definitions of the above terms...

review question:
describe three requirements
​for an eradication
campaign to be successful.

review question:
how does an emerging disease differ from a
re-emerging disease? 

give an example of each.

so let's talk ethics...!

source

the epidemiological triangle
​ in action

clinical epidemiological goal:
surveillence, prevention  and control of HAIs

disease reservoir:
where a pathogen lives
​and multiplies

disease source:
where the pathogen is transferred to a host

 transmission:
 how the pathogen moves from the source to the host

epidemiological challenges per stage:
1. long incubation period much harder to track (HIV)
2. infectious while asymptomatic (chicken pox)
3. may be subclinical but highly infectious (polio)
4. relapse occurs if patient ceases medication feeling better
5. pathogen can remain dormant w/ host asymptomatic (typhus) 

a cornerstone of public health, national disease surveillance requires the continuous and systematic collection, analysis, and interpretation of health data.

​this data is used to dictate disease prevention and control efforts.

Our CDC's National Notifiable Diseases Surveillance System (NNDSS)
​plays a key role in data collection across the country. 

review question:
explain the chain of infection.

keeping an eye on:

emerging diseases

such as:
SARS, MERS, Ebola, Chikungunya, Avian flu, Swine flu, Zika, COVID-19, HIV, and new variant of Creutzfeldt–Jakob disease

these infections that are new in a population or are rapidly increasing in incidence and/or geographic range. 

causes:
evolution of pathogens
 human behavior and practices, population growth
 migration
international travel
 poverty

 war
the destruction of ecosystems  

reemerging diseases

such as:
Malaria, Tuberculosis, Cholera, Pertussis, Influenza, Pneumococcal disease, and Gonorrhea

these diseases have reappeared after a significant decline in incidence or were thought to be controlled/extinct in a particular area or population. 

causes:
evolution of antimicrobial resistance
 collapse of public health systems
changes in ecology/environment

Dr. Semmelweis had a hard time after publishing his hand washing protocol and emphasizing the importance of cleanliness. His claims were thought to lack scientific basis since he could offer no  explanation for his findings.

review question:
compare epidemic, pandemic, endemic and sporadic disease.

in epidemiology...
 endemic diseases:
constantly present and predictable in a specific region or population
sporadic disease:
 occurs infrequently and irregularly showing no discernible pattern.

remember Dr Semmelweis?
​1840

 Mary Mallon was a cook for wealthy families in NYC. 
She was nicknamed "Typhoid Mary" because she was identified as an asymptomatic carrier of the typhoid bacterium, Salmonella Typhi.
Mary was responsible for several outbreaks of typhoid fever between 1900 and 1907. 
Mary spread the disease by contaminating food
due to improper hygiene.
Mary was forcibly quarantined, spending the rest of her life (30 years) on an island in the East River. 
It is estimated that Mary infected between upwards of 122 people with 3 confirmed deaths

epidemiology
is the study of how diseases are distributed within populations and the factors that influence their occurrence

review question:
explain the process by which  bacteria develop antibiotic resistance.

     epidemiological triangle

review question:
​how would you describe in your words the role of our public health system?

how is correlation different from causation

can you think of ways HAIs can spread?

national surveillance system

informed consent
w/out enticements!

confidentiality

​first do NO harm

the 5 stages of an infectious disease
1. incubation:
period between initial exposure to a pathogen and the appearance of symptoms. pathogen multiplies within the body
 
2. prodromal
vague, non-specific symptoms that signal the onset of illness
 before the specific symptoms of the disease appear 

3. illness:
infection-specific signs and symptoms of the disease are present
and the person is typically ill 

4. decline:
start of body's recovery as the immune system starts to eliminate the pathogen and symptoms begin to subside
 
5. convalescence:
body recovers fully and normal state of health resumes
note: some diseases may cause permanent damage

review question:
clinical epidemiologists work to do what?

chain of infection

        let's talk the role of               public health

    investigate
                  diagnose

                              prevent or                                     reduce  

public health problems

The United States Agency for International Development (USAID) Global Health program WAS
a key component of the U.S. government's efforts to improve health outcomes worldwide. 
its mission...
 strengthen health systems in developing countries
prevent and treat infectious diseases, such as HIV/AIDS, malaria, and tuberculosis. 
 promote maternal and child health, including access to quality prenatal care, childbirth assistance, and vaccinations. 
 respond to global health emergencies, such as pandemics and natural disasters. 
 invest in research and development of new treatments and vaccines for infectious diseases. 

 direct contact

2. indirect contact:
contact with contaminated objects, surfaces, or vectors

review question:
what is meant when a disease is eliminated?

     *prevalence is total cases of a disease in a given population                                divided by the total given population

antibiotic resistance 

occurs when bacteria evolve and develop the ability to withstand antibiotics.
infections become harder to treat and may lead to severe infections

review question:
compare communicable
​vs noncommunicable disease.

btw

 epidemiology in a clinical setting

review question:
list the six categories of pathogens and give an example of a disease each can cause.

goals of epidemiology
1. describe the nature, causes and extent of diseases in populations
2. intervene to protect and enhance the health of populations

public education
understanding bacterial drug resistance
and the abuse of anti-biotics

promoting vaccination

pre-natal/neonatal care & breastfeeding

STD education

​promoting public health
​to decrease co-morbidities

​can you think of another?

     *mortality is death   

 the process by which a pathogen spreads
               from one host to another
1. infectious agent
2. reservoir
3. portal of exit
4. mode of transmission
5. portal of entry
6. susceptible host

an endogenous source
originates within the body
ex: your gut your bacteria/fungi can become invasive and cause infection under certain conditions.

 an exogenous source originates
 outside the body
ex:
external pathogens or environmental toxins

vector control
mosquito control/spraying and reducing and standing water

understanding and implementing biopesticides like larvicides

     *morbidity is the rate of disease in a population

review question:
compare acute
vs chronic disease

  German physician Robert Koch was one of the founders of bacteriology. He discovered the anthrax disease cycle and the bacteria responsible for tuberculosis and cholera.
​Dr. Koch received the Nobel Prize for Physiology or Medicine in 1905 for his research on tuberculosis. 

review question:
​describe the 5 stages of infectious disease.

what is a challenge epidemiologists may face with one of these stages?

HAI = hospital aquired infections

       a model used to understand and                      address disease outbreaks
  by examining the interactions between:
1. an agent (the "what" of the disease)
2. a host (the "who" affected)
3. the environment (the "where" & "when" of the disease). 

review question:
​offer four ideas as to how we might break the epidemiological triangle as it pertains to a
re-emerging disease.

review question:
​explain how correlation differs from causation.

​offer an example.

review question:
​how do asymptomatic carriers of disease differ from chronic carriers?​

 indirect contact

the six main categories of pathogens are:

bacteria:
single celled microbes 
pneumonia, strep throat, food poisoning 

viruses:
require a host cell to replicate
 common cold, influenza, measles 

fungi:
 yeasts and molds

athlete's foot, ringworm, systemic infections

protozoa:
 single celled eukaryotes
 malaria, giardiasis. 

helminths (parasitic worms):
multicellular parasites
 roundworms, tapeworms, flukes

pinworm, tapeworm

prions:
 infectious proteins
​  neurodegenerative diseases   

identifying disease

 eradication = the disease has been completely eliminated from the world
elimination = the disease is  absence in a specific region or country

section 3 assessment
Monday 3/31

quarantine
understanding its use and effectiveness

public quarantine policy

entry point screening

asymptomatic carriers harbor a pathogen, do not exhibit any symptoms of the disease, but can still transmit it to others
​
chronic carriers showed disease symptoms and remain infected and capable of transmitting a pathogen for extended periods.

1890 = germ theory

infectious disease and

epidemiology

review question:
​explain how Koch's postulates shows the causality between a microbe and disease.

review question:
​public health workers focus on three areas when collecting epidemiological data.
​Describe them.

review question:
how would you define what a population is as it relates to epidemiology?

mechanical v biological disease vector

​promoting equity in public health is an ethical imperative 

review question:
​define:
endogenous source
exogenous source
indirect contact
​direct contact

diseases can be:
emerging =
new infections

 re-emerging =

previously controlled
but reappearing after
​ a period of decline

1. direct contact:
physical contact between an infected person and a susceptible person

Dr. Semmelweis was not taken seriously when he suggested hand washing might be life saving. Why?

HHS governs all of the departments of our public health services

review question:
​explain the purpose of the epidemiological triangle.

most common and worrisome HAIs:

C. difficile
UTIs
​surgical wound infection

MRSA
(methicillin resistant staph aureus)
​
pneumonia 

     *incidence = all new cases of a disease
​                              divided by susceptible population

                                                  Koch's postulates:
                                            criteria used to establish
                                                        causality
                                       between a microbe and a disease

1. the microbe be present in all cases of the disease
2. the microbe must be isolated and grown in pure culture
3. the microbe must cause the disease when introduced to a healthy host
4. the microbe must be be re-isolated from the infected host

modes of transmission:

Diseases that have been
eradicated
globally include:

***Smallpox: Eradicated in 1980
Rinderpest (cattle plague): Eradicated in 2011 

Diseases that have been
eliminated
in specific regions or countries include:

1. Congenital rubella syndrome (group of birth defects that occur when a pregnant woman is infected with the rubella virus during the first trimester of pregnancy) : Eliminated in the United States 

2. Polio: Eradicated in the Americas in 1994, and globally in 2020 
(as of 2023, wild poliovirus is still present in two countries: Afghanistan and Pakistan.
 All other countries have been declared polio-free. 
In 1988, the World Health Organization (WHO) launched the Global Polio Eradication Initiative.
 The initiative has been successful in reducing the number of polio cases > 99%. 
Vigilance is needed to maintain polio eradication in polio-free countries
and to eliminate WPV in Afghanistan and Pakistan.
Polio could re-emerge. 

3. Measles: Eliminated in the United States in 2000
thanks to the highly effective MMR vaccine but because measles is so contagious, at least 95% of a community must be vaccinated to prevent outbreaks.
the current US vaccination rate is 91%.

4. ​Rubella: Eliminated in the United States in 2005 
 controlled b y the MMR vaccine so as vaccination rates drop...

5. Guinea worm disease: nearly eradicated with only one case reported in 2023 

review question:
what is meant when a disease is eradicated?

eradication efforts require:

humans as the only reservoir
effective interventions (vaccine or antibiotic)
accurate diagnostics
life-long immunity
understanding the pathogen's life cycle/transmission
political commitment
public support/trust
economic resources
 access to healthcare
 buy in from governments

collecting and assessing  epidemiological data

opportunistic            vs              true pathogens

     *a population is any defined group of people

HAIs can be localized or systemic

 how are diseases eradicated?
eradication = complete elimination
of a disease from the global population:
new cases and chances of re-emergence are reduced to zero

5% of hospital patients are infected during their stay 

review question:
​what is an HAI? 

                                             goal:
    quantify health events in populations, focusing on:
  1. frequency (incidence and prevalence)
  2. association (risk and odds ratios)
  3. potential impact (mortality and morbidity)

review question:
explain the purpose of the National Surveillance System.

etiological
​ agent 

not anymore!

  epidemics
are disease outbreaks that occurs within a specific geographical area
pandemics

occur if the disease spreads to multiple areas or the entire planet

diseases can be:
communicable/infectious
caused by pathogens that can be transmitted person to person/animal to person

non-communicable/chronic
not contagious and caused by non-infectious factors like genetics, lifestyle, and environmental factors 

 correlation : does not automatically mean that the                             change in one variable is the cause of                             the change in the values of the other                                variable
causation : one event is the result of the occurrence                       of the other event   

review question:
explain the difference between an emerging and a re-emerging disease?

review question:
what is epidemiology and what are its two goals?

diseases can be:
acute: 
severe and sudden onset
influenza, asthma attack

 chronic:
long-developing syndrome
 osteoporosis, asthma

how can we
​BREAK 

the triangle to improve public health?

review question:
how do opportunistic pathogens differ from true pathogens?