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Ebola 101: the virology behind the
outbreak
Amy L. Hartman, Ph.D.
Assistant Professor
Dept. Infectious Diseases and Microbiology
Pitt Graduate School of Public Health
and
Center for Vaccine Research
Historic
Ebola
outbreaks
1976 – 2014
50 – 90 %
mortality rate
Updated 2014, CDC.gov
Day of infection
Start of incubation period
6-12 days
Day 0 – 3: Early febrile phase: fever, fatigue,
malaise, body aches
Days 3 – 10: Gastrointestinal phase:
abdominal pain, nausea, vomiting, watery diarrhea,
persistent fever, body aches, hiccups
Fatal cases:
Severe dehydration, rapid
breathing, loss of
consciousness
Death 7 – 12 days after onset
of illness
Recovery:
Resolution of GI
symptoms,
rehydration
Human
Clinical
Disease
Important interventions:
Fluid & electrolyte
replacement
Anti-nausea, antidiarrheal therapy
Later complications:
Secondary infections,
encephalitis,
neurological
abnormalities
Schieffelin et al. 2014 NEJM; Chertow et al. 2014 NEJM
Diagnostic testing for Ebola
PCR-based diagnostic testing not reliable until 72
hours after onset of symptoms
Field’s Virology FIGURE 32.12.
Virus in the blood in fatal vs. surviving
cases
Outbreak in Uganda 2000 - 2001
Towner et al. 2004. J Virology
Human-to-human transmission of
Ebola
• Virus shed in bodily fluids
– Blood, saliva (oral/nasal secretions), urine/feces, vomit,
sweat, breast milk
• Direct contact with bodily fluids is required for
transmission
• Mucosal surfaces are main entry point of the virus
– Eyes, mouth, nose
Activities historically associated with
Ebola transmission
• Healthcare
workers
• Traditional
healers
• Spillover from
bat reservoir
• Traditional
burial practices
Direct
contact
with sick
patients
Direct
handling
of dead
bodies
Interaction
with bats
and/or bat
caves
Bushmeat
trade
• Consumption
of wild animal
meat
Why is Ebola so pathogenic?
Virus
replicates to
high levels in
many cell
types
Causes
direct
tissue/cell
death
Causes
vascular
leakage
50 – 90 %
fatality rate
Causes
coagulation
abnormalities
Inhibits the
immune
response
Induces of
harmful
inflammatory
responses
Post-exposure treatments
From Dye et al., PNAS 2012
Prophylactic (preventative) vaccines
Ann Intern Med. Published online August 21, 2014. doi:10.7326/M14-1904
Rapid testing of Ebola vaccines
• NIAID/GSK
– Chimpanzee adenovirus type 3 (ChAd3) vector
– Monovalent and bivalent versions
– Express Ebola glycoprotein (Zaire & Sudan)
• Public Health Agency Canada
– Vesicular Stomatitis Virus (VSV) vector
– Express Ebola glycoprotein
Current West African outbreak
Nov 30th: 17,145 cases with 6,070 deaths
Cumulative cases in West Africa
What makes this outbreak
different from previous
Similarities
•
•
•
•
•
•
Transmission
Symptoms
Incubation period
Serial time
R0
Fatality rate
Differences
•
•
•
•
Scale (30x)
Urban setting
Other socioeconomic issues
Increased human mobility
Factors influencing Ebola outbreaks
Ecological
Virological
• Climate change
• Effect on bat
reservoir &
spillover
dynamics
• Characteristics
of the virus
strain
Sociological
•
•
Human behavior
Urban environment
Questions?