Viral haemorrhagic fevers (VHFs) are dangerous infectious diseases caused by viruses belonging to several groups. All infected people are put at risk of severe illness or death, although some may be less seriously affected. Where there is effective patient care and infection control, human-to-human transmission becomes less likely.
VHFs do not occur naturally in the UK. They are seen occasionally in travellers returning from countries where these diseases are present. Such countries occur across:
- Asia
- Africa
- the Americas
- Europe
All VHFs can cause non-specific symptoms such as:
- nausea
- vomiting
- diarrhoea
- pain
- fever
They can also cause haemorrhagic symptoms in later stages; being the failure of blood to clot, leading to bruising, as well as bleeding from gums and orifices. These symptoms vary both in proportion affected and in severity of symptoms depending on the disease.
VHFs
Ebola virus disease
Ebola virus disease (EVD) is part of the Filovirus family of viruses and found in Central and West Africa. With EVD:
- severe haemorrhagic disease is common
- death occurs in up to 60% of cases
- bats and non-human primates are suspected to be a source of infection
Transmission can occur when there is contact with body fluids of infected people and animals or with fomites (non-living items that can carry infection, for example furniture, bedding, and medical equipment).
Marburg virus disease
Marburg virus disease is also part of the Filovirus family. It's found in East, Central and Southern Africa and causes a disease similar to that caused by Ebola virus. Like EVD, bats are suspected to be a source of infection. Transmission can also happen when there's contact with:
- body fluid of infected humans and animals, such as monkeys
- fomites that have been contaminated with the virus
Crimean-Congo haemorrhagic fever
Crimean-Congo haemorrhagic fever (CCHF) is part of the Bunyavirus family of viruses and is found in:
- Africa
- the Middle East
- Western Asia
- Eastern Europe
- Southern Europe
Transmission is through a tick bite but it can also be transmitted if there's contact with the body fluid of infected people, contaminated fomites as well as sheep or cattle after they've been slaughtered.
Lassa fever
Lassa fever is a member of the Arenavirus family of viruses and is found in West Africa. It's an infection of rodents and is transmitted to humans in conditions of poor hygiene through contact with a rodent's:
Transmission also occurs through contact with infected people as well with contaminated fomites.
Yellow fever
Yellow fever is a member of the Flavivirus family that's found in Sub-Saharan Africa and South America. Monkeys are a source of infection and the usual route of transmission is through an Aedes mosquito bite. In rare cases, transmission can also happen through a blood transfusion or organ graft. A minority of cases develop haemorrhagic symptoms or toxic yellow fever but a highly effective vaccine is available that offers life-long protection.
Dengue fever
Dengue fever is part of the Flavivirus family and it's usually transmitted through an Aedes mosquito bite. In rare cases, as with yellow fever, transmission can also occur through a blood transfusion or organ graft. Haemorrhagic dengue occurs in a minority of cases. This member of the Flavivirus family is found in most tropical and sub-tropical regions of the world, this includes:
- Sub-Saharan Africa
- South America
- the Middle East
- Asia
With sporadic reports from Southern Europe, it's occasionally seen in warmer parts of Europe too.
Haemorrhagic fever with renal syndrome
Haemorrhagic fever with renal syndrome (HFRS) is caused by hantaviruses, members of the Bunyavirus family of viruses, which are found in all inhabited regions of the world. HFRS is mainly seen in Europe and Asia. These viruses infect rodents and can be transmitted to humans in conditions of poor hygiene through contact with a rodent's:
There's also occasional transmission to humans from infected people.
Other
There are many rarely seen VHFs. These are transmitted to humans by ticks or contact with animal body fluids. Examples are:
- Alkhurma haemorrhagic fever, initially isolated from a patient in Saudi Arabia
- Omsk haemorrhagic fever, this is mainly found in Russia
- A number of VHF viruses that affect humans occur in in localised areas South America (Guanarito, Junin, Machupo, Chapare, and Sabia) which are associated with transmission from rodents via urine and faeces
