhagic macules and papules. In severe cases, hemorrhage exudes from mucous membranes, venipuncture sites, and body orifices.
• Dengue virus causes a characteristic erythematous exanthem with striking islands of sparing.

Causes

• See Table 1.

DIFFERENTIALS

Section 4 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Other Problems to be Considered

Typhoid fever
Shigellosis
Meningococcemia
Rickettsial infections
Acute leukemia
Idiopathic or thrombotic thrombocytopenic purpura

WORKUP

Section 5 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Lab Studies

• Because of risks associated with handling infectious materials, perform the minimum necessary laboratory testing for diagnostic evaluation and patient care.
• A complete blood count often indicates leukopenia and thrombocytopenia. These findings may not be present in Lassa fever.
• Elevated hepatic transaminases are observed in VHF and are predictive of high mortality in Lassa fever infection.
• Prothrombin time, activated partial thromboplastin time, international normalized ratio, and clotting times are prolonged.
• A disseminated intravascular coagulation profile including fibrinogen level, fibrin degradation products, and platelet count may be useful.

Other Tests

• Most patients are viremic at the time of presentation (Hantavirus is an exception). Specific viral diagnosis can be made using serologic tests, including enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction. Difficult cases may require tissue cultures. During the 2000-2001 Ebola outbreak in Uganda, reverse transcriptase-PCR (RT-PCR) emerged as a very effective means for detecting Ebola virus in patient serum, plasma, and whole blood.
• • Because of the need for specialized microbiologic containment and handling of these viruses, initiate contact with the Centers for Disease Control and Prevention (CDC; Atlanta, GA) as soon as possible and prior to transport of specimens for virus-specific diagnosis. Specific state and federal statutes govern the shipment of highly infectious disease agents.
  • The CDC and the US Army Medical Research Institute for Infectious Diseases (USAMRIID; Frederick, MD) are among the 8 Biosafety Level 4 (BSL-4) laboratory facilities in the US with such diagnostic facilities. At least 7 more are under construction.
• Report all suspected cases of VHF immediately to local and state public health departments and to the CDC.

TREATMENT

Section 6 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Prehospital Care

Supportive care is based on the patient's physiologic condition. Because most patients requiring prehospital evaluation and transport are in the early stages of the disease, universal precautions should be adequate. In patients with respiratory symptoms (eg, cough, rhinitis), use face shields and high-efficiency particulate air (HEPA) filter masks.

Emergency Department Care

• Fluid resuscitation and supportive care are the mainstays of emergency department therapy. Intravenous crystalloids, oxygen, and cardiac monitoring are the most appropriate initial steps in the treatment of patients in whom VHF is suggested.
• Administer blood and blood products as clinically indicated.
• Avoid intramuscular injections and the use of aspirin or other anticoagulants.
• Minimize invasive procedures because of the risk associated with viral transmission from sharp objects.
• Place patients in a private room.
• • A negative pressure room is not necessary during early stages of the disease but may be necessary if patients have prominent cough, vomiting, diarrhea, or hemorrhage.
  • Prevent nonessential staff and visitors from entering the room.
• All staff entering the room should wear gloves and gowns.
• Persons coming within 3 feet of the patient should wear face shields or surgical masks with eye protection (including side shields). Use HEPA filter masks if patients have prominent respiratory, GI, or hemorrhagic symptoms.
• If large amounts of blood or other body fluids are present in the environment, use leg and shoe coverings.
• Before exiting the room, discard all used protective barriers and clean shoes with a hospital disinfectant or solution of household bleach. If possible, use an anteroom for putting on and removing protective barriers and for storing supplies.

MEDICATION

Section 7 of 12  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

No specific antiviral therapy is available for Ebola or Marburg virus infection. The use of convalescent serum (ie, sera from patients who have survived infection) is suggested as a possible therapy. Late during the 1995 Kikwit, Zaire, outbreak, 8 Ebola patients received blood transfusions from Ebola survivors. Of these, 7 survived. However, no clear evidence exists that links their survival directly to this therapy.

Lassa fever and HFRS due to Hantavirus infection have been treated effectively with IV and oral ribavirin. Because of this, ribavirin has been recommended as a potential treatment for other arenaviruses and bunyaviruses. Treatment is most effective when given early in the clinical course. Ribavirin also is recommended for postexposure prophylaxis.

Development of a Lassa virus vaccine is continuing at CDC. Yellow fever vaccine is readily available and is both safe and effective. Argentine HF (Junin) vaccine is also effective and may protect against Bolivian HF as well. RVF and Hantaan (HFRS) vaccines are also available. In 2000, a vaccine demonstrated effectiveness against Ebola virus in nonhuman primates. No human vaccine, however, is available, although research is ongoing. Recent efforts have focused on postexposure prophylaxis for filovirus exposure and have achieved success using a primate model.

Drug Category: Antivirals

The goals in the use of antivirals are to shorten the clinical course, prevent complications, prevent the development of latency and/or subsequent recurrences, decrease transmission, and eliminate established latency.

FOLLOW-UP

Section 8 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Further Inpatient Care

• Hospitalize patients with suspected or confirmed VHF infection because of the significant risk for nosocomial spread of the infection.
• Notification of local and state public health departments and CDC may provide resources for further epidemiologic investigation into the source of the infection.
• Appropriate barrier precautions should remain in place throughout the hospital course because of the highly pathogenic nature of VHF infection and because various causes of VHF often are clinically indistinguishable.

Deterrence/Prevention

• As the natural reservoirs for Ebola and Marburg virus infection remain unknown, no specific prevention measures are established.
• Efforts are underway in West Africa to educate people in high-risk areas about ways to decrease rodent populations, thereby reducing transmission of Lassa fever.
• Strict barrier precautions in the treatment of patients with known or suspected VHF infection reduce nosocomial transmission.

Complications

• Complications from VHF infection include retinitis, orchitis, encephalitis, hepatitis, transverse myelitis, and uveitis.
• In patients who recover from Lassa fever infection, deafness is the most common complication. Spontaneous abortion also is common.
• Renal insufficiency is associated with HFRS infection.

Patient Education

• For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center. Also, see eMedicine's patient education articles Biological Warfare and Personal Protective Equipment.

MISCELLANEOUS

Section 9 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Medical/Legal Pitfalls

• Failure to admit patients for supportive therapy and definitive diagnosis
• Failure to maintain appropriate isolation precautions or failure to prevent unnecessary patient-staff contacts
• Failure to exclude other possible diagnoses that may require specific therapies

Special Concerns

• For more information, see CDC Fact Sheets on VHF.

ACKNOWLEDGMENTS

Section 10 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Thomas W McGovern, MD, to the development and writing of this article.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

Media file 1:  Ebola virus. Electron micrograph courtesy of the Centers for Disease Control and Prevention.
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Media file 2:  Marburg virus. Negative stain image courtesy of the Centers for Disease Control and Prevention.
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Media file 3:  Mastomys rodent, natural host of Lassa virus. Image courtesy of the Centers for Disease Control and Prevention.
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Media file 4:  Bunyavirus infection. Ecchymoses encompassing left upper extremity one week after onset of CCHF. Ecchymoses often are accompanied by hemorrhage in other locations: epistaxis, puncture sites, hematemesis, melena, and hematuria. Image provided by Robert Swaneopoel, PhD, DTVM, MRCVS, National Institute of Virology, Sandringham, South Africa.
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Media file 5:  Apodemus agrarius, the vector of Korean hemorrhagic fever caused by a hantavirus. Photo courtesy of David McClain, MD.
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Media file 6:  Bunyavirus infection - Hantaan virus. Patient with Korean hemorrhagic fever caused by Hantaan virus demonstrating typical 'sunburn flush' of cheeks, chin, and base of neck. Photo courtesy of John Huggins, PhD.
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Media file 7:  Bunyavirus infection. A patient with Korean hemorrhagic fever demonstrating conjunctival hemorrhages, facial petechiae, and "sunburn flush" of the cheeks. Photo courtesy of John Huggins, PhD.
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Media file 8:  Filovirus disease - Ebola fever. Patient with Ebola hemorrhagic fever during 1976 outbreak in Zaire demonstrating palatal petechiae and hemorrhage. Photo courtesy of Joel Breman.
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Media file 9:  Patient with morbilliform exanthem of dengue fever. Note islands of sparing characteristics for dengue. Photo courtesy Duane Gubler, PhD.
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Media file 10:  Patient with dengue hemorrhagic fever complicated by ecchymoses. Photo courtesy of Duane Gubler, PhD.
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REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• Multimedia
• References

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Article Last Updated: Nov 19, 2007