Viral Haemorrhagic Fevers (VHF)
Summary
Viral Haemorrhagic Fevers (VHFs) are a group of severe, life-threatening multisystem illnesses caused by distinct RNA virus families. They are characterized by Fever, Vascular Damage (capillary leak), and Coagulopathy (bleeding). Because of their high mortality and potential for person-to-person spread (mostly), they are classified as high-consequence infectious diseases (HCID). [1,2]
Key Virus Families
- Filoviridae: Ebola, Marburg. (Bats/Primates).
- Arenaviridae: Lassa Fever. (Rodents).
- Bunyaviridae: Crimean-Congo Haemorrhagic Fever (CCHF). (Ticks/Livestock).
- Flaviviridae: Yellow Fever, Dengue. (Mosquitoes).
Clinical Pearls
The Malaria Trap: In any patient returning from the tropics with a fever, Malaria is the #1 diagnosis until proven otherwise. Malaria is common and treatable; VHF is rare. However, Plasmodium falciparum can mimic VHF (fever, shock, bleeding). You must test for both safely.
The "21 Day" Rule: The incubation period for most VHFs (Ebola/Lassa) is up to 21 days. A patient who returned >21 days ago and has been well until today is extremely unlikely to have primary VHF.
"Wet" vs "Dry":
- Dry Phase (Day 1-3): Fever, weakness, severe myalgia (flu-like).
- Wet Phase (Day 4+): Diarrhoea, vomiting, bleeding. This phase is highly infectious due to the viral load in fluids.
Geography
- Ebola/Marburg: Sub-Saharan Africa (DRC, Uganda, West Africa).
- Lassa Fever: West Africa (Nigeria, Sierra Leone).
- CCHF: Eastern Europe, Mediterranean, Central Asia, Africa.
- Yellow Fever: South America, Africa.
Transmission
- Primary: Spillover from animal host (Bat, Rat, Tick) to human.
- Secondary: Human-to-human.
- Contact: Direct contact with blood, vomit, faeces, sweat, semen, or breast milk (Ebola/Marburg/Lassa).
- Aerosol: Lassa Fever can be aerosolized from rat urine dust.
- Nosocomial: Healthcare workers are at extreme risk if PPE is breached.
Mechanism
- Cytokine Storm: Massive release of pro-inflammatory cytokines causes vascular permeability (shock).
- Coagulopathy: Virus damages hepatocytes (loss of clotting factors) and consumes platelets (DIC).
- Immune Paralysis: Virus disables Type 1 Interferon response.
Initial Symptoms (Non-specific)
Progressive Symptoms
- Rash: Maculopapular rash (Ebola/Marburg) - typically around day 5-7.
- Eyes: Conjunctival injection (Red eyes).
- Abdomen: Tender, Hepatomegaly.
The "High Risk" Sample
- WARNING: Do NOT send routine bloods to the lab if VHF is suspected. The samples are highly infectious.
- Discuss with local Infectious Diseases / Microbiology consultant immediately.
- Point-of-Care (POCT) Malaria testing is often used at bedside to avoid lab processing.
Specific Tests
- PCR: Gold standard. Detection of viral RNA in blood.
- Serology: IgM (acute), IgG (convalescent).
Findings
- FBC: Leukopenia (low WBC) followed by Leukocytosis. Thrombocytopenia.
- U&E: AKI (Prerenal -> ATN). Electrolyte Derangement (K+, Mg+, Ca+ loss from diarrhoea).
- LFTs: Markedly elevated Transaminases (AST > ALT).
- Coag: Prolonged PT/APTT (DIC).
Management Algorithm
FEVER + TRAVEL (less than 21 DAYS)
↓
ISOLATE IMMEDIATELY
- Side room (Negative pressure if available)
- Full PPE (Cover all skin)
- Notify Public Health / ID Team
↓
RISK ASSESSMENT
- Exact location (Rural/Urban?)
- Exposures (Funerals? Hospitals? Caves? Animals?)
↓
┌───────────┴───────────┐
HIGH RISK LOW RISK
(Known contact / (Tourist / Usually
Endemic area) Malaria)
↓ ↓
SPECIALIST CENTRE LOCAL TESTING
(Transfer to HLIU) (Malaria film -
with precautions)
1. Isolation & Infection Control
- Strict PPE: Double gloves, gowns, face shields, respirators (N95/FFP3).
- Waste: All waste must be incinerated.
- HLIU: High Level Isolation Units (e.g., Royal Free Hospital in UK) for confirmed cases.
2. Supportive Care
- Fluids: Aggressive IV rehydration is the main determinant of survival. Hypovolaemia from diarrhoea is the killer.
- Electrolytes: Correct Hypokalaemia/Hypomagnesaemia.
- Blood: Platelets/plasma for DIC.
3. Specific Therapies
- Ebola: Monoclonal antibodies (e.g., Inmazeb, Ebanga) significantly improve survival.
- Lassa/CCHF: Ribavirin (Antiviral) is effective if started early.
- Multi-Organ Failure: Renal, Hepatic, Respiratory.
- Post-Ebola Syndrome: Uveitis, Arthralgia, Scrotal pain (Virus persists in immune-priviliged sites like eyes/testes for months).
- Sexual Transmission: Survivors can transmit virus in semen for >1 year.
- Ebola (Zaire): Mortality 50-90% (untreated), drops to 30% with optimal care.
- Marburg: Mortality 25-80%.
- Lassa: Mortality 1% overall, but 15-20% in hospitalized severe cases.
- Yellow Fever: 20-50% in severe toxic phase.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| VHF Mgmt | WHO | Fluid resuscitation guidelines. PPE standards. |
| HCID | Public Health England | Categorisation of High Consequence Infectious Diseases. |
Landmark Evidence
1. PALM Trial (NEJM)
- Randomized trial in DRC (Ebola) showing that monoclonal antibodies (MAb114 and REGN-EB3) were superior to ZMapp and Remdesivir, establishing them as standard of care.
What is a Haemorrhagic Fever?
It is a severe viral infection caught from animals or insects in certain parts of the world. It causes a high fever and makes your blood vessels leaky, which can lead to bleeding and shock.
How do you catch it?
Most (like Ebola) are caught by touching the body fluids (blood, vomit, sweat) of someone who is sick, or by caring for them. Lassa fever is caught from dust contaminated by rat urine. Yellow fever is from mosquito bites.
Is there a cure?
For Ebola, we now have powerful antibody treatments. For others, excellent intensive care (fluids, blood support) is the key to survival while the body fights the virus.
Primary Sources
- Mulangu S, et al. A Randomized, Controlled Trial of Ebola Virus Disease Therapeutics. N Engl J Med. 2019. (PALM Trial).
- Uyeki TM, et al. Clinical Management of Ebola Virus Disease in the United States and Europe. N Engl J Med. 2016.
- World Health Organization. Clinical management of patients with viral haemorrhagic fever: a pocket guide for the front-line health worker. 2014.
Common Exam Questions
- Diagnosis: "Fever less than 21 days from West Africa?"
- Answer: Isolate. Test for Malaria AND Lassa/Ebola.
- Vector: "Lassa Fever?"
- Answer: Multimammate Rat (Mastomys).
- Treatment: "Drug for Lassa/CCHF?"
- Answer: Ribavirin.
- Pathology: "Primary cause of death?"
- Answer: Hypovolaemic Shock (fluid loss/leakage).
Viva Points
- Yellow Fever: Why is it unique? It causes massive liver necrosis (Jaundice - hence "Yellow") and has a safe, effective vaccine (17D). If travelled to South America/Africa without vaccine -> High suspicion.
- Viral Persistence: Why check semen? Ebola hides in testes. Males should use condoms for 12 months or until semen tests negative twice.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.