Lecture 1: Infectious disease pt 1 Flashcards
1) What causes communicable disease?
2) When was it the leading cause of death and disability?
1) Bacteria, viruses, parasites.
2) Until antibiotics and vaccines
What is R0/ R naught?
Average number of infections produced by an infected individual
Differentiate between incubation period and latent period
1) Incubation = time interval from infection to symptom onset
2) Latent = time interval from infection to becoming infectious
What are the R0s for the following communicable diseases?: measles, mumps, HIV, SARS, ebola, & hep C
1) Measles: 18
2) Mumps: 10
3) HIV: 4
4) SARS: 4
5) Ebola: 2
6) Hep C: 2
List 2 things that can impact R0
1) Route of transmission
2) Period of communicability
1) Who designed criteria to establish a relationship between a microbe and a disease?
2) What two diseases did this person study?
1) Robert Hermann Koch
2) Cholera and TB
List the 4 criteria of Koch’s postulates
1) The organism must be present in every case of the disease
2) The organism must be isolated and grown in the laboratory
3) When injected with the laboratory-grown culture, susceptible test animals must develop the disease
4) The organism must be isolated from the newly infected animals and the process repeated
What are the 3 modifies Koch’s postulates criteria?
1) Association
2) Isolation
3) Transmission
1) Define endemic
2) Define epidemic
3) Define pandemic
1) Transmissions occur, but number of cases remains constant
2) Number of cases increases
3) When epidemics occur on several continents (a global epidemic)
Describe the two steps of case finding for diseases
1) Confidential interviewing
-can be challenging due to social stigmas
2) Epidemiological Treatment: treatment of contacts
1) Where should certain positive disease cases be reported?
2) Whose responsibility is it to report?
3) Who has a list of reportable diseases?
1) Local health department
2) Provider responsibility to report (not the patient)
3) CDC
slide 18
slide 19
What did Koch say abt the burden of TB?
If the importance of a disease for mankind is measured by the number of fatalities it causes, then tuberculosis must be considered much more important than those most feared infectious diseases, plague, cholera and the like. One in seven of all human beings die from tuberculosis. If one only considers the productive middle-age groups, tuberculosis carries away one-third, and often more.
1) From the 1700s-1900s how many deaths occurred due to TB?
2) Koch demonstrated __________ are a contributory cause of disease, but other factors are needed
3) What are these other factors? (3)
1) 1 billion
2) bacilli
3) Reduced immunity, poor nutrition, genetic factors
List 3 major victories in public health that contributed towards fighting TB
1) Isolation in sanitariums
2) Vaccine development
3) Screening with PPD skin tests and chest xrays
1) What important discovery regarding TB occurred in the 1940s?
2) What two things advanced the fight against TB in the 50s?
3) What occurred regarding TB in the 60s?
1) Streptomycin
2) Isoniazid (INH) and Para-aminosalicyclic acid
3) Success prompted closures of sanitoriums and cut backs on screening; “Eradication”
1) When did active TB resurface and why?
2) What era did DOT (directly observed therapy) and adherence to effective treatment occur?
3) How does TB spread? [method of transmission]
1) 1980s; AIDS epidemic & drug resistance increased
2) 1990s
3) Aerosolized droplets
What is the national goal for TB treatment completion rates?
95%
1) What is the number one cause of death from infectious disease in the world?
2) What is the the number one killer of people with HIV?
1) TB
2) TB
Describe the 3 steps to contracting TB
1) Person w active pulmonary TB coughs on you.
2) You breathe droplets containing mycobacterium tuberculosis into lungs.
3) TB bacilli travel to alveoli & proliferate.
1) For infection to occur, about ______ TB bacilli need to reach the lungs
2) Is this high or low relative to other diseases?
3) Once in the lungs, the bacilli are _______________ by __________________ in the lung
1) 10
2) Very low
3) phagocytosed; macrophages
List the infectious doses for:
1) E. coli
2) Vibrio cholera
3) Campylobacter
4) TB
5) Entamoeba coli
1) 10^6 – 10^8
2) 10^4 – 10^6
3) 500
4) 10-50
5) 10
6) 1
What happens after TB bacilli are phagocytosed by macrophages in the lungs?
Instead of being killed, the TB bacilli proliferate in the macrophages for 2-12 weeks until there are thousands of them
1) What happens after TB bacilli proliferate in macrophages until there are thousands?
2) Does this involve antibodies and B cells?
1) Enough antigen has been produced to cause a cellular immune response
2) No; this is different from the humoral response involving antibodies and B cells
What cells are involved in a cellular immune reposne?
CD4 and CD8 T cells attempt to contain the infection and/or kill infected cells
After a cellular immune response is initiated, one of two things can happen; what are they?
1) Latent TB: Infection is contained in Granulomas
OR
2) Active TB: Spreads
Define the 3 types of TB infections
1) Primary: asymptomatic or symptomatic
2) Latent: inactive, non-communicable
3) Reactivation: prior containment
____% of the time, primary TB infection results in latent infection
90%
1) The primary mechanism the immune system has for controlling TB is what?
2) Why?
3) When is a person infected with TB considered to be healthy for all intents and purposes?
1) Walling it off in granulomas
2) Primarily bc of a healthy CD4 and CD8 T-cell response
3) As long the immune system keeps the TB inside granulomas
1) Define granuloma
2) What is a caseating granuloma?
3) Define caseum
1) A rim of healthy macrophages and T cells that act as a wall
2) A granuloma w areas of caseation (areas of necrosis w complete loss of tissue architecture)
3) Soft, dead cell mush
The granuloma is a rim of healthy
macrophages and T cells that are walling off what 4 things?
1) Infected macrophages
2) Dead and dying infected cells
3) Free bacteria
4) Matrix
Why do we care about latent infection? (2 reasons)
1) 5% reactivate in the first 1.5 years after infection
2) 5% reactivate over the remaining lifetime
List the 3 most critical TB symptoms
1) Coughing up blood
2) Unintended weight loss
3) Night sweats
If a pt feels fine, under what circumstances should they be tested for TB?
1) Are they from somewhere where TB is endemic?
2) Is risk of reactivation high?
- Do they have have HIV?
- Otherwise (or about to be) immunosuppressed?
(e.g. on chemotherapy, on TNF inhibitors,
getting HD)
Describe how a Tuberculin skin test (TST) is done
By injecting 0.1 ml of tuberculin purified protein derivative (PPD) intradermally into the inner surface of the forearm.
After the administration of a TB test, 48-72 hours later, the diameter of what is measured?
Induration (NOT erythema)
How do you read a TB test?
By diameter of induration:
1) 5 mm is positive for: HIV+, organ transplant, other immunosuppressed people
2) 10 mm is positive for: recent immigrants from areas with high TB incidence, health care workers, the homeless, and people with hematologic or head/neck malignancies, renal failure, or diabetes
3) 15 mm is positive for: people with no known risk factors
What are the two types of Interferon gamma release assay (IGRA)? What is measured in both?
Quantiferon and T spot; interferon gamma.
