L2- pandemics Flashcards
what is epidemiology?
- a branch of medical science that deals with the incidence, distribution, and control of disease in a population
- sum of factors controlling the presence or absence of a disease or pathogen
what are the three factors/epidemiological triangle that influence spread of disease?
the Host (age, sex, race, immune status, etc) Environment (temperature, altitude, crowding, housing,etc) and Agent (biologic, chemical, physical, nutrition)
what are impacts that change factors of the epidemiological triangle?
- zoonotic spillover from increased contact between humans and animal reservoirs
- rising environmental temperatures, increasing vector populations of insect-borne diseases
- increased HIV prevalence shifts immunological landscape in human hosts
define endemic
the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area
define epidemic
an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area
define pandemic
an epidemic that has spread over several countries or continents, usually affecting a large number of people
define outbreak
same definition as epidemic, but is often used for a more limited geographic area
define cluster
refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known
define sporadic
a disease that occurs infrequently and irregularly
what are examples of some endemic diseases?
influenza, malaria, HIV, Measles, tuberculosis, cholera
what are the different pandemic scenarios?
- increase in multiple countries
- increase in some countries and appearance in new countries
what are the 6 phases of a pandemic?
Phase 1: no new reports of zoonotic transmission
Phase 2: animal virus known to have infected humans
Phase 3: sporadic outbreaks in people but no sustained level of community or human-to-human infection
Phase 4: community level and human-to-human outbreaks , significant increase risk of pandemic
Phase 5: human-to-human outbreaks in two countries in one region
Phase 6: human to human outbreaks in at least one country in another region
post peak
post pandemic
what was the main shift in pandemics over history?
gradual shift from bacterial to viral pathogens - due to antigenic shifts
what is HA (hemagglutinin)
a receptor on viruses that allows the virus to bind to host cells. Different HA have specificities for molecules expressed by airway cells - this is why some viruses infect the upper airways and some the lower
what is NA (neuraminidase)?
receptor on the virus that allows the release of viruses from the cell - important for entry into the cells and the spread of progeny viruses
what kind of virus is influenza?
a negative-strand RNA virus
what is RNA highly prone to?
mutations
why is influenza very prone to mutations?
it is an RNA virus and single-stranded which is also a factor that makes it even more prone to mutations. there is also no proof-reading during replication
what is antigenic drift?
mutations of capsid proteins
what happens if two different influenza viruses infect the same cell?
reassortment occurs, generating new viruses
what can reassortment lead to?
antigenic shift
why is antigenic shift so significant?
creates new strains of a virus that could undergo major change in the capsid proteins which would be completely unrecognizable to the immune system, and therefore would inhibit an adequate response
what does antigenic shift allow in viruses that are usually not able to infect humans?
allows viruses to acquire genes from human viruses allowing the pathogen to jump species (inter-species)
what are increasing risks of disease emergence and spread?
- increasing population density
- travel - brings a steady supply of novel pathogens
- reluctance to report
- spread of vectors and vector-borne disease
