Viral haemorrhagic fevers: origins, reservoirs, transmission and guidelines
Examples of viral haemorrhagic fevers (VHFs) include Lassa fever, Crimean-Congo haemorrhagic fever, Marburg and Ebola virus diseases.
Viral haemorrhagic fevers are a group of illnesses caused by several distinct families of viruses: arenaviruses, filoviruses, bunyaviruses and flaviviruses.
Some of these cause relatively mild illnesses, whilst others can cause severe, life-threatening disease; some are high consequence infectious diseases (HCIDs).
The viruses depend on their animal hosts for survival, so they are usually restricted to the geographical area inhabited by those animals.
The viruses are endemic in areas of Africa, South America and Asia, with some present in parts of Europe.
Arenaviruses
Arenaviruses belong to the order Hareavirales, within the class Bunyaviricetes.
The arenaviruses which cause infection in humans are divided into Old World mammarenaviruses, referring to those found in the African continent, and the New World mammarenaviruses, referring to those found in South America. Most of the arenaviruses are associated with a primary rodent reservoir species, although some can infect more than one rodent species. Humans are usually infected through mucosal exposure, aerosolised excretions or secretions, or by direct contact of broken skin with infectious material from infected rodents.
Old World Mammarenaviruses
This group includes
- Lassa virus: the cause of Lassa fever, endemic in parts of west Africa. Lassa virus has caused outbreaks in Nigeria, Liberia, Guinea, Sierra Leone, and is found in several other West African countries.
- Lujo virus: a novel virus that caused a small outbreak in South Africa originating from a case imported from Zambia in 2008.
Lassa fever and Lujo virus disease are designated as HCIDs in the UK.
New World Mammarenaviruses
This group includes the following:
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Junin virus: cause of Argentinian haemorrhagic fever
- Machupo virus: cause of VHF in Bolivia
- Chapare virus: cause VHF in Bolivia
- Guanarito virus: cause of Venezuelan haemorrhagic fever
- Sabia virus: cause of Brazilian haemorrhagic fever
These viruses are often geographically limited to where the primary rodent reservoir is found. Junin and Machupo virus are designated as HCIDs in the UK.
Other viruses within the class Bunyaviricetes
In addition to arenaviruses, other viruses within the class Bunyaviricetes may cause disease in humans. This group includes
- Crimean-Congo haemorrhagic fever (CCHF) virus: cause of CCHF. This is found in many countries across Europe, the African continent and Asia. Transmission is via contact with infected animals (usually through slaughter or butchering), or a bite from an infected Hyalomma tick. Person to person transmission has also been described. CCHF is designated as an HCID in the UK.
- Hantaviruses: several viruses which can cause haemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome including Andes virus, which is designated as an HCID in the UK. Transmission is usually through exposure to infected rodents or their excreta.
- Rift Valley fever virus: cause of Rift Valley fever. This can be transmitted from direct contact with infection animals (usually through slaughter or butchering), ingestion of products from infected animals, or through a bite from an infected mosquito.
Filoviruses
Filoviruses can cause severe illness in humans. The two groups known to cause infection in humans are:
- Marburg virus: cause of Marburg disease (MARD). The Egyptian rousette bat (Rousettus aegyptiacus), is considered to be the natural host for Marburg virus.
- Orthoebolaviruses: cause of Ebola disease (EBOD). There are several species causing disease in humans. Ebola (Zaire) virus and Sudan virus have caused significant outbreaks in humans. Fruit bats from the Pteropodidae family are believed to be the natural reservoir.
Human to human transmission can occur for both Marburg disease and Ebola disease and they are designated as HCIDs in the UK.
Flaviviruses
Flaviviruses are found throughout the world and are primarily spread by mosquitoes and ticks. Human to human transmission does not occur, except via transfusion, transplantation or sharps injuries. Flaviruses which can cause a viral haemorrhagic fever syndrome include:
- Alkhurma virus: cause of Alkhurma haemorrhagic fever, primarily found in Saudi Arabia. Transmission is via contact with infected animals (such as camels) or through the bite of an infected tick.
- Dengue virus: the cause of dengue haemorrhagic fever and dengue fever. Dengue virus is widespread across the world. Transmission is through the bite of an infected Aedes mosquito.
- Kyasanur Forest virus: cause of Kyasanur Forest disease, primarily found in Karnataka state, India. Transmission is via the bite of an infected tick, and occasionally through contact with an infected animal.
- Omsk virus: cause of Omsk haemorrhagic fever, primarily found in Siberia. Transmission is via contact with the excreta of infected rodents, or through the bite of an infected tick.
- Yellow fever virus: the cause of yellow fever
None of the flaviviruses are designated as HCIDs.
Guidelines
The UK has specialist guidance on the management (including infection prevention and control) of patients with HCID VHFs. It provides advice on how patients suspected of being infected with a VHF designated as a HCID should be comprehensively assessed, rapidly diagnosed and safely managed within the NHS, to ensure the protection of public health. Infection services can also contact the Imported Fever Service (IFS) for advice on risk assessment, testing and clinical advice.
The Rare and Imported Pathogens Laboratory (RIPL) provides diagnostic services for both the HCID and non-HCID VHFs. Advice from RIPL clinicians can be obtained via the IFS.
Prevention
For haemorrhagic fever viruses that can be transmitted from human-to-human, great care needs to be taken when caring for patients to avoid contact with infected bodily fluids. Patients should be isolated, and strict barrier nursing techniques should be used, including PPE as described in guidance for the management of VHFs.
HCID VHFs in the UK
Environmental conditions in England and Wales do not currently support the natural reservoirs of infection, and cases do not occur here except those linked to travel or travel associated. For the HCID VHFs, there have been:
- 16 cases of Lassa fever reported in the UK since 1971
- 2 confirmed cases of CCHF (1 in 2012 and 1 in 2014)
- 4 cases of EBOD reported in the UK since 1976: One was a laboratory-acquired case in 1976 and 3 cases were in healthcare workers associated with the West African epidemic 2014 to 2015.
Updates to this page
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Page has been updated and revamped to reflect the latest information available about the pathogens that cause viral haemorrhagic fevers.
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Updated page with epidemiological maps.
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Updated the VHFs in Africa map.
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The Viral haemorrhagic fevers in Africa: areas of known risk map has been updated.
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Updated 'Viral haemorrhagic fevers in Africa: areas of known risk map (JPG image)'.
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First published.