Public Health 101 Exam 2

What are the five classes of pathogens?

They are Bacteria, viruses, fungi, parasites, and prions

How are pathogens transmitted?

Routes, reservoirs, and the chain of infection

What is the Host defense?

An Innate barrier and adaptive immunity

Majors diseases are

Respiratory, enteric, vector-borne, and STIs

How can you prevent them?

Vaccines, hygiene, sanitation, and therapy

What are emerging threats?

Zoonoses, AMR, and Climate-driven spread

Bacteria

Single-celled prokaryotes. It cause strep throat, TB, and cholera. that can be treated with antibiotics

Viruses

Obligate intracellular parasites; hijack host machinery. It causes Influenza, HIV, SARS-CoV-2. Can be treated with Antivirals + vaccines.

Fungi

Yeasts and molds; mostly opportunistic, striking immunocompromised hosts.

Candida

a type of yeast that naturally lives on the skin and inside the body. It causes no harm to the body.

Aspergillus

mold species found worldwide in soil, decaying organic matter, dust, and building materials. typically harmless but can cause illness.

Parasites

Protozoa and helminths with complex life cycles. Such as Malaria, giardiasis, schistosomiasis.

Prions

Misfolded proteins that template misfolding in neurons. It is Rare, untreatable, and most of the time fatal.

Route of exposure- Bacteria

Inhaled droplets and aerosols, contaminated food and water, direct contact with skin or wounds, and insect bites.

Route of exposure- Viruses

Respiratory droplets and aerosols, fecal-oral spread, blood and body fluids, sexual contact, and animal or insect bites.

Route of exposure- Fungi

Inhaled environmental spores from soil, dust, or decaying matter, plus skin contact and overgrowth of existing flora.

Route of exposure- Parasites

Insect vectors such as mosquitoes and ticks, contaminated water or undercooked food, and skin penetration by larvae.

Route of exposure- Prions

Ingestion of infected nervous tissue and rare iatrogenic exposure via contaminated instruments or transplanted tissue

Examples of an outbreak- Bacteria

Listeria outbreak

Examples of an outbreak- Viruses

Measles outbreak

Examples of an outbreak- Fungi

Candida auris, a drug-resistant fungus

Examples of an outbreak- Parasites

Cyclosporiasis outbreak (happened this summer with lettuce)

Examples of an outbreak- Prions

Bovine spongiform encephalopathy (BSE); Uk 1980-90s (Mad Cow Disease)

Transmission of infections

1- the reservoir

2- Portal of exit

3-Mode of spread

4- Portal of entry

5- Susceptible host

Transmission of infections- the reservoir

Where the pathogen lives and multiplies — humans, animals, soil, water.

Transmission of infections- Portal of exit

Respiratory droplets, feces, blood, skin lesions.

Transmission of infections- Mode of spread

Direct contact, airborne, vehicle (food/water), or vector (mosquito, tick).

Transmission of infections- Portal of entry

Mucous membranes, broken skin, ingestion, injection.

Transmission of infections- Susceptible host

Age, nutrition, immune status, and prior exposure decide the outcome.

What can you do to stop the transmission?

Break any single link between the 5 chains

What is an example on how to stop the transmission?

masks, chlorination, bed nets, and vaccination.

What are the types of immune defense

Innate and Adaptive

What are the types of immune defense- Innate

Immediate, non-specific, no memory:

-Skin, mucus, stomach acid, and normal flora block entry

-Macrophages and neutrophils engulf invaders

-Inflammation and fever slow pathogen growth

-Complement proteins lyse bacterial membranes

What are the types of immune defense- Adaptive

Slower, highly specific, remembers:

-B cells produce antibodies that neutralize and tag pathogens

-Helper T cells coordinate the response

-Cytotoxic T cells destroy infected cells

-Memory cells enable faster recall — the basis of vaccines

Where are infections hitting the hardest?

-4 major disease groups drive the most global infectious burdens: respiratory, enteric, vector-borne, and sexually transmitted.

-60% of emerging human pathogens are zoonotic

-1.3 million deaths each year are directly attributable to antimicrobial resistant bacterial infections

- The best prevention tool is vaccinations

Vaccination

Trains memory immunity and, at high coverage, protects the unvaccinated through herd immunity

Water & sanitation

Safe water, sewage treatment, and food safety remove the entire transmission route.

Hygiene & barriers

Handwashing, masks, and bed nets interrupt contact and vector spread cheaply.

Surveillance

Case reporting and genomic tracking detect outbreaks while they are still containable.

Why the problem is not solved yet

-Antimicrobial resistance

-Zoonotic spillover

-Climate and mobility

-Vaccine hesitancy

Antimicrobial resistance

Overuse in medicine and agriculture selects for resistant strains faster than new drugs arrive.

Zoonotic spillover

Land-use change and wildlife trade push animal pathogens into human populations.

Climate and mobility

Warming expands mosquito and tick range; air travel converts local outbreaks into global ones.

Vaccine hesitancy

Failing coverage restores diseases such as measles that were once near elimination.

Indoor air shapes exposure risk- Shared air

People can inhale infectious respiratory particles indoors. If a room has better ventilation it can reduce indoor transmission risk.

Prevention addresses different parts of risk

Reducing exposure- Ventilation and indoor air quality can reduce the chance of inhaling infectious particles.

Reducing severe outcomes- Vaccination protects against severe disease and death.

Social conditions shaped unequal risks- Barriers and solutions

-Work constraints so flexible leave might be an option

-Crowded housing so a safer shared space might be an option

-Care access so accessible services might be an option

-Language barriers exist so having a trusted person to translate is an option

The performance of a vaccine depends on the measured outcome

An infection after vaccination does not, by itself, show whether protection against severe illness failed.

-One set of outcomes to study. Effectiveness can change over time.

- Different outcomes can happen depending on the vaccines provide protection against them.

DId the Covid-19 pandemic affect mental wellbeing

Yes there was 25% Global rise in anxiety and depression prevalence in the first pandemic year. As Isolation, grief, and financial worry added pressure as access to care suffered.

why is clear communication important?

It minimizes uncertainty an it makes things more understandable

When working on messaging you might want to

-Engage with different communities

-Address uncertainty immediately with transparency

- Have a unified message

- Work on your message framing

Essential services need protection during a crisis

Disrupted care can add to the pandemic's burden

Preparedness requires sustained investment

-Readiness

-Shared responsibility

-Equitable protection

-Adaptation

Long Covid

-A chronic condition that can last for 3 or more months

-Some symptoms are: Fatigue that disrupts daily life, Difficulty thinking or concentrating, Shortness of breath, and Symptoms that worsen after effort.

Long Covid's effect on someone's daily life

they may limit school, work, and everyday activities. Some people may experience disabilities.

Pattern to action

1- Describe: Who? Where? When?

2- Measure: How much? How fast?

3- Compare: What differs?

4- Investigate: What is the explanation?

5- Act: What changes the risk?

Epidemiology turns population patterns into prevention

-Study: Ask a precise question

- Distribution: Describe person, place, or time

-Determinants: Compare exposures and outcomes

-Application: Use evidence to reduce harm

What reveals the size of an association

Comparison

Make the problem visible before explaining it

-Who is affected? (Person)

-Where does it cluster? (Place)

-When does it rise or fall? (Time)

Incidence versus Prevalence

Incidence tracks entry; prevalence captures the pool

Description versus comparison

Description generates hypotheses; comparison tests them

-If there is no comparison you can still describe a pattern but you cannot estimate an association.

Study designs

-Cross sectional

-Case control

-Cohort

-Randomized trial

Cross sectional

-What is happening now?

-Snapshot

-Fast and is prevalent

-Temporality is unclear is an issue

Case-control

-What exposures differ by outcome?

- Looks back

- Efficient for rare outcomes

-Recall/selection bias is an issue

Cohort

-What outcomes follow exposure?

-Follows a group

-Has direct incidence and temporality

-Time and attrition is an issue

Randomized trial

-What changes after assignment?

- Assign and follow

-Strong casual leverage

- Ethics and feasibility is an issue

An association can be real without being causal

-Chance

-Confounding

-Bias

-Temporality

Chance

Could random variation explain the estimate?

Confounding

Is a third factor linked to both exposure and outcome?

Bias

Did selection or measurement create distortion?

Temporality

Did the exposure clearly precede the outcome?

Is Statistical significance the same as practical importance

No it's not

Surveillance is a loop not a database

It's a constant circle of detecting, verifying data, analyzing data, deciding what to do, and then acting on it

Outbreak investigations are systematic, not strictly sequential

1- Confirm: Prepare, establish outbreak, and verify a diagnosis

2- Define: Build case definition + find and record cases

3- Describe: Analyze time, place, person, and generate hypotheses

4- Test: Evaluate hypotheses & reconcile lab/environment evidence

5- Control: Implement measures, maintain surveillance, and communicate

Does epidemiology identify the vehicle before the contamination point

Yes

Connecting biological risk to public-health action

1- Distinguish: genetic disease pathways

2- Explain: inheritance and screening

3- Connect: genes, environment, and time

4- Apply: three levels of prevention

5- Evaluate: ethics and health equity

Health risk is an interaction not a genetic verdict

-Genes: Variants and family history

-Environment: Exposures, resources, policies

-Time: Development, aging, cumulative risk

Genetic conditions arise through four distinct pathways that result in DNA change

-Single Gene: One gene has a large effect like sickle cell disease

-Multifactorial: Many variants, environment, Diabetes, heart disease

-Chromosomal: Number or structure changes Example: trisomy 21 (Down syndrome)

-Acquired: DNA changes during life Example: many cancers

If something is inherited does that mean someone is bound to get it?

No

Sickle Cell

makes blood cells sickle (crescent like) which can obstruct blood flow and break down early it can cause pain, anemia and organ damage. It also alters hemoglobin. It can be caught due to a screening and then the treatment is specialty care, prevention, family support.

What is the normal chromosomal count?

46

Numerical anomalies change the chromosome count

Trisomy 18: 47 chromosomes +18

Trisomy 13: 47 chromosomes +13

Turner syndrome: An X chromosome is missing or altered

Klinefelter syndrome: Has an additional X chromosome

Trisomy

+1 chromosome

Monosomy

-1 chromosome

Structural anomalies rearrange chromosome segments

-Deletion

-Duplication

-Inversion

-Translocation

-Ring Chromosome

Deletion

A segment is missing

Duplication

A segment is copied

Inversion

A segment reverses direction

Translocation

A segment moves to another chromosome

Ring Chromosome

Chromosome ends join into a ring

Type 2 diabetes emerges from genes, environment, and time

Inherited susceptibility + Life Context & Behavior + Age & Cumulative risk = Type 2 diabetes risk

Type 1

Autoimmune- The immune system destroys insulin-producing beta cells.

Type 2

Insulin Resistance- Cells respond poorly to insulin; the pancreas may eventually fall behind.

Lung cancer develops through acquired mutations over time

1- DNA Damage

2- Growth control fails

3- Clone expands

4- Tumor forms

Chemical mutagens damage DNA through several mechanisms

A mutagen increases the chance that DNA damage becomes a permanent sequence or chromosome change.

1. DNA Adducts

2. Base Alkylation

3. Crosslinks + Breaks

Chronic diseases

-74% of deaths worldwide are from chronic diseases

- 6 in 10 adults live with a chronic disease

-4 in 10 live with two or more

What is a chronic disease?

-A disease that persists and requires ongoing management

-A condition is broadly considered chronic when it lasts at least one year

- Limits activities of daily living

-Also known as long-term

-However chronic doesn't mean untreatable

Examples are Heart disease, diabetes, cancer, arthritis, and asthma

What is a short-term disease?

-Often begins suddenly and resolves in days or weeks

-Also known as acute

Examples are the flu, minor injury, and short-term infection

Management matters for chronic diseases

Treatment, healthy behaviors and supportive environments can control symptoms, prevent complications and improve quality of life.

Major chronic diseases share a common risks

tobacco, unhealthy diet, Physical inactivity, Harmful alcohol use Air pollution, and Genes family history. Cardiovascular, cancer, diabetes, and chronic respiratory all share most of these risks