Infectious Diseases

What is the definition of diseases?

A diseases is a condition that causes the body to function less effectively and produce signs and symptoms

What is an infectious disease?

It can be spread from person to person via pathogens, making them transmissable

What are examples of infectious diseases?

Influenza, HIV, pneumococcal diseases

What is a non-infectious disease?

Diseases that are not caused by pathogen, is not transmissible

Can be inherited, malnourishment, environmental factors, lifestyle choices

What are examples of non-infectious diseases?

1. Excessive alcohol consumption: liver cirrhosis

2. Excessive consumption of polyunsaturated and trans fats: coronary heart disease

3. Cigarette smoking:

4. coronary heart disease and atherosclerosis

5. Sickle cell anemia

6. Type 2 diabetes

What are the three ways of spreading infectious diseases?

1. Through droplets in the air

2. By direct contact

3. By contaminated food/water

How are infectious diseases spread through droplets in the air?

• Sneezes/coughs contain numerous tiny droplets that contain the pathogen

• When people breathe in the droplets, they get infected

What are the three ways infectious diseases are spread through DIRECT CONTACT?

1. Exchange of bodily fluids (e.g. STIs)

2. Breastfeeding (Hepatitis B, Syphilis)

3. Skin to skin*

How do pathogens enter the bloodstream of an uninfected person?

1. Through contact with mucous membrane (lining of the eye, nose and mouth)

2. Through breaks in the skin and come in contact with the bloodstream

How are infectious diseases transmitted through contamination of food/water?

Can be contaminated by the pathogens that cause cholera *when the food is not prepared properly

What are the 4 ways to prevent contamination of food/water?

1. Practice hygienic food preparation

2. Have good personal hygiene

3. Maintain a clean water supply

4. Ensure proper sewage treatment

What are 7 structures of bacteria?

1. Cell membrane

2. Cytoplasm

3. Plasmids: small circular DNA structures

4. Cell wall

5. Ribosomes

6. DNA (not membrane bound)

7. Flagellum

Are all bacteria pathogenic?

Some bacteria are pathogenic, while others are non-pathogenic

What are the 2 structures of viruses?

1. Protein coat

2. Genetic material

What are the two possible types of genetic material found in viruses?

DNA or RNA

What are the 3 characteristics of viruses?

1. Does not have cellular structures

2. Does not grow, respire, excrete

3. Can only reproduce when it enters a living cell

How do viruses reproduce?

They reproduce only when they enter a living cell → the living cell acts as a HOST as it contains the necessary materials for reproduction like enzymes and organelles like ribosomes

What are the 5 differences between bacteria and virus?

1. Outer covering:

Bacteria → cell wall, Virus → Protein coat

2. Genetic material:

Bacteria → DNA, virus → DNA or RNA

3. Cell membrane:

Bacteria → present, virus → absent

4. Cytoplasm:

Bacteria → present, virus → absent

5. Ribosome:

Bacteria → present, virus → absent

What is influenza?

A diseases that attacks the respiratory system → can lead to complications like pneumonia (lung infections)

How does the influenza virus look like?

What causes influenza?

Influenza virus

How is the influenza virus transmissed?

1. droplets in the air containing the virus

2. touches an object containing the virus

3. contaminated surface containing the virus

… and then touches mouth, eyes, nose (mucous membrane)

What are the 6 signs and symptoms of influenza virus?

1. High fever

2. Headache

3. Stuffy nose

4. Cough

5. Sore throat

6. Muscle aches

What are 7 methods to reduce transmission of the influenza virus?

1. Influenza vaccination; annual vaccination recommended

2. Avoid close contact w infected people and vice versa

3. Cover mouth and nose with tissue when coughing/sneezing and dispose properly

4. Wear surgical mask when sick

5. Wash hands with soap and water, rub with disinfectant, hand sanitiser when in contact with contaminated surface

6. Avoid touching eyes, mouth, and nose to prevent contact with contaminated object

7. Antiviral drugs prescribed by doctor

What is the pneumococcal disease?

It is a major cause of death worldwide, and attacks different parts of the body

How does the pneumococcal affect the body?

1. middle ear infection

2. lung infection

3. pneumonia

4. inflammation of membrane of brain and spinal cord

What causes the pneumococcal disease?

Pneumococcus bacteria/ Streptococcus pneumoniae

How is pneumococcal diseases transmissed?

Respiratory droplets

What are the 6 signs and symptoms of pneumococcal disease?

1. fever

2. headache

3. vomiting

4. cough

5. chest pain

6. rapid breathing

What are 7 methods to reduce the transmission of pneumococcal disease?

1. Pneumococcal vaccination

2. Avoid close contact w infected people and vice versa

3. Cover mouth and nose with tissue when coughing/sneezing and dispose properly

4. Wear surgical mask when sick

5. Wash hands with soap and water, rub with disinfectant, hand sanitiser when in contact with contaminated surface

6. Avoid touching eyes, mouth, and nose to prevent contact with contaminated object

7. Antibiotics prescribed by doctor

What is a vaccine?

A vaccine contains an agent that resembles a pathogen and prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when the pathogen invades

What is a vaccination?

The process of receiving a vaccine

What do antigens do?

Antigens are substances that trigger the production of antibodies

How do pathogens trigger the production of antibodies

Proteins on the surface of a pathogen (bacteria/virus) are antigens, which trigger the production of antibodies, hence, when they enter the bloodstream, they stimulate white blood cells to produce antibodies against them

How does a vaccine stimulate the white blood cells?

Vaccine contains an agent that resembles a pathogen, and enters the body, it stimulates the white blood cells to produce anti-bodies

How does the white blood cell help the vaccine?

1. White blood cell binds with the agent found in the vaccine

2. WBC is stimulated to divide

3. WBC produces antibodies

4. Antibodies destroy the agent in the vaccine

How do the WBC prevent future infections?

Some of the white blood cells that were stimulated remain in the bloodstream

When live pathogens enter the bloodstream, the WBC will recognise them and quickly produce the antibodies and destroy the pathogens before they infect cells

What are antibodies?

Proteins produced by the white blood cells to destroy a pathogen

What are the 5 characteristics of antibodies?

• Specific in action

• Destroy one type of pathogen (will be ineffective against another type of pathogen

• tags a pathogen for destruction by WBC

• Ineffective against viruses

• Many antibodies are chemically modified to make them more effective in treating diseases

What are antibiotics?

Antibiotics are drugs used to treat bacterial infections made by microorganisms and used to kill/inhibit growth of bacteria

How do antibiotics work?

They work by interfering with the growth and metabolic activities of the bacteria

What are the 4 cell parts antibodies inhibit?

1. Cell wall

2. Cell membrane

3. Ribosomes

4. Cytoplasm

How do antibodies inhibit the synthesis of bacterial cell wall?

Some antibiotics prevent the synthesis of bacterial cell walls

When bacterial cell walls are weakened, water enters the cell by osmosis, the cell then expands, bursts and dies

How do antibodies inhibit cell membrane function?

Some antibiotics inhibits cell membrane function by breaking up the bacterial cell membrane

Without cell membrane, the bacterial cell is no longer protected from its environment as any substance can move into the bacterial cell

How do antibodies inhibit protein synthesis in ribosomes?

Some antibiotics bind to bacterial ribosomes, preventing the ribosomes from taking part in protein synthesis and thereby inhibiting growth → protein is needed for cell growth and repair of worn out cell

How do antibodies inhibit enzyme action in cytoplasm

Bacteria require a vitamin called folic acid for growth.

Some antibiotics inhibit the enzyme needed for the synthesis of folic acid → inhibits growth of bacteria

Why can antibiotics kill bacteria and not viruses?

1. They act on bacterial cell walls, which viruses lack

2. They break up cell membranes, which viruses lack

3. They act on ribosomes, inhibiting protein synthesis and growth, viruses lack ribosomes and cannot grow

How does antibiotic resistance occur?

1. In a population of bacterial cells, some are more sensitive to a certain antibody

2. When the antibody is taken, bacterial cells that are more sensitive are killed off but bacterial cells that are less sensitive are not easily killed and may survive

3. If the prescribed course of antibiotic is not completed, the less sensitive bacterial cells that survive will multiply and increase in numbers → antibiotic resistance

What does it mean by a bacteria is more sensitive to an antibody than another bacteria?

It means that that bacteria can be killed easier by that antibody in comparison to another bacteria

What happens if the prescribed course of antibiotic is taken?

There is a higher chance that all bacterial cells are killed

What is the after-effect of antibiotic resistance?

The subsequent generations of the bacterial cells will become increasingly less sensitive to the antibiotic

Eventually, the population of bacterial cells become resistant to antibiotic A

What is the disadvantages of antibiotic resistance?

Antibiotic will not be able to kill the antibiotic-resistant bacterial cells

Other types of antibiotics will be required to treat the bacterial infection

What are superbugs?

Bacteria that are resistant to medicines like antibiotics

What are 3 ways to reduce antibiotic resistance?

1. Not misusing/overusing antibiotics

2. Completing the full course of antibiotics prescribed by doctors → ensures all bacteria is killed

3. Using antibiotics only when necessary