Meaning and Causes
Viral haemorrhagic fevers are a group of severe illnesses caused by viruses that can damage blood vessels, disturb blood clotting and affect several organ systems.
They are caused mainly by viruses belonging to four families:
- Filoviridae, including Ebola and Marburg viruses
- Arenaviridae, including Lassa fever virus
- Flaviviridae, including dengue and yellow fever viruses
- Nairoviridae, including Crimean-Congo haemorrhagic fever virus
The term describes a group of diseases rather than one specific infection. Not every patient develops visible bleeding, and some infections may remain mild.
Transmission
Transmission varies according to the virus.
Possible sources include:
- mosquitoes and ticks;
- rodents and bats;
- infected livestock or wild animals;
- direct contact with infected blood or bodily fluids;
- contaminated medical equipment;
- unsafe burial practices.
Some viral haemorrhagic fevers, such as dengue and yellow fever, are mainly vector-borne. Others, such as Ebola and Lassa fever, may spread through contact with infected animals or humans.
Transmission risk is often higher among healthcare workers, laboratory personnel, family caregivers and people handling infected animals.
Symptoms and Complications
Early symptoms are often non-specific and may include:
- sudden fever;
- severe weakness;
- headache;
- muscle and joint pain;
- nausea and vomiting;
- abdominal pain;
- diarrhoea.
Severe disease may cause:
- damage to small blood vessels;
- low blood pressure;
- shock;
- internal or external bleeding;
- liver and kidney dysfunction;
- neurological complications;
- multiple-organ failure.
Bleeding may occur from the gums, nose, digestive tract or injection sites. However, shock and organ failure may be more important causes of death than visible haemorrhage.
Diagnosis and Treatment
Diagnosis is difficult because early symptoms may resemble malaria, typhoid, leptospirosis and other febrile illnesses.
Confirmation may involve:
- reverse transcription polymerase chain reaction;
- antigen-detection tests;
- antibody tests;
- specialised virus-isolation techniques.
Samples must be handled under strict biosafety conditions because some of these viruses are highly infectious.
Treatment depends on the specific disease but generally includes:
- fluid and electrolyte replacement;
- maintenance of oxygen and blood pressure;
- management of bleeding;
- treatment of secondary infections;
- organ-supportive care;
- isolation where person-to-person transmission is possible.
Specific antiviral drugs or antibody treatments are available only for some infections. Antibiotics do not act against the viruses themselves.
Prevention and Public-Health Response
Prevention varies with the route of transmission.
Important measures include:
- mosquito and tick control;
- rodent-proof food and housing;
- safe handling of animals and animal products;
- use of personal protective equipment;
- sterilisation of medical equipment;
- isolation of suspected cases;
- contact tracing;
- safe and dignified burial practices;
- vaccination where available.
Vaccines exist for diseases such as yellow fever and certain forms of Ebola. Effective dengue vaccination depends on the approved vaccine, age group and local public-health recommendations.
Outbreak control requires strong surveillance, laboratory capacity, trained health workers and community trust. Conflict, migration, misinformation and weak health systems can allow infections to spread rapidly.
Conclusion
Viral haemorrhagic fevers are a diverse group of infections that may cause vascular damage, shock, bleeding and organ failure. Early recognition, safe clinical care, infection control, vector management and rapid public-health response are essential for reducing mortality and preventing outbreaks.
