Viral Haemorrhagic Fevers

Unique identifier / Notation

BI0109

Synonyms

VHF

Viral haemorrhagic fevers include a spectrum of relatively mild to severe life-threatening diseases characterized by sudden onset of muscle and joint pain, fever, bleeding and shock from loss of blood. In severe cases, one of the most prominent symptoms is bleeding, or haemorrhaging, from orifices and internal organs (WHO, no date a).

Primary reference(s)

WHO, no date a. Haemorrhagic fevers: Viral. World Health Organization (WHO). Accessed 18 February 2025.

Annotations

Additional scientific description

Viral haemorrhagic fevers (VHF) include a spectrum of relatively mild to severe life-threatening diseases characterized by sudden onset of muscle and joint pain, fever, bleeding and shock from loss of blood. In severe cases, one of the most prominent symptoms is bleeding, or haemorrhaging, from orifices and internal organs (WHO, no date a).

VHF are associated with the occurrence of major epidemics with high case-fatality rates owing to the fact that there are no specific medical countermeasures such as vaccines or antivirals, the exception being yellow fever. Lack of timely laboratory diagnosis, late detection, inadequate infection control practices at health care facilities, and weak vector control programmes could also prolong outbreaks of haemorrhagic fevers.

Viral haemorrhagic fever (VHF) diseases are caused by 3 families (Arenaviridae, Filoviridae, Flaviviridae) and 1 order (Bunyavirales) of enveloped RNA viruses (CDC, 2024). Most VHFs fall into one of four families of virus:

Arenaviruses - Each arenavirus has one or a few closely related rodents that carry the virus without getting sick themselves. This is known as the reservoir, or source of the virus in nature. The reservoir can spread the virus to people through infected urine, saliva, or droppings, and can cause severe disease in people. People are infected with arenaviruses by:
- Touching with rodent urine, droppings, or nesting materials from an infected rodent
- Breathing in air contaminated by rodent urine, droppings or nesting materials.
- Being bitten or scratched by an infected rodent.
- Eating food contaminated by urine, droppings, or saliva from an infected rodent.
- Contact with another person who has certain arenaviruses, such as Chapare, Lassa, Machupo, and Lujo viruses. (CDC, 2024).
Bunyavirales order - Viruses in the Bunyavirales order are spread by rodents or insects, such as mosquitos, ticks, or sand flies. They can produce mild to severe disease in animals and people. Many of these viruses cannot spread between people. However, person -to person spread of Crimean-Congo haemorrhagic fever has occurred in healthcare settings where infection control was limited (CDC, 2024).
Filoviruses can cause severe illness in people and nonhuman primates (such as monkeys and gorillas). The Egyptian rousette bat, Rousettus aegyptiacus, is a cave-dwelling bat, and the reservoir for Marburg virus. Bats infected with orthomarburg viruses do not show obvious signs of illness. It's not known what animal carries ebolaviruses in nature, but scientists suspect that bats are likely involved. Once filoviruses are introduced into the human population, they can spread between people through contact with an infected person's body fluids. Caretakers and healthcare providers who do not use appropriate personal protective equipment (PPE) are at higher risk of infection (CDC, 2024).
Flaviviruses are found throughout the world. These viruses, which are primarily spread by mosquitoes and ticks, can cause mild to severe disease or even death. They can also cause disease in animals, creating a large economic and social impact on people living in affected areas (CDC, 2024).
Paramyxoviruses can cause sudden onset of respiratory disease. While there are many viruses included within the Paramyxoviridae family, Hendra and Nipah viruses are considered more serious because they require a specialized lab, (biosafety level 4 lab) and can cause serious disease, spread between animals and people, and have no vaccine or treatment currently available (CDC, 2024),

Most VHFs fall into one of four families of virus:

Arenavirus (order Bunyavirales)

Lassa fever virus (BI0215)
Lujo virus
Junin virus
Chapare virus
Sabia virus
Machupo virus
Guanarito virus

Filoviruses

Ebola virus (EBOV) (BI0209)
Sudan virus (SUDV)
Bundibugyo virus (BDBV)
Taï Forest virus (TAFV)
Marburg virus (MARV) (BI0220)
Ravn virus

Flavirviruses

Alkhurma hemorrhagic fever virus
Kyasanur Forest Disease virus
Omsk Hemorrhagic Fever virus
Dengue virus (BI0207)
Yellow Fever virus (BI0241)

Bunyavirales order

Hantavirus (Bunyavirales) Hantaviruses
Nairovirus (order Bunyavirales) Crimean-Congo Haemorrhagic Fever virus (BI0206)
Phenuvirus (Bunyavirales) Rift Valley Fever virus (BI0311)

Paramyxoviruses

Hendra virus
Nipah virus (CDC, 2024)

Several viral haemorrhagic fevers are prone to outbreaks and epidemics with high case fatality rates. These include Ebola, Lassa fever and Crimean-Congo haemorrhagic fever. These diseases are part of the priority list for the World Health Organization (WHO) WHO research and development (R&D) Blueprint for Epidemics (WHO, 2024).

Metrics and numeric limits

The WHO Global Clinical Platform aims to understand the clinical features, prognostic factors and outcomes from viral haemorrhagic fever, focussing on filovirus infection. Data contributed to the platform helps WHO to support member states in understanding the health problems from national and international perspectives. Health care facilities/collaborators around the world have contributed clinical data to the WHO Clinical Data Platform. (WHO, no date b; WHO, no date c)

Key relevant UN convention / multilateral treaty

International Health Regulations (2005), 3rd ed. (WHO, 2016b).

Drivers

Viral haemorrhagic fevers occur widely in tropical and subtropical regions (WHO, no date). Most of them have a non-human natural reservoir, with some transmitted by mosquitoes or ticks. A small number are preventable by vaccine (e.g., yellow fever) and others have potential vaccines and treatments in different stages of development (WHO, no date a).

Impacts

VHF are associated with the occurrence of major epidemics with high case-fatality rates, owing to the fact that there are no specific medical countermeasures such as vaccines or antivirals, the exception being yellow fever. Lack of timely laboratory diagnosis, late detection, inadequate infection control practices at health care facilities, and weak vector control programmes could also prolong outbreaks of haemorrhagic fevers. (WHO, no date)

The emergence and re-emergence of viral haemorrhagic fevers is a growing concern worldwide and there are multiple modes of transmission for viral haemorrhagic fever:

person to person through direct contact with symptomatic patients, body fluids, or cadavers
inadequate infection control in a hospital setting (Crimean–Congo haemorrhagic fever, Lassa, Ebola)
slaughtering practices
consumption of raw meat from infected animals or unpasteurized milk (Crimean–Congo haemorrhagic fever, Rift Valley fever)
direct contact with rodents, or inhalation of or contact with materials contaminated with rodent excreta (Lassa)
mosquito bites (Rift Valley fever, Dengue) or ticks (Crimean–Congo haemorrhagic fever) (WHO EMRO, no date).

Multi-hazard context

Varies with individual diseases

Effective VHF surveillance and control also require international cooperation, bridging gaps between various scientific disciplines and public health initiatives. By pooling knowledge, resources, and strategies on a global scale, the international health community can forge comprehensive and pre-emptive responses to VHF outbreaks. Moreover, local community engagement plays a critical role in the successful implementation of surveillance and control measures. Here, understanding local cultural practices and perceptions of disease is key to designing interventions that are not only effective, but also culturally sensitive and accepted (Hewson, 2024).

Employing advanced technologies like GIS, remote sensing, and genomic sequencing enhances the capability to monitor and analyse the spread and transmission patterns of VHFs in rea-time. Such tools are key to gathering data and generating insights that drive effective public health interventions (Hewson, 2024).

Risk Management

WHO has created a Global Clinical Platform of patient-level anonymized clinical data. It is a secure, limited-access, password-protected platform hosted on REDCap (WHO no date c). The objectives of the Platform are to:

describe the clinical characterization of a disease, its natural history and severity;
identify the association of clinical characteristics of viral haemorrhagic fevers with outcomes; and
enable an understanding of the clinical resource-use when providing high-quality supportive care (WHO no date b).

Previous versions of this platform have captured data for individual viral haemorrhagic fevers, for example, Marburg Virus Disease, Ebola Virus Disease and Sudan Virus Disease. This latest version aims to be a common tool which can be used in these and other illnesses and may allow future comparison between viral diseases. WHO invites Member States, health facilities and other entities to participate in the global effort to collect anonymized clinical data relating to suspected or confirmed cases of viral haemorrhagic fever and contribute data to the WHO Global Clinical Platform (WHO no date c).

The WHO R&D Blueprint for Epidemics functions as a global platform for research and development collaboration, stressing the significance of international cooperation in expediting the research and development of medical countermeasures (MCMs) to respond to epidemics and pandemics. At the core of its efforts lies the concept of 'pathogen prioritization'. Several VHF have been identified as priorities for research to generate results to inform regulatory assessment and policy decisions, while ensuring that national and individual interests are respected. Such simple protocols can be integrated into the outbreak response (WHO, 2024).

Monitoring

WHO supports countries to conduct all-hazards strategic risk assessment in the contexts of health emergencies and disasters, which results in the development of a country risk profile. Empowered with the country risk profile, inclusive of a seasonal risk calendar, countries can anticipate potential emergencies before they occur to trigger early alerts and inform early actions (WHO, 2021).

WHO's Early Warning, Alert and Response System (EWARS) has been designed to improve disease outbreak detection in emergency settings, such as in countries in conflict or following a natural disaster. It is a simple and cost-effective way to rapidly set up a disease surveillance system. EWARS is deployed during an emergency as an adjunct to the national disease surveillance system. WHO works with Ministries of Health and health sector partners to train local health workers to use the system. After the emergency, EWARS should re-integrate back into the national system (WHO, no date b).