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Hemorrhagic Fevers

Including Ebola virus disease, Marburg virus disease, Lassa fever, and other viral causes.

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Reporting Obligations

Individuals who have or may have hemorrhagic fever shall be reported as soon as possible to the local Health Unit. Suspected cases of Ebola Virus Disease (EVD) require activation of the Canadian Viral Haemorrhagic Fever Contingency Plan.

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Aetiologic Agent

Viruses from several families can cause viral hemorrhagic fever (VHF). Members of the Filoviridae family, the Ebola and Marburg viruses, are antigenically distinct, and cause VHF. In Africa, 4 different subtypes of the Ebola virus have been associated with human illness. Members of other viral families causing VHF include bunyaviruses (i.e. hantaviruses), arenaviruses (i.e. Lassa virus) and flaviviruses (i.e. Yellow Fever virus, Dengue virus).

Clinical Presentation

Viral hemorrhagic fevers are associated with an acute onset of fever, severe illness and hemorrhagic symptoms including hemorrhagic or purpuric rash, epistaxis, hematemesis, hemoptysis, blood in stool and other hemorrhagic symptoms.

In the case of dengue fever, clinical presentation is mild in comparison to dengue hemorrhagic fever including fever, headache, myalgia, nausea and vomiting. Whereas cases of dengue hemorrhagic fever are reportable, cases of dengue fever without identified hemorrhagic manifestations are not reportable.

In cases of Lassa fever about 80% of human infections are mild or asymptomatic and the remaining have severe multisystem disease. Patients present with malaise, fever, headache, sore throat, cough, nausea, vomiting, diarrhea, myalgia, and chest and abdominal pain.

Modes of Transmission

For Ebola and Marburg, person to person transmission occurs by direct contact with infected blood, secretions organs or semen. Risk is highest during the late stages of illness when the infected person is vomiting, having diarrhea or haemorrhaging and post-mortem contact with bodily fluids. Risk during the incubation period is low.

Nosocomial infections have been frequent; virtually all ebola (Zaire, now Democratic Republic of Congo) patients who acquired infection from contaminated syringes and needles have died.

For dengue hemorrhagic fever, no direct person to person spread; persons are infective for mosquitoes from shortly before the febrile period to the end thereof, usually 3–5 days.

For Lassa fever, primarily through aerosol or direct contact with excreta of infected rodents deposited on surfaces such as floors, beds or in food and water. It can also be spread person to person through sexual contact and in hospitals from infected persons’ pharyngeal secretions, blood, or urine or from contaminated needles, or in laboratory accidents.

Incubation Period

Ebola and Marburg virus diseases: Probably 5 to 15 days.

Dengue: From 3 to 14 days, commonly 4 to 7 days.

Lassa: Commonly 6 to 21 days.

Period of Communicability

Ebola and marburg are communicable as long as blood and secretions contain virus. For dengue hemorrhagic fever, the mosquito becomes infective 8–12 days after the viraemic blood-meal and remains so for life. There is no person-person transmission of dengue. For Lassa fever, person to person spread may theoretically occur during the acute febrile phase when virus is present in secretions and excretions. Virus can be excreted in urine for 3–9 weeks from onset of illness and can be spread by sexual contact through semen for up to 3 months after infection.

Risk Factors/Susceptibility

All ages are susceptible. Recovery from infection with one dengue virus serotype provides lifelong homologous immunity but only short-term protection against other serotypes and may exacerbate disease upon subsequent infections potentially leading to Dengue Hemorrhagic Fever (as opposed to Dengue Fever).

Diagnosis and Laboratory Testing

Accepted testing for diagnosis is via viral culture, NAAT, Antigen detection, IgG and IgM serology.

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Treatment and Case Management

Clinical management of VHF and Dengue Hemorrhagic Fever (DHF), in the latter especially if complicated by dengue shock syndrome, would be the responsibility of medical specialists such as an infectious disease specialist.

Contacts of DHF are not at risk, given the absence of person to person transmission. Given the severity and rarity of hemorrhagic fevers, a single confirmed case constitutes an outbreak.

Additional Resources

Public Health Ontario. “Ebola virus disease (EVD), 2016.”

Public Health Agency of Canada. “Viral Haemorrhagic Fever.”

Public Health Agency of Canada. “Fever in the Returning International Traveller Initial Assessment Guidelines, CCDR, 2011”. (This resource is archived but still current and can be accessed from this link)

Government of Canada. “Ebola Virus Disease”.


Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2022.