Ebola Flashcards
(29 cards)
Define EVD and what’s it’s former name?
- EVD (formerly Ebola hemorrhagic fever) is a severe, often fatal illness caused by Ebola virus, a Filovirus
Hosts
- Affects humans and nonhuman primates (e.g., monkeys, gorillas, chimpanzees).
How was ebola named?
- Named after the Ebola River in the Democratic Republic of Congo (formerly Zaire), site of the first recognized outbreak in 1976.
When was the first Ebola Outbreak?
First outbreaks (1976)
- Two major outbreaks in Central Africa are? :
- DR Congo (Zaire): near Ebola River.
- South Sudan: \~850 km away.
- Over 500 cases and 400 deaths.
- Healthcare workers infected via contact with blood, excreta, and patients.
Subsequent outbreaks
- Uganda: 2000
- DR Congo: 1995, 2001, 2002, 2003
- Gabon: 1994, 1996, 1997, 2002
- South Africa: 1996
- Sudan: 2004
Where had the Largest outbreak: West Africa (2013–2016)
- Countries: Guinea, Liberia, Sierra Leone
- 28,646 cases, 11,323 deaths
Explain the Nigeria outbreak (2014)
- Index case: Patrick Sawyer, a Liberian-American, flew to Lagos on July 20, 2014
- Became ill on arrival, died 5 days later
- Transmission to healthcare workers:
- Nurse Justina Ejelonu died August 5
- Dr. Ameyo Adadevoh, who treated Sawyer, died August 19
- 20 total cases, 8 deaths
- 4 deaths among healthcare workers
What are the possible hosts for EVD? and it’s likely?
- Likely natural hosts: African fruit bats (family Pteropodidae)
- Other possible animal reservoirs:
- Chimpanzees, gorillas, monkeys
- Forest antelope, porcupines
______ Transmission (Animal to Human) happened In ebola? And how does it spread?
Zoonotic Transmission (Animal to Human
- Ebola enters human population through:
- Contact with blood, secretions, organs, or other bodily fluids of infected animals
- Common during hunting, butchering, or consumption of bushmeat
3. Human-to-Human Transmission
Occurs via direct contact through broken skin or mucous membranes with:
- Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, semen) of an infected or deceased person
- Contaminated objects (e.g., needles, bedding, clothing)
4. High-Risk Settings
- Healthcare workers are at risk during:
- Patient care without proper infection control measures
- Funeral practices:
- Direct contact with dead bodies during burial rituals
What’s the Classification of EVD?
- Family: Filoviridae
- Genera in family:
- Ebolavirus
- Marburgvirus
- Cuevavirus
- All cause viral hemorrhagic fever (VHF)
What’s the 2. Structure of EVD
- Genome: Single-stranded, negative-sense RNA
- Enclosed in:
- Nucleocapsid
- Lipid envelope
- Highly virulent; requires BSL-4 containment in labs
Ebola virus is inactivated by?:
- Heating at 60°C for 30 minutes
- UV and gamma irradiation
- Lipid solvents, bleach, and phenolic disinfectants
4. What are the Major Ebola Virus Species
- Zaire ebolavirus (most virulent)
- Sudan ebolavirus
- Bundibugyo ebolavirus
- Reston ebolavirus (non-pathogenic to humans)
- Taï Forest ebolavirus
Whats the Pathogenesis of Ebola Virus Disease
1. Entry and Spread
- Virus enters through mucous membranes, broken skin, or parenterally.
- Early targets: monocytes, macrophages, and dendritic cells.
- These infected immune cells carry the virus to lymph nodes, liver, spleen, and adrenal glands.
2. Cytokine Storm and Inflammation
- Infected monocytes and macrophages release massive amounts of proinflammatory cytokines (e.g., TNF-α, IL-6).
- This causes a cytokine storm leading to:
- Fever
- Vascular leakage
- Tissue damage
3. Immune Evasion
- Dendritic cells fail to mature → ineffective T cell activation.
- Lymphocyte apoptosis occurs even though lymphocytes are not infected.
- Result: Immunosuppression, viremia, and rapid viral replication.
4. Vascular Dysfunction
- Virus infects endothelial cells, causing:
- Loss of barrier function
- Increased permeability
- Widespread hemorrhage
- Leads to hypovolemic shock and multi-organ failure.
5. Organ Damage
- High viral loads in liver, spleen, lungs, kidneys.
- Liver: Hepatocyte necrosis → reduced coagulation factors → worsens bleeding.
- Adrenal glands: Damage → hypotension and electrolyte imbalance.
6. Coagulopathy
- Disseminated intravascular coagulation (DIC) contributes to:
- Bleeding diathesis
- Thrombocytopenia
- Microvascular thrombosis
Summary:
Ebola virus disables the immune system, damages blood vessels, and triggers uncontrolled inflammation. This combination causes bleeding, shock, and organ failure.
- Targets of EVD are? (In the immune system):
- Macrophages
- Dendritic cells
- Fibroblasts
- Endothelial cells
2. Systemic Spread
- High viral titers found in:?
- Liver
- Spleen
- Lungs
- Kidneys
- Blood and body fluids
3. Immune Effects
- Ebola is immunosuppressive:
- Inhibits dendritic cell function
- Impairs humoral (antibody) response
What are the Clinical Features of Ebola Virus Disease?
What’s the incubation period of EVD
Early symptoms
Progressive
Late
End stage sign
Incubation Period:
2–21 days (typically 4–10 days)
Early Symptoms (non-specific):
- Fever
- Fatigue
- Muscle pain
- Headache
- Sore throat
Progressive Symptoms (gastrointestinal + systemic):
- Vomiting
- Diarrhea
- Rash
Late Symptoms (bleeding phase):
- Internal bleeding: GI tract, lungs, etc.
- External bleeding:
- Eyes, ears, nose
- Mouth and rectum
- Petechiae or hemorrhagic rashes
End-stage Signs:
- Disseminated intravascular coagulation (DIC)
- Hypovolemic shock
- Coma
What’s the mortality rate of EVD and which sub species has the highest?
Mortality:
- 25–90% (Zaire subtype has the highest)
Ebola Case Definitions (for surveillance and response)
1. Alert Case
- Fever with no response to treatment for usual causes (e.g., malaria, typhoid)
- Occurs in an endemic or outbreak area
2. Suspected Case
- Fever + ≥3 of the following:
- Headache
- Anorexia
- Lethargy
- Muscle/joint pain
- Vomiting or diarrhea
- Abdominal pain
- Breathing difficulty
- Difficulty swallowing
- Hiccups
- OR any unexplained bleeding
3. Probable Case
- Suspected case with an epidemiological link
- Contact with a confirmed case
- Attendance at a burial or health facility treating Ebola patients
4. Confirmed Case
- Lab-confirmed infection (e.g., RT-PCR, antigen detection, virus isolation)
Laboratory Diagnosis
Antibody-capture by ELISA
Antigen-capture detection by ELISA
Reverse transcriptase (RT-PCR)
Electron microscopy·
Virus isolation by cell culture in BSL 4
Other lab tests
FBC - Leukopaenia or leucocytosis Thrombocytopenia, Anemia or hemoconcentration
LFT - Elevated liver enzymes (AST, ALT).
E/U/Cr-
Urinalysis- Proteinuria, hematuria, and oliguria
Treatment
Supportive care - rehydration with oral or intravenous fluids - and treatment of specific symptoms improves survival
There is no standard treatment for Ebola HF.
Vaccine – Ervebo, Zabdeno-and-Mvabea under trials
Experimental therapies
Z MAPP
Immunotherapy – use of convalescent serum
Prevention and control
Outbreak control include case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilization
Reducing the risk of wildlife-to-human transmission
Reducing the risk of human-to-human transmission
Prevention and control cont’d
Safe and dignified burial of the dead
Reducing the risk of possible sexual transmission
Reducing the risk of transmission from pregnancy related fluids and tissue
Health-care workers should always take standard precautions when caring for patients
Diagnosis of Ebola Virus Disease
Key Principle:
- Requires high index of suspicion due to nonspecific early symptoms.
Clinical Clues
- Recent travel to endemic areas
- Close contact with confirmed or suspected cases
- Unexplained fever not responding to antimalarials or antibiotics
- History of contact with bodily fluids or burial rituals
Whatre the Immediate Actions to take?
- Isolate suspected and probable cases immediately
- Implement standard and transmission-based precautions
- Notify public health authorities
