Lec 14 Ebola Virus Flashcards
Ebola Virus General
Order: mononegavirales
Family: Filoviridae
Prototype Viral Hemorrhagic Fever Pathogen
Filovirus: enveloped, non-segmented, negative-stranded RNA virus
Severe disease with high case fatality
Absence of specific treatment or vaccine
Zoonotic virus – bats the best reservoir, but species unknown
Spillover event from infected wild animals (e.g., fruit bats, monkey, duiker) to humans, followed by human-human transmission
Ebola Transmission
When an infection does occur in humans, the virus can be spread in several ways to others. Ebola is spread through direct contact (through broken skin or mucous membranes) with blood or body fluids (including but not limited to urine, saliva, feces, vomit, and semen) of a person who is sick with Ebola
objects (like needles and syringes) that have been contaminated with the virus
infected animals
Ebola is not spread through the air or by water, or in general, food. However, in Africa, Ebola may be spread as a result of handling bushmeat (wild animals hunted for food) and contact with infected bats.
Specifics of Ebola Transmission
Virus present in high quantity in blood, body fluids, and excreta of symptomatic Ebola patients
Opportunities for human-to-human transmission
- Direct contact (through broken skin or unprotected mucous membranes) with an Ebola patient’s blood or body fluids
- Sharps injury (with contaminated needle or other sharp)
- Direct contact with the corpse of a person who died of Ebola
- Indirect contact with an Ebola patient’s blood or body fluids via a contaminated object (soiled linens or used utensils)
- Possibly, contact with semen from a recovered male Ebola patient
Ebola can also be transmitted via contact with blood, fluids, or meat of an infected animal
Limited evidence that dogs become infected with Ebola virus
No reports of dogs or cats becoming sick with or transmitting Ebola!
Ebola Human-to-Human Transmission
Human-to-Human Transmission
Extremely low loads of virus can lead to infection, very easy to infect someone. Goes thru mucosal surfaces of skin! Still, not every contact w/ infected individual will transmit the virus.
Infected persons are not contagious until onset of symptoms
Possible that the virus can be transmitted through
semen of a man who has survived Ebola
Infectiousness of body fluids (e.g., viral load) increases as patient becomes more ill
Remains from deceased infected persons are highly infectious
Human-to-human transmission of Ebola virus via inhalation (aerosols) has not been demonstrated
Ebola Virus Pathogenesis
Direct infection of tissues
Immune dysregulation
Hypovolemia and vascular collapse
Electrolyte abnormalities
Multi-organ failure, septic shock
Disseminated intravascular coagulation (DIC) and coagulopathy
Early Clinical Presentation
Early Clinical Presentation
Acute onset; typically 8-10 days after exposure (range 2-21 days)
Signs and symptoms
Initial: Fever, chills, myalgias, malaise, anorexia
After 5 days: GI symptoms, such as nausea, vomiting, watery diarrhea, abdominal pain
Other: Headache, conjunctivitis, hiccups, rash, chest pain, shortness of breath, confusion, seizures
Hemorrhagic symptoms in 18% of cases
Other possible infectious causes of symptoms
Malaria, typhoid fever, meningococcemia, Lassa fever and other bacterial infections (e.g., pneumonia) – all very common in Africa
Host cell targets and infection
1) Monocytes of macrophages, infected, will disseminate all over the body, especially in epithelial and endothelial tissues.
Direct viral damage cell to initially infected cells
Macrophages are deregulated and activate endothelial cells to cause blood vessel inflammation, blood vessels will shrink and form gaps, cause fluid leakage (haemorrhage)
The macrophages are overreacting, secreting cytokines they should not, and stop eating pathogens! The pathogen does not end up in the proper compartment after being swallowed by them.
2) Phagocytize particles bound by antibodies, so macrophages attack the immune system!
Seriousness of Inflammatory Response
a
