Lecture 4 Flashcards
What are some controls for mass action incidence
-Reduce k (# of contacts) –> social distancing
- Reduce transmission (pi) –> masking, sanitation/ hygiene
What is mass action incidence
Density dependent
B = kpi/N
Infection fatality rate
proportion of infectious that lead to death
Case fatality rate:
proportion of detected cases that lead to death
Which is always bigger case or infection fatality
Case fatality rate
How to control R’
gamma –> isolation once youre sick
What is a way to control alpha death model
Getting treatment to prevent death and remove from infectious
What type of virus causes influenza?
Single-stranded RNA
-orthomyoviridae
What determines host immunity for influenza?
Surface proteins, like hemagglutinin and neuraminidase
Why would the attack rate be low in the USA for influenza?
Attack rate must be low because R0 is low due to preexisting immunity (vaccines help this)
-we’ve all gotten the flu at some point
The spanish flu affected mostly?
young adults
Influenza types
A (bird flu), B (human), C (human) , D (humans, cows, pigs)
How do influenza pandemics occur
They occur when a new strain for which we have no immunity evolves or one spills over into humans
What is a cytokine storm
Cytokine storm is an immune system phenomenon when your immune system sees something unfamiliar and freaks out, leading to an immune response that is dangerous to your own health
Why might there be multiple waves of infection?
R0 changes due to behavioral changes (social changes)
-evolution of virus
-R0 can die out and pick up again
What is TB caused by?
Bacterium, Mycobacterium tuberculosis
What does it mean when we say TB is in the latent phase?
Some level of TB exists in the person, but not enough to show symptoms or be infectious
How did we achieve lower TB levels in human populations?
Non-pharmaceutical approaches (decreasing transmission via decreasing contact in dense areas by isolating infected patients), then antibiotics and vaccines
What is an SEI model
Latent phase with no recovery
-Susceptible, Exposed, infectious
- Ex: tuberculosis
What is HIV? What does it cause?
RNA virus called Human Immunodeficiency Virus which causes AIDs (Acquired Immuno-Deficiency Syndrome)
Why don’t the symptoms of HIV appear in a person even though they are infected?
The immune system is able to keep HIV to a low load, but it eventually increases beyond the immune system’s capability leading to symptoms of AIDs
What makes HIV and Covid-19 similar?
Like Covid-19, HIV is asymptomatic, so it is able to be spread by individuals who do not know they are infected
What kind of model might be appropriate for HIV?
SEI
-Exposed/latent period with no recovery
What is theta?
Proportion of infections that occur prior to symptoms or by asymptomatic infection
HIV has a low R0, but why is it hard to control
It has a high theta value
