Section 1
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Infectious diseases cause __ % of deaths worldwide
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Section 1
(50 cards)
Infectious diseases cause __ % of deaths worldwide
20%
Reservoir
can be human, animal, or non living
John Snow
Physician and skeptic of miasma theory of cholera. Mapped cases of Cholera in London showing clusters around broad st. Persuaded Soho council to remove pump handle. Cases dropped. Water delivered from polluted section of Thames.
Confirmed case
an infected person. Definitely infected or diseased. Cases that are lab confirmed. Requires lab testing.
Who wrote Airs, Water, and Places about disease causes?
Hippocrates
Host
Organism infected by an agent. Whether and how badly they are infected depends on multiple factors. Example: age, sex, race, previous diseease, etc.
Miasma
A noxious form of bad air that causes epidemics. Poisonous vapor filled with rotting organic matter. Commonly used to explain diseases with crowding. Among main arguments for early public health.
Host/natural reservoir for dengue
Humans
Agent
The infecting organism. Depends on biologic properties, prevention, characteristics of agent.
animal reservoirs (zoonoses)
Diseases that occur primarily in wild or domestic animals that can be transmitted to humans
When were statistics developed to set stage for epi investigations?
Early and mid 1800s
Escape mechanism
properties of an agent that allow it to evade or escape the immune system
Nutritional prevention for agents
Lack of food Access
Ignatz Semelweiss
Hungarian physician Observed wards at a hospital had 3x mortality of midwife wards. Puerperal fever
What did ancient Greece think caused disease?
Hippocrates attributed illness to characteristics of environment: climate soil water. Or human behavior: nutrition lifestyle. If illness has natural cause, should have natural cure in herbs and foods etc.
Probable case
Clinical features consistent with symptoms associated with pathogen
What lead to the discovery of germ theory?
Microscope invention Pasteur germ theory experiments Koch causative agents for infectious disease
Who conducted experiments supporting germ theory
Louis Pasteur 1800s
Characteristics of agents that affect infectivity
escape mechanism
Point source outbreak
Limited to one place and time Everyone exposed at same point in time. Represents distribution of incubation period
Natural reservoir
the long-term host of a pathogen of an infectious disease. Can be a source of disease outbreaks.
Vector for west nile virus
Mosquito
What is infectious disease epidemiology?
Causes are infectious agents which live on or in a larger organism. For infecting organisms to survive, they must eventually leave their host and cause infectious elsewhere. For transmissible or communicable diseases.
Koch's Postulates
1) the microorganism must be present in every case of the disease but absent from healthy individuals 2) the suspected microorganism must be isolated and grown in a pure culture from each case 3) Reinoculation in another host causes disease 4) the same microorganism must be isolated again from the new host
Germ Theory
the theory that infectious diseases are caused by certain microbes
When was the golden era of bacteriology?
Beginning in 1850s
Chemical prevention of agents
Poison Alcohol Smoke
Possible case
suggestive clinical signs but not fit case definition. plot on curve but may not be infected. Have some epi criteria for case definition
Epidemiologic triangle
agent, host, environment framework to understand risk factors for disease. Maps out how disease spreads in human populations
Host/ Natural reservoir for west nile virus
Bird
What did epidemiologic studies do in 17th and 18th centuries?
Mortality trends Fatality rates
Pandemic
Epidemic that is spread through human populations across a large region or worldwide
What are the public health implications of infectious disease epidemiology?
Future incidence is a function of current prevalence/ dependency. Cases are risk factors for future cases- which is not true for chronic cases. Prevent transmission, acquisition, progression of disease.
Non living reservoirs
water, food, soil
Physical prevention for agents
Trauma Radiation Fire
What did Robert Koch do?
1800s 1900s Identified cause of TB, cholera, anthrax. First link to specific micro organism to a specific disease- anthrax. Created 4 criteria to establish relationships between microbe and disease.
Biologic properties of an agent
Is it a bacteria or a virus?
Vector
Any organism that transmits disease from host to host. Must be living. Usually a mosquito or a tick.
How are reservoirs different from vectors?
Vectors are agents of disease transmission. Reservoirs are continuing sources of outbreaks. Many diseases have multiple hosts and vectors
Epidemic
Occurrence of disease in a given human population during a specific period of time in which new cases substantially exceed what is expected
Where was miasma theory developed?
Europe, india, china
Environment
Medium in which hosts and agents interact. Influence how we are infected and transmit disease. Example: seasonality in flu
What can epidemiology do?
Studies shape policy decisions and evidence based practice by identifying risk factors for disease and targets for preventive healthcare
Infection
Being invaded by a pathogen May or may not lead to disease
Targets for prevention in infectious disease epidemiology
1. Prevent acquisition and progression of disease. 2. Prevent transmission.
Who invented the microscope?
1683 Anton van Leeuwenhoek
Disease vs infection
Disease is Infected and symptomatic
When did cholera epidemic in Soho occur?
1854
What is epidemiology?
The study of distribution and determinants of disease and other health related states or events: WHO
Puerperal fever
common in mid 19th centure hospitals Mortality 10%-35%
Section 2
(50 cards)
Types of incidence
Cumulative incidence Incidence rate
Alternate epidemiologic triangle
Have a natural reservoir as well as another. Share the agent.
Why do we measure burden of disease?
to describe risk and determinants of disease
Risk ratio formula
[a/(a+b)]/[c/(c+d)] Cumulative incidence of disease in exposed/ CI of diseased in unexposed
Incidence
Estimates the risk of acquiring a disease. The number of new cases or events that occur or develop in a defined population at risk during a specified time interval (cumulative) or as a function of follow up time (rate)
Is prevalence a proportion or a rate?
A proportion. It is expressed as a percent or number. .183% or 1.83 per 1,000
How to interpret odds ratio
over 1: may be associated with developing disease 1: no association under 1: exposure may be protective 1.3= the odds of getting x illness was 1.3 times higher among people with exposure
Types of prevalence
point prevalence period prevalence
When do we need to calculate an incidence rate?
when population is dynamic. number of people who acquire disease relative to total population is large. need to account for drop outs or loss to follow up
Period prevalence
Count individuals who have and or develop disease over a period of time
Experimental studies
studies in which the independent variables are directly manipulated and the effects on the dependent variable are examined. RCT
How to interpret risk ratio
over 1: may be associated with developing disease 1: no association under 1: exposure may be protective 1.3= those who ate nanaimo had a 1.3 times increased risk of developing food poisoning compared to those who didnt
Analytic sample
Subset of the study population in any given analysis
Interpretation of incidence rate ratio
over 1: may be associated with developing disease 1: no association under 1: exposure may be protective
Rate
a/t Ratio where time is included in the denominator #new cases per 1000 person days of follow up
Pathogens with human reservoir
anything with H suggests a human in the natural reservoir. HIV, HPV
Ratio
a/b or a:b Fraction represented by one quantity to another Measles sex ratio (M:F)
Risk Ratio
The risk of developing a disease relative to exposure to a certain risk factor. A ratio of the probability of disease developing in exposed versus unexposed group. Can be calculated in studies that estimate incidence- cohorts and RCT.
Prevalence formula
number of existing cases at a specific time or interval /number of people in population at a time or interval
systematic review and meta-analysis
Collects all previous studies on the topic and statistically combines their results
Point prevalence
Count individuals who have disease at one point in time
Why do we measure disease?
To determine who is at highest risk. Understand etiology of disease. Measure intensity or degree of infection. Prioritize resources.
case series
involves a small group of patients with a similar diagnosis
Prevalence
The proportion of individuals in a defined population who have the disease at a specific time or interval. Measures the burden of a disease in a population.
Goal of infectious disease epidemiology
to control transmission of disease
Target population
the group of individuals whom we want to infer about . the population that findings are generalized to
Case-control study
A type of epidemiologic study where a group of individuals with the diseases, referred to as cases, are compared to individuals without the disease, referred to as controls
Vector for dengue
mosquito. There is no human to human transmission.
Spillover effect
An event where virus jumps into another triad. Ex. bats infect other primates
Attack rate formula
Number of persons infected/total number of exposed susceptible people during the outbreak
Count measures
a. Number of occurrences # cases of measles
Proportion
a/a+b Ratio where numerator is included in the denominator #of measles cases/total residents
Example alternate epi triangle: ebola
Natural host is fruit bat, environment is jungle, agent is ebola. Alternate host is human, environment is city.
Study population
individuals in the source population who contribute data to the study
What is another name for risk ratio?
Relative risk
Attack rate
Cumulative incidence of infection in a group of exposed and susceptible hosts Measured from the beginning to the end of an outbreak "of those who were exposed, __% were infected over the course of the outbreak"
Odds ratio formula
ad/bc
Types of observational studies
Case report, case series, ecological study, cohort study, case control study
ecologic study
a study in which the units of analysis are populations or groups of people rather than individuals
prevalence ratio (PR)
(a/a+b)/ (c/c+d)
Why do we use measures of association
to compare the risk of disease associated with certain exposures to the risk of disease in absence of exposure. identify risk factors (association) causal relationships Consider them in terms of probability (p values, CI)
Source population
Subset of the target population that can be enumerated and studied
Cumulative incidence formula
Number of new cases of disease during a specified time/ number of people in population at risk at beginning of same time interval expressed as ___ per ___ 0.04 is 4 per 100 4% over period of time. Example 4% over a 5 year period.
Odds ratio
a probability statement about the association between a particular disease and a specific risk factor
Incidence rate formula
number of new cases of disease during specified time/ number of people in population at risk during the same time interval x time units Denominator is also called person time at risk "0.133 per person month at risk" "13.3 per 100 person months"
Incidence rate ratio
incidence rate in exposed/incidence rate in unexposed
Measures of disease frequency
incidence, prevalence
cohort study
A type of epidemiologic study where a group of exposed individuals (individuals who have been exposed to the potential risk factor) and a group of non-exposed individuals are followed over time to determine the incidence of disease
Does association imply causation?
No can be useful to suggest causality, but need evidence to prove it
Case reports
accounts of a single occurrence of a noteworthy health-related incident or small collection of such events
Section 3
(50 cards)
Organisms with soil reservoir
Histoplasma capsulatum Clostridium tetani Clostridium botulinum
Airborne transmission
Inhalation of contaminated air. Infection spread by particles that remain infectious when suspended in air etc. measles
How are viral infections classified
DNA virus RNA virus
Disease
Abnormal state associated with clinical signs, symptoms, and atypical laboratory findings
Progression axis of infectious disease
Exposure Infection Disease- clinical sx Cure or death or chronic infection
Epidemiologist classification of disease
Population Risk Factor Transmission Route Reservoir
What measure of association do you use for a cohort study?
Incidence Relative risk
Top infectious disease causes of death
Lower resp infection Diarrhea disease Tuberculosis
When is knowledge of latency and incubation period critical?
For contact tracing and quarantining of exposed people
Vectorborne transmission
Dependent on biology of vector and infectivity of organism
Latent
State in which the agent is non replicating and generally non infectious
Incubation period
Time from exposure resulting in infection until onset of disease
Indirect contact
through infected fomite, blood, or body fluid
Infection
Agent invades host tissue
How are prion infections classified
Protiens
Latency period
Pre infectiousness period Time from exposure to infectiousness
Is period prevalence a rate?
No, time is defined outside of proportion.
Colonization
Agent persists on a host without infection
How is sepsis classified
Disseminated
How is prevalence ratio interpreted?
pr=3 the prevalence of infection among those who were exposed is 3 times that of the prevalence among non exposed
Prevalence Ratio
[a/(a+b)]/[c/(c+d)] Prevalence of exposed/ Prevalence of unexposed Used in cross sectional studies Ratio of burden in a cross sectional study
Contact transmission
requires direct or indirect contact Ex. MRSA
How are diarrheal diseases classified
Secretory Invasive
What measure of association do you use in a case control study
Odds Ratio
Is attack rate a rate?
NO
Food or waterborne transmission
Ingestion of contaminated food
Physician Classification of Disease
Clinical symptoms Diagnosis Prognosis Pathophysiology Treatment Care
In a cross sectional study, what is more reliable, OR or Prev Ratio?
Prevalence Ratio
Transmission axis of infectious disease
Exposure Pre infectious infection Post infectious
When does an odds ratio approximate the prevalence ratio?
A cross sectional study. It is okay when the overall prevalence of disease is low.
Organism with human reservoir
Treponema pallidum Gonorrhea HIV Hep B Hep C Shigella S typhi
Organism with animal reservoir
Rabies Yersinia pestis Leptospira Nontyphoid salmonella Brucella
How are cardiovascular infections classified
Endocarditis Myocarditis Vasculitis
spillover effect
WHen an animal or human becomes infected with a virus through contact with the reservoir host.
How are respiratory diseases classified
Upper resp lower resp
How are CNS infections classified
Meningitis (bacterial v aseptic) Encephalitis Abscess
Microbiologist classification of disease
Isolation Identification Growth Virulence Pathogenicity
Perinatal transmission
Similar to contact infection; however, the contact may occur in utero during pregnancy or at the time of delivery
zoonoses
Diseases transmitted from animals to humans
Direct contact
skin or sexual contact with an infected individual
When are OR, RR,and PR similar?
When prevalence is low.
What measure of association do you use for RCT
Incidence Relative Risk
What measure of association do you use in a cross sectional study?
Prevalence Prevalence ratio
What does prevalence measure?
The burden of disease
Is time in denominator of period prevalence?
No, it sits outside
How are bacterial infections classifed
gram negative gram positive
How are parasitic infections classified
Protozoa Helminths Trematodes Cestodes
When is quarantine most effective?
When latency period is shorter than the incubation period
How are fungal infections classified
Disseminated Localized
Organism with water as reservoir
Legionella Pseudomonas aeruginosa Mycobacterium marinum
Section 4
(50 cards)
Reproductive number of HIV AIDS
2-5`
Infectious period
period from onset of infectiousness to end of infectiousness
Transmission route for diphtheria
saliva
Key measures of virulence
Ratio of cases of serious disease to those infected Case fatality rate
Reproductive number of polio
5-7
What is the incubation period for CJD
Unknown to over 60 years
What is the incubation period for SARS
1 to 10 days
Transmission route for mumps
Airborne droplet
Rt
Repro number t is index of time after initial index case after population is no longer completely susceptible
Reproductive number of mumps
4-7
Transmission route for polio
Fecal oral
VIrulence
Severity of disease after infection occurs
Key measures of infectivity
Incidence rate Attack rate
Herd immunity
Collective immunity Entire population, including those not immunized, that is protected against disease when a critical number of people have been immunized
Transmission route for pertussis
airborne droplet
False positive
Alpha error Type 1 error Test positive but not diseased
Reproductive number of flu
1-3
What is the incubation period for mumps
14 to 18 days
Reproductive number of diphtheria
6-7
Is the case-fatality rate a rate, a proportion or a ratio?
proportion
What is the incubation period for cholera
1 to 3 days
Transmission route for Measles
Airborne
Individual immunity
individuals who acquire immunity are protected against disease
Transmission route for flu
Airborne
Infectivity
Ability of an agent to cause infection in a susceptible host
R0 > 1
Infection will spread in the population Initial period of exponential growth
Pathogenicity
The ability of an agent to cause disease
Immunogenicity
Ability of an organism to produce an immune response in the host after infection which protects against reinfection with same or similar organism
Illness rate
# diseased/ #infected
What type of infections do virulent agents cause
Severe disease
R0=1
Infection will reach an endemic phase
Immunogenicity toward hep c
Poor
What is the incubation period for rabies
1 to 3 months
Key measure of pathogenicity
illness rate
WHen is case fatality used
with discrete, time limited events Outbreaks
Immunogenicity of humans toward hep b
Excellent
Transmission route for HIV AIDS
sexual parenteral
R
Reproductive number after population is no longer completely susceptible
When is an agent pathogenic
if it can cause disease
What is the incubation period for influenza
1 to 3 days
Does virulence change?
Yes as our ability to control and treat disease improves
What is the incubation period for HIV
2 to 4 weeks 3 to 20 years
What is the incubation period for chicken pox
14-16 days
How is case fatality rate different from mortality rate
mortality rate is a rate
What type of infections do agents with low pathogenicity cause
Asymptomatic or clinically inapparent
Reproductive number of measles
12-18
Reproductive number of pertussis
12-17
Reproductive Number
R0 The expected number of secondary cases produced by a single infection in a completely susceptible pipulation
Case fatality rate
proportion of deaths within a designated population of cases over the course of the disease Time is implied or described separately
R0<1
Infection will die out in the population
Section 5
(50 cards)
Herd immunity threshold of measles
83 to 94%
Transmission serial interval
Amount of time elapsed between infection from one generation to the next. Also called the generation time
Beta
Risk of transmission per contact
Herd immunity threshold of mumps
75 to 86%
Index case
the first case in a defined outbreak or epidemic that is recognized by public health authorities
Primary case
Person who first brings a disease into a group of people. Often determined in retrospect or unknown
Specificity calculation
true negative/(true negative + false positive)
When might excess cases not indicate an outbreak
change in reporting change in case definition increased awareness improved diagnosis
Carrier
Infectious, asymptomatic persons
Specificity
Probability a test correctly classifies individuals without disease as negative If everyone without disease tests negative, has 100% specificity
Most common study design in outbreaks
Case control if population is large or disease is rare descriptive case series
Two ways odds ratios are interpreted
1. Ratio of the odds of disease among exposed to odds among unexposed 2. Ratio of odds of exposure among diseased to odds among non diseased
Naturally resistant
not able to become infected because of genetic constitution
Herd immunity threshold of flu
Over 60%
Contact
An individual who has been exposed to a source of infection and who thus may be infected
When is field epidemiology conducted
in real time
Does R0 have dimensions
No
Herd immunity threshold of Polio
80% to 86%
Two steps to communicate outbreak findings
Brief public health officers Write a report with future investigations
Field epidemiology
The application of epi methods in non clinical settings to respond to unexpected health problems
Clinical onset serial interval
The average time between symptom onset in a primary case and secondary cases
Critical vaccination threshold
V=1- 1/r0 Missing vaccine efficacy
D
Duration of infectiousness per same unit time
WHen do we calculate an effective Ro
Also called R or Rt After initial index case and entire population isnt susceptible
Sensitivity
The probability that a test correctly classifies individuals with disease as positive If everyone with disease tests positive, test had 100% sensitivity
Epidemic curve
histogram of the number of cases against the time disease onset. Used to measure and track disease
R0 calculation
R0=BCD Mean number of secondary infections being transmitted by a primary case
How is clinical onset serial interval derived
from retrospective analysis of symptom onset times between primary and secondary case
Propagated source outbreak
multiple peaks. usually person to person transmission usually airborne
False negative
Beta error Type 2 error Diseased but tests negative
Steps in an outbreak investigation
1. prepare for field work 2. establish the existence of an outbreak 3. verify the diagnosis 4. choose study design 5. collect risk factor info 6. collect lab specimen 7. environmental investigation 8. make and test hypothesis 9. implement control and prevention measures 10. communicate findings
Estimation of transmission serial interval
Latency period + half of infectious period
ARI cause ___ % of hospitalizations among children
20 to 40
3 assumptions of R0
Population is completely susceptible ( number of susceptible people , S, should be much greater than number of infected people ) Population is constant N Population is well mixed/ homogenous
Identify and count cases
Case define Define population at risk Plot epi curve
Secondary Case
Cases who were infected by primary case. Same disease or strain.
C
Number of susceptible contacts per unit time
Herd immunity threshold of Diphtheria
80 to 85%
Case
An infected individual
Extended source outbreak
continuous or ongoing outbreak People exposed over time Etc. LD
When is high sensitivity important
When disease is severe
Susceptible
Able to become infected if exposed
How is risk information collected
questionnaires clinical data public health surveillance reporting systems
Outbreak control measures
Food recall Advisory to carriers Correct health procedures Prophylaxis Education
Outbreak
occurrence of disease that is greater than would be expected at a particular time and a particular place
Sensitivity formula
true positive/(true positive + false negative)
Preparing for field work
Build a team and identify responsibilities Implement regular readings Plan for early communication Research what is known about disease
Acute respiratory infection
Group of diseases that invlude pneumonia, influenza, tb, respiratory syncytical virus Leading cause of morbidity and mortality
What are the 3 factors that determine reproductive number
1. risk of transmission (infectiousness) 2. Number of susceptible people an index case comes in contact with 3. Average duration of infectivity
Confirming an outbreak
does observed cases exceed expected
Section 6
(50 cards)
Routine infection control practices
minimum level of precautions used with all patients all times handwashing gloves masks gowns eye protection
When would the clinical onset serial interval be the same value as the transmission serial interval
If transmission of infection occurs at the same time as disease onset if disease onset occurs halfway through the infectious period
When to wear gowns
during procedures or patient care when in contact with blood, body fluid, secretion, excretion Definite: contact As needed: for standard, droplet, airborne
Is negative pressure room needed with droplet spread?
No
URI viruses
Rhinovirus Coronavirus Flu Parainfluenza virus RSV Herpesvirus Adenovirus Bocavirus Coxsackivirus
Secondary resistance
develops during therapy Inappropriate treatment or nonadherence
MDR TB
Multidrug resistant Caused by bacteria resistant to standard TB drugs isoniazid and rifampin
Bacterial respiratory infections of LRI
Legionella S. pneumoniae
Primary drug resistance
caused by person to person transmission of drug resistant organisms
% of patients that complete home TB treatment
61%
Contact precautions
single room cohort room separation 3 ft PPE gown and gloves Clean hospital rooms daily with disinfectant
Classification of bacterial respiratory infections of LRI
Community acquired Hospital acquired Ayptical
URI
Of the nasal cavity, pharynx, larynx Common cold tonsillitis acute sinusitis
XDR TB
extensively drug resistant resistant to isoniazid, rifampin, fluoroquinolones and more than one of 3 second line injectable drugs
LRI
Of the trachea, primary bronchi, lungs Bronchitis Pneumonia
How many cases of flu each year
3 to 5 million
Acquisition of tb
Inhalation travel to alveoli Bacilli ingested by alveolar macrophages which may spread to other tissues
LRI viruses
Influenza Parainfluenza RSV Adenovirus Bocavirus Metapneumovirus
AIIR
airborne infection isolation room Ventilation >12 exchanges per hour mechanical or natural ventilation Air circulated through HEPA filter Negative air pressure
Natural reservoir of TB
disease tissue of human and other warm blooded animals
ARI cause ____% of all deaths among children under 5
18
secondary bacterial pneumonia
common in elderly or immunocompromised. Other bacteria invade the lungs bc immune system poor. Mort in all years. Underlying all morb and mort for disease.
Primary flu viral pneumonia
seen most often in pandemic years rapid progression to resp distress high mortality in all age groups
Airborne precautions
Airborne infection isolation room AIIR Minimal pt movement Surgical mask on patient not in AIIR
First line TB drugs
Isoniazid Rifampin Pyrazinamide Ethambutol Rifabutine Rifapentine
Is drug resistant TB transmitted differently?
No just more severe
When to wear mask or eye protection
procedures likely to generate splashes or sprays As needed for all types
Pathogenesis of TB
2 to 8 weeks of macrophages ingesting and surrounding bacilli. Cells form a barrier shell called a granuloma. If immune system doesnt work, bacilli multiply
Classification of ARI
Upper respiratory infection (URI) Lower respiratory infection
Bacterial respiratory infections of URI
Streptococcus pyogenes Haemophilus influenza
primary viral pneumonia
virus colonizes in lungs and makes pneumonia. Usually in pandemic situations. Rapid progression. Can have high mort in all, even young adults. Usually 1 or 2 days after symptom onset
Infectious period of flu
less than 1 day only 5% of cases infectious for over 3 days
Two main types of infection control practices
1. routine/ standard precaution 2. transmission based
Transmission of TB
Small droplet Expelled when cough, sneeze, speak, sing Close contact Risk factors differ for infection and disease
Risk factors for community acquired pneumonia
COPD Alcoholism Lung abcess HIV Travel IDU Etc
Incubation period of flu
1 to 4 days
Clinical presentation of flu
High abrupt fever malaise myalgia headache cough prostration
Generation time of flu
latency period times half infectious period 1.6+0.5*1 2 days
What is attact rate of flu during pandemic years
30%
When to wear gloves
contact with blood, body fluid, secretion, mucous membranes, wounds, contaminated items Definite: contact As needed: standard, droplet, airborne
When are private patient rooms suggested
Definitely for droplet, contact, airborne
Droplet procautions
Single room Cohort rooms Pt separation by 3 ft Surgical mask on pt Don PPE mask upon room entry
Mask v respirator
masks protect from splashes, body fluids, inhalation of droplets respirators needed for airborne or aerosolized pathogens
Droplet transmission
infections spread by large droplets generated by cough, sneezes etc. flu
PPE
Personal protective equipment Gloves Gowns Mask
Second line TB drugs
Streptomycin Cycloserine P-aminosalicylic acid Ethionamide Amikacin/kanamycin Capreomycin Levofloxacin Moxifloxacin Gatifloxacin
% of patients who complete DOT
86-90%
Secondary bacterial pneumonia
more common in elderly or immunocompromised patients cause of mortality in all epidemics
Cold weather and ARI
Inhalation of cool air, cool body, cold stressor cause suppression of immune responses vasoconstriction and limitation of leukocytes decreased muscociliary activity Spending more time indoors
Latency period of flu
1 to 2 days
Section 7
(50 cards)
Who should get flu vaccine
all pts 6 months old or greater unless pt has life threatening allergy to the vaccine or one of its ingredients
Surveillance systems
networks of people and activities that maintain the processes
Flu like illnesses
parainfluenza viruses rhinoviruses
Attributes of surveillance
PPV Sensitivity Timeliness Representativeness Data quality Simplicity Flexibility Acceptability
Types of flu
A B C
Active surveillance
organization conducting the surveillance collects data actively
NA
Neuraminidase in flu virus allows for viral release from host epithelial cell important for pathogenisis, immune protection, antiviral target
World flu patterns
less seasonality in tropical regions multiple strains circulate at once, first in tropical regions
Antigen
Substance or molecule that is capable of stimulating an immune response
What should surveillance systems have
Have processes and methodologies to keep sensitive data private have no barriers to info flow guide services and programs capitalize on natural experiences
1918 flu pandemic
500 million infected 10 to 20% mortality 50 to 100 million deaths
Objectives of surveillance
1. monitor occurrence 2. Provide useful info for appropriate timely ix 3. Provide indication of success of ix
IIV
inactivated influenza vaccine shot Cant cause flu soreness
Flu classifications
influenza flu like illness haemophilus influenzae bacterium
Case defintions
for surveillance balance sensitivity, specificity, simplicity costs, ftimeliness Probably, sus, confirmed Dependent on context and current needs Change over time for emerging infectious disease
How flu is named
virus type geographic region strain number year of isolation subtype
Acceptability
does effort yield info that is useful to people who need it
Notifiable diseases
national diseases that SHOULD be reported to cdc by states and jurisdictions without personal identifiers used for monitoring diseased, nationwide aggregates, identify at risk groups, forming policy
Primary objective of surveillance
monitor occurrence of disease over time where and when problems occur who is affected
Seasonality of flu
low humidity ,cold weather increase transmissibility Viral shedding greater at low temperature Droplets are more stable at low humidity
HA
hemagglutinin is part of flu virus that is an attachment protein important for pathogenisis, immune protection, antiviral targets
Flexibility
can the system readily adapt to new circumstances or changing needs
Surveillance cycle
Data collection Data integration Analysis and interpretation Surveillance Products Action* Dissemination
Simplicity
can data be accessed easily
Notifiable v reportable disease
not mutually exclusive can change reporting from care provider to state. notification from state to cdc or who
Predictor of flu severity
primary site of infection where HA protein binds
LAIV
Live attenuated influenza vaccine mist does infect host cells but doesnt cause disease easy to administer less effective
Population based surveillance
seeks to capture all occurrences or a representative sample in a defined geographic area Used to calculate incidence and prevalence includes reporting systems
Flu C
mild illness
Timeliness
how promptly does info flow thru cycle of surveillance
Positive predictive value
PPV = TP / (TP + FP) To what extent are reported cases really cases dependent on accuracy of test and disease prevalence
Flu vaccine production
3 or 4 A and B strains selected vaccine made in eggs 9 months
Triple A surveillance cycle
Assess- data generation, reporting Analyze- and interpret Action- decision
Antigenetic drift
minor antigen changes through mutations causes annual epidemics changes in HA or NA lead to no antibody protection
Flu B
exclusively in humans and seals
Flu A
causes pandemics. most virulent
Two types of flu vaccine
IIV LAiV
Flu treatment
antivirals that inhibit NA activity zanamivir oseltamivir 70 to 90% effective prophylacically must be taken within 48 hours of onset reduces severity and duration
Antigenetic shift
major genetic changes through reassortment common with viruses with segmented genomes coinfection
Flu mortality rate
0.1%
When can antigenetic shift cause pandemics
variant retains ability to replicate in humans is efficiently transmitted between humans has new surface antigens that evade existing antibodies
Efficacy of flu shot
50 to 80%
Representativeness
do events detected represent all persons in target pop
Reportable diseases
diseases of public health importance that MUST be reported to state or territorial jurisdictions by law allows contact tracing and partner notification Each state has own laws and lists
Flu surveillance
1. viral surveillance network- weekly numbers of lab confirmed in hospitals 2.mort surveillance of 122 cities weeky reporting % of deaths 3. flu associated peds deaths weekly 4. outpt services - 1800 sites weekly 5. geographic dist of flu activity
Flu transmission
person to person close contact droplet, contact, airborne transmission
Non population based surveillance
Active passive enhanced passive sentinel post marketing syndromic
Data quality
how complete are data
Surveillance
ongoing and systematic collection, collation, analysis and interpretation of health data and dissemination of results to those who need to know to avoid and prevent infections or epidemics
How many flu deaths each year
250k to 500k
Section 8
(50 cards)
Horizontal HAi reduction
reduce risk of a broad range of infections that are not pathogen specific includes -standard precaution -universal decolonization -universal gloving -cleaning
Is latency period the same length as the preinfectious period?
Ues
How many HAi deaths each year
75000
Most common HAi
Pneumonia GI (cdif) Surgical site Bloodstream infection UTI
Norovirus and Sapovirus
Noro is highly contagious Infectious dose is 18 particles 60% of all GI illness fecal oral or droplet stable and survives freezing and heating to 140 F Not killed by 70% alcohol
Can an odds ratio be used to interpret findings from cohort study?
Yes
Total cost of HAi
over 9 billion
How does length of incubation period and latency impact quarantine?
If incubation period is shorter than latent period, people start showing symptoms before they are infectious which makes quarantine effective
BRFSS
phone survey starting in 1993 Behavioral risk factor surveillance states collect data, send to cdc
Source of contact HAI
Other pt Visitor Hospital staff Reusable equipment non mobile equipment Catheter Drain
How to reduce risk of cdif
sensitive detection enhanced cleaning isolation hand hygiene
Most common HAI pathogens
Cdif Staph Ecoli
How are HAI reported
THrough CMS website
What is a practical definition for generation time
time separating onset of symptoms of infector and infectee
What is best measure of association for case control study
Odds ratio
Case fatality rate
percentage of population that dies from a specific disease
Syndromic surveillance
surveillance of health related data preceding diagnosis with a sufficiently strong signal to warrant future response Used for early detection of outbreak, monitor trends, confirm outbreaks uses existing health data in real time to provide immediate analysis ex. OTC sales, internet searches
Vaccine effectiveness in outbreak
1- attack rate vac/ attack rate unvac
Bundles
Grouping of evidence based best practices that individually improve care, but when applied together result in greater improvement
How many HAI in US each year
720000 4% hospitalized patients 25% device related
What does latent TB lack?
Sensitivity
Do vaccines only protect those immunized?
No
What is most likely reduced with DOT?
Secondary drug resistance
post marketing surveillance
monitor safety of drug or device after it is released to the market
Contact tracing
the identification and diagnosis of people who may have come into contact with an infected person
HAi
Hospital acquired infection
What are primary risk factors for cdif infection?
Recent antibiotic exposure contamination of environment
Passive surveillance
data supplied to health departments based on established rules and regulations usually undercount
Rare disease assumption
assumption that OR approximates RR
What is the purpose of statistical tests that evaluate associations?
determine if the findings are due to chance alone
Is a respirator needed to protect HCW from droplets?
no
Limitations of sentinel surveillance
not effective for rare disease wont id outside of catchment areas cant directly estimate prevalence and incidence
Source of airborne hAI
Other patients Visitors Hospital spread Environment Can be large droplets or airborne
Why is generation time difficult to measure?
Cant find precise moment of infection
Are magnitude of effect size and statistical significance equivalent?
No
When to use soap and water
hands visibly soiled or dirty, contaminated with blood or body fluid after using bathroom
Does the disease incubation period impact R0?
no
When does a zoonotic infection occur
When a virus, bacteria, fungus, or parasite crosses species to infect humans
Where do HAI microbes come from
Potable water (LD) Air Contact Self
How would you calculate generation time assuming equal transmissibility during the infectious period?
Generation time= latency period+ infectious period/2
Vaccine effectiveness in case control
1-OR
Strengths of sentinel surveillance
signal trends id outbreaks monitor changes in disease burden
Vertical HAI reduction strategies
Reduce risk of infection for specific pathogens -active screening -contact precautions -vaccination
What criteria do epis use to classify disease
reservoir of organism means of transmission
What most impacts R0?
Infectivity
What is best measure when calculating how many people have disease over 2 years
period prevalence
Enhanced passive surveillance
active follow up once a case is reported involves contact tracing for diseases like TB, STI, Ebola, to prevent transmission
Sentinel Surveillance
reporting of disease cases by select institutions or individuals useful when need high quality data not from passive system involves limited networks
When to use purell
not visibly soiled before and after pt contact after direct contact after touching equipment
Vaccine effectiveness in prospective cohort
1-hazard rate 1-relative risk 1- CI vac/ CI unvac
Section 9
(1 card)