Epidemiology Flashcards
What is epidemiology?
The study of the cause, distribution, control, and prevention of disease in a population
What does distribution mean in terms of epidemiology?
host range (limited or broad)
What do epidemiologists study?
- mechanisms of viral transmission
- risk factors for infection (triad model)
- size of the population needed for virus transmission
viruses love a crowd - geography
- seasonal factors
- means of control
What is the triad model of epidemiology?
Three factors that influence disease caused by viruses
- host, pathogen, environment
Talk about HIV and Influenza.
Both RNA viruses
- HIV RNA Retrovirus
- Influenza: segmented (-) RNA virus (each different segment codes for different protein)
What is hemaglutinin and neuraminidase?
- hemagluttinin: enables entry by binding sialic acid on cell surface and plays role in release from endosome (M2 ion channel for H+ protons)
- neuraminidase: enzyme that enables release from cell cleaves sialic acid molecules on surface so hemaglutinin doesn’t rebind
What is prevalence?
number of EXISTING cases total population or group
What is incidence?
Number of NEW cases (usually new cases per year)
What is the host range of influena?
horses, seals, birds, pigs, humans
What are the features of influenza?
Influenza has a short INCUBATION PERIOD within the host
Time from infection to symptoms is approximately 1 to 2 days
Infected individuals act as ACUTE CARRIERS and spreaders of the virus
Infected individuals readily TRANSMIT the virus by coming
into contact with un-infected individuals or by expelling the
virus into the environment in the form of FOMITES (for example by sneeezing and coughing)
How is influenza transmitted?
animal host to animal host and via fomites
What are the factors that influence the spread of influenzaviruses?
Population density (more dense the better)
Close contact with infected wild and/or domestic animals (transmission from other species to human)
Herd immunity (vaccinated or unvaccinated population)
Migratory patterns of infected birds (avian flu)
Public Health Programs/Disease surveillance
(rapid identification of new strains)
What are the strategies to reduce influenza transmission?
Vaccination
Good disease surveillance
Identification of disease outbreak
Potential quarantine
Antiviral drug development
What opportunistic infections are immunocompromised people opened up to?
Kaposi’s sarcoma (KS)
Candidiasis (thrush)
Pneumocystis carinii pneumonia (PCP)
When researchers were searching for the cause of the disease referred to as the “gay cancer” or gay-related immunodeficiency disease (G.R.I.D.), what did they know?
1) Each patient was immunocompromised
2) High mortality rate approaching 100%
3) Primarily gay men afflicted with disease
4) No treatment
When researchers were searching for the cause of the disease referred to as the “gay cancer” or gay-related immunodeficiency disease (G.R.I.D.), what were their Theories about etiology of disease?
- Amyl nitrates (poppers) used as sexual stimulants
- STD (viral, bacterial, fungal?)
- Environmental agent/factor
- Multiple others
What data collected by clinicians and scientists leads to the conclusion that GRID is caused by a pathogen?
1) Heterosexuals dying from disease (first reports in Haitian immigrants)
2) The epidemiology of the disease (pattern of spread) suggests that the etiologic agent of disease is transmissible (virus or bacteria)
3) People infected via blood transfusions, many hemophiliacs contract the disease
What are the four H’s of ppl infected w/ HIV?
Homosexuals
Haitains
Hemophiliacs
Heroin Users
What are the reservoirs of HIV and how is it spread?
Humans are the main RESERVOIRS of HIV
HIV is spread by CHRONIC carriers of HIV
- chronic/persistent infection
These carriers are asymptomatic due to the LONG
INCUBATION PERIOD of HIV thus they can readily
transmit the virus to others
What is the pathogenesis of HIV?
Disease Phases:
- Acute (1 to 2 months)
- flu or mono-like symptoms
Asymptomatic (8 to 10 years)
- “clinical latency”
- immune system in constant battle with HIV
AIDS (Acquired Immune Deficiency Syndrome)
- immunodeficiency (<200 CD4+)
- diseases of nervous, respiratory, and gastrointestinal systems
- opportunistic infections (KS, PCP, thrush)
- death
What are the viral targets of HIV? How is viral load measured?
CD4+ T-cells
- adaptive immune Response
- provide help to B cells and CD8+ T Cells
- prime target for HIV
HIV binds CD4+ receptor to get into T Cell
- initial drop in CD4+ T cells and recovery
- slow/steady decline of CD4+ T Cells as HIV kills them off
HIV RNA = viral load in patient
-initial increase in viral load then clinical latency
Go over human host to human host HIV transmission.
1) Humans are the sole reservoir
2) Spread by direct contact with
HIV-infected cells, blood, semen
3) Modes of transmission
- intimate contact (STD)
- i.v. drug use
- mother to child
in utero
breast-feeding
What are the Factors Positively influencing HIV transmission?
Presence of other STDs
Risky behaviors
- iv drug use (needle sharing) - number of partners
Education (negative influencer)
Geopolitical
- poverty, wars, migration
What are the Strategies to reduce HIV PREVALENCE?
Development and use of effective
anti-retroviral therapies
2) Increased access to and affordability of
life-saving drugs
3) HIV/AIDS education
4) Vaccine?
may have to develop multiple HIV
vaccines against various HIV strains
