Lecture 7: Arbo and Zoonotic Viral diseases Flashcards
Enzootic
Infections firmly established in animal populations, and
transmit from animal to humans with little or
no subsequent human-to-human transmission
(e.g. Rabies)
Epizootic
Infections that spread
efficiently between humans (human-to-human transmission) once introduced from an animal reservoir, leading
to localized outbreaks (e.g. Ebola virus disease)
What are the five different stages of zoonotic virus
adaptation?
- First stage: natural reservoir
- Second stage: Infection of humans with the virus is established, with no human-to-human transmission
- Third Stage: Human-human transmission is limited or very rare
- Fouth stage: Human to human transmission is established
- Fifth stage: represents an
exclusive pathogen of the human species, which results from the previous adaptive stages
What are possible causes of emerging infectious diseases??
- Previously undetected or unknown infectious agents (“new” or “novel”)
- Known agents that have spread to new geographic locations or new
populations - Previously known agents whose role in specific diseases has previously
gone unrecognized.
What is disease re-emergence?
- Incidence of disease had significantly declined in the past, but whose incidence of
disease has reappeared.
What are the two factors that drive emergence of zoonotic infections?
- External factors (factors that produce conditions that allow a pathogen to expand or adapt to a new niche or place.
- Internal factors (genetic adaptations)
What are the drivers of emergence found under external factors?
*These drivers can act locally, nationally, regionally and globally.
- Ecological – global climate change, habitat
encroachment, deforestation - Political – unrest, war, displacement of vulnerable
communities - Economical/socio-economic – poverty, food security,
global population growth, population mobility,
urbanization - Social – behaviors and cultural factors
- Technological – ability to detect diseases
What’s an emerging disease?
- The disease that has appeared in a population for the first time
- or the disease that may have existed previously, but is rapidly increasing in
incidence or geographic range
Which virus groups are the most emerging pathogens? RNAs or DNAs
RNA
Why and how are RNA viruses most capable of emerging ad re-emerging?
- Mutations
- Recombination / reassortment
What are the challenges resulting from emerging and re-emerging viruses??
- Unknown reasons for change in virulence of known viruses
- Novel viruses of high pathogenic potential
- No antiviral treatment / prophylaxis for majority of these viral infections
What are the burdens caused by zoonotic infections?
- Impact on health
*morbidity and mortality associated with the disease
*impact on health systems (access to health care) - Impact on economy
*cost of detection and response
*indirect costs due to losses to business and travel - Social disruption of epidemics (and pandemics)
*stigma of disease
*impact on mental health
*impact on social institutions, such as schools, churches etc.
What are the general features of viral zoonotic diseases?
- Often restricted in geographical spread as it relates to the natural reservoir of the virus
- Considered to be emerging or re-emerging
- Miss- or underdiagnosed
- No specific anti-viral therapies available
- No or very few prophylactic or therapeutic vaccines available
- Associated with wide scope of clinical presentation in
hosts:
Zoonotic infections are classified into 4 categories. What are those?
- Emerging or Re-emerging
- Zoonotic cycle
- Mode of transmission
- clinical manifestations
What’s a virus caused by sandflies?
Toscana virus
