Diseases- Validation

What is a pathogen?

A pathogen is a microorganism (a tiny living thing) or an agent that can cause disease in its host (like a human, animal, or plant).

Name the 5 types of pathogens

Virus, bacteria, fungi, protozoa, helminths (parasitic worms)

Virus

Pathogens that are about one hundred times smaller than bacteria

Can only grow and reproduce in host cells

Not considered living

e.x Common cold, Flu, Chickenpox, COVID-19

bacteria

Unicellular microorganisms that can reproduce quickly.

Causes disease in animal or human

Types- Infectious disease( can spread), Contagious disease( easiest to spread)

e.x Strep throat, Tuberculosis (TB)

fungi

Organisms like yeasts and molds. They often cause infections of the skin, hair, and nails.

Spread using spores

Need warm/moist environment to grow 

Are contagious

e.x Athlete's foot, Ringworm

protozoa

unicellular eukaryotes (cells with a nucleus) that are parasitic. They often need a "vector" to spread.

Infect blood and body of host

Live on or on their host

e.x malaria

helminths

large, multicellular organisms that live inside a host (like humans) and take nutrients from them, often causing disease as they feed off their host.

e.x roundworms, tape worms

what’s a communicable disease

Illness caused by pathogens that can spread from one person, animal, or object to another.

direct contact

physical contact between an infected person/animal and a susceptible person. This can be skin-to-skin contact, kissing, or sexual contact.

• Description: The pathogen transfers immediately from the source to the host.

• Example: Diseases like Scabies (mites), Ringworm (fungus), or Mononucleosis (kissing disease) spread by touching an infected person or their saliva.

indirect contact

Occurs via an intermediate object contaminated with the pathogen.

• Description: An infected person coughs, sneezes, or touches a surface, and then a healthy person touches that surface and transfers the pathogen to their mouth, nose, or eyes.

• Example: Catching the Common Cold or Influenza after touching a contaminated doorknob, phone, or desk that an infected person used.

ingestion

occurs by consuming a pathogen, through contaminated food or water, materials.

• Example: Cholera (from contaminated water) or Salmonella (a type of food poisoning) are classic examples of ingestion transmission

transfer of bodily fluids

occurs when contaminated bodily fluids or blood from an infected person enters the body of a susceptible person.

• Description: This typically happens through unprotected sexual contact, sharing contaminated needles, or from a mother to a baby during childbirth or breastfeeding.

• Example: HIV (Human Immunodeficiency Virus)

infection by droplets

Bacteria or viruses expelled from the body, which are released into the air.

• Description: When an infected person coughs, sneezes, or talks, they release droplets containing the pathogen and hit another person's mucous membranes (eyes, nose, mouth).

• Example: The Flu (Influenza) and some cases of the Common Cold are spread when you are in close proximity to a person who coughs or sneezes.

airborne transmission

Transmission occurs through very small, light particles that remain suspended in the air for long periods and travel over long distances.

• Description: Unlike droplets, these microscopic particles can stay floating in the air for hours and can be breathed in by a person who is not even near the original source.

• Example: Measles spread via the airborne route.

vector transmission

occurs when a living organism, carries a pathogen from an infected host to another susceptible host. The vector itself is not the cause of the disease but the carrier.

• Description: The vector, such as a mosquito, feeds on an infected animal or person, picks up the pathogen, and then transmits it to a healthy person through a bite.

• Example: Malaria

r-naught value

the average number of new infections caused by one infected person in a population that is completely susceptible to the disease (meaning no one has immunity)

importance of r-naught

for predicting an epidemic's potential and for planning effective public health interventions.

Predicts Outbreak Potential and Speed

Determines the Herd Immunity Threshold (HIT)

Public health experts can design targeted strategies

r-naught smaller than one

Each existing infection causes, on average, less than one new infection.

epidemic potential: The disease will decline and eventually die out.

r-naught equals one

Each existing infection causes exactly one new infection.

epidemic potential: The disease stays stable (endemic) but does not grow into an epidemic.

r-naught is more than one

Each existing infection causes more than one new infection.

epidemic potential: The disease will spread exponentially (an outbreak or epidemic).

hygiene measures

routine personal and environmental practices focused on cleanliness to directly remove or destroy pathogens.

examples: washing hands with soap and water or using alcohol-based sanitizer to eliminate microorganisms.

Practices to prevent contamination and growth of pathogens in food. Washing raw produce, cooking meat to the correct temperature, and avoiding cross-contamination between raw and cooked food.

physical measures

These measures physically separate people or pathogens, creating barriers that directly block transmission pathways.

Physical Distancing: Increasing the space between individuals to prevent direct droplet transmission.

Isolation & Quarantine: Separating infected or exposed individuals from the general population to break the chain of transmission.

public health measures

actions implemented by governments and health organizations to protect entire communities.

e.x Vaccination: Inducing immunity in a population to prevent infection and establish Herd Immunity.

Travel Restrictions: Limiting the movement of people across borders or regions to contain a disease geographically.

what’s a vaccine?

A product, often containing weakened or dead viruses or antigens, that trains the body to fight a specific infectious disease.

how do vaccines work?

it trains the body's immune system to recognize and fight a specific pathogen (like a virus or bacteria) without causing the actual illness.

name the 4 types of vaccines

live attenuated, inactivated, toxoid, sub-unit

live attenuated

uses a weakened or weakened form of virus or bacteria to trigger a strong and long-lasting immune response that mimics a natural infection. e.x measles vaccine

inactivated

a killed version of the pathogen, (the virus or bacteria cannot cause disease). e.x influenza

toxoid

inactivated version of a bacteriums toxin to stimulate an immune response and prevent the disease. e.x tetanus vaccine

sub-unit

only purified, specific pieces of a pathogen, such as proteins, sugars, to trigger an immune response. e.x covid-19 vaccine.

how do vaccines provide immunity to disease?

imitates an infection to engage the body’s natural defences. help the body learn how to defend itself from disease without the dangers of the whole infection.

herd immunity

indirect protection from an infectious disease that occurs when a sufficient percentage of a population has become immune.

When a large proportion of individuals are immune, it significantly reduces the probability of disease transmission from person to person. The pathogen struggles to find susceptible hosts, effectively breaking the chain of infection and making it difficult for an epidemic to start or spread.

4 reasons why people don’t get vaccinated

Misinformation and mistrust, fear of side effects, cultural or religious beliefs, access and convenience barriers