Chapter 14

What does epidemiology mean?

Its the study of how diseases spread, how many people get sick, and how often it happens 

What does case reporting do?

Doctors report cases so we can count how many people have a disease now (incidence) and how many total people have it (prevalence)

Who gives the U.S. most of the disease information?

The CDC (centers for disease control and prevention)

What are normal microbiota (normal flora) and does it make us sick?

They are tiny living things that live in our body and no they don’t make us sick as long as everything is normal

What is the job of normal microbiota?

They help protect us by stopping bad germs from growing too much 

What is it called when good germs stop bad germs?

Microbial antagonism

What are opportunistic microorganisms?

They are germs that are usually harmless but can make you sick in certain places or situations 

Where does E.coli normally live without making you sick and what happens if it goes somewhere else?

It normally lives in your intestines (gut) and if it leaves it can cause UTIs

What is streptococcus pneumoniae and what sickness can it cause?

It’s a germ that normally lives in the nose and throat, but it can cause pneumonia 

What is a contagious disease and example?

Chicken pox and measles are a contagious disease which means its easily spreadable to other people 

What’s a non-communicable disease and what causes them?

A sickness that does not spread from person to person. Things like genes (family traits), the environment, or lifestyle cause them. 

Can you give examples of non-communicable diseases?

Heart disease, cancer, diabetes, and chronic breathing problems

What is incidence rate?

The number of new cases of a disease in a certain time

What is prevalence rate?

The number of all cases (new+old) in a certain time. It shows how long serious and long-lasting disease is in a population

What is a sporadic disease?

A disease that happens only once in a while (ex. Typhoid fever)

What is an endemic disease?

A disease that is always present in a population (ex. the common cold)

What is a pandemic disease?

A disease that spreads worldwide (ex. AIDS, sometimes influenza)

What is an acute disease?

A sickness that starts quickly and lasts only a short time (ex. the flu)

What is a chronic disease?

A sickness that develops slowly and can last for a long time (ex. TB, Hep.B, mononucleosis)

What is a latent disease?

A sickness that hides quietly in the body and “wakes up” later (ex. shingles)

What is a primary infection?

The very first sickness you get. It starts the illness

What is secondary infection?

A sickness you get after the first one because your body is already weak

What is a subclinical infection?

A sickness that hides, your body has it, but you don’t feel sick 

What are predisposing factors? Does gender affect anything?

Things that make your body easier to get sick. Yes, gender can change how sickness affects you. 

How do climate and weather affect sickness?

Some germs spread more in certain weather (like colds in winter)

What are some other things that make you more likely to get sick?

Bad nutrition, being tired, being older, lifestyle, pre-existing illness, or even treatments like chemo.

What are the 5 stages of a disease?

1. Incubation period

2. Prodromal period

3. Period of illness

4. Period of decline

5. Period of convalescence

What happens in each of the 5 stages of a disease?

1. Incubation period - no signs or symptoms

2. Prodromal period - mild signs or symptoms

3. Period of illness - most severe signs and symptoms

4. Period of decline - symptoms start to go away

5. Period of convalescence - body heals

What does incubation time depend on?

• Type of bacteria involved

• How strong the pathogen is

• How strong the hosts’ immune system is

• How many microorganisms are affecting

What do we mean by “overt signs and symptoms” during the period of illness?

It means the sickness is very clear, you can see and feel it, like fever or coughing. 

What happens to white blood cells during the period of illness?

The number of them can go up or down while fighting the germs

What are human reservoirs in disease?

• People who spread germs to others (directly or indirectly)

• Some look healthy but still spread germs are called carriers 

What are zoonoses?

• Diseases that can pass to humans (like rabies or Lyme disease)

• Can spread by eating infected meat or through insect bites

What germs can lie in soil and make people sick?

• Soil has fungi that can cause ringworm

• Bacteria like Clostridium botulinum and Clostridium tetanus come from soil and animals

How can water spread disease?

• If water has poop from humans/animals it spreads germs 

• Ex.

• Vibrio cholerae - cholera

• Cryptosporidium - diarrhea

• Salmonella typhi - typhoid fever

What is direct contact transmission?

• Spread by physical touch (kissing, touching, sex)

• Ex. staph infections, colds, hepatitis A, measles

What is indirect contact transmission?

• Spread by fomites (non-living objects)

• Ex. germs passed by sharing doorknobs, towels, or utensils 

What is droplet transmission and how do droplets spread?

• When germs spread through tiny droplets travel a short distance in the air 

• Spread through coughing, sneezing, laughing, or talking 

What are some examples of diseases that are spread by droplets and how many droplets can one sneeze make?

• Flu, pneumonia, whooping cough

• About 20,000 droplets makes one sneeze 

What is a vehicle transmission?

Transmission of disease via a medium such as water, food, or air

What is waterborne transmission? Give an example.

A spread of pathogens through water contaminated with treated or poorly treated sewage. Example : Chloera 

What are airborne transmission? Give examples

Spread of infection by droplet in nuclei in dust. Examples: fungi, staphylococci, streptococci, spores.

What is food borne transmission?

Transmission through incompletely cooked, poorly refrigerated, or unsanitary food. 

What is mechanical transmission in vectors? Give an example.

Passive transport of pathogens on insects body parts (ex. houseflies, spreading typhoid fevers, shigellosis)

What is biological transmission in vectors?

Active process: arthropod bites an infected host, ingests blood, and the pathogen reproduces inside the vector (increasing pathogen numbers)

What are healthcare-associated infections and who is most at risk?

Infections patients acquire while receiving treatment in healthcare facilities (ex. hospitals, nursing homes, surgical centers). Most dangerous in immunocompromised hosts (burns, surgical wounds).

How are HAIs transmitted, and how can they be prevented?

Transmitted by direct contact (staff to patient, patient to staff) and formats (catheters, syringes, respiratory devices). Prevention : Aseptic techniques.