Infectious diseases

Question 1

Define infectious diseases

Answer 1

They can be transmitted from person to person, and they are caused by disease-causing microorganisms called pathogens, which include bacteria and viruses

Question 2

Define non-infectious diseases

Answer 2

They are not caused by pathogens and cannot be transmitted from person to person.

Question 3

How can infectious diseases be spread

Answer 3

Droplets in the air, coming into contact with body fluid of an infected person, contaminated food and water

Question 4

Describe characteristics of bacteria(1)

Answer 4

Possess cell wall, cell membrane, cytoplasm and genetic material
No nucleus or membrane-bounded organelles
Genetic material consists of circular chromosome consisting of coiled up, circular strand of DNA, may have smaller rings of DNA called plasmid
Bacterial cell wall made of peptidoglycan (sugars and amino acids) and proteins

Question 5

Describe characteristics of bacteria(2)

Answer 5

Mobile bacteria possess long thread-like structures called flagella which allow them to move either toward or away from stimuli
Bacteria have slime capsule, sticky layer of polysaccharide or protein that can help cell adherence or evasion of host’s immune system
Some are pathogenic and some are non-pathogenic

Question 6

Describe structure of virus

Answer 6

Smallest disease-causing particles known, virus always made up of genetic material surrounded by protein coat known as capsid. Some viruses surrounded by envelope derived from host cell’s membrane. Viruses usually infect specific cell types.

Question 7

Describe mode of life of viruses

Answer 7

Viruses are biochemical parasites as they take control of a living cell, known as host cell. First step involves getting genetic material of virus, together with viral proteins, across cell membrane of the host cell into the cytoplasm

Question 8

Why are viruses not considered living

Answer 8

Viruses cannot reproduce or carry out metabolic activities outside of a host cell

Question 9

What is similarity between bacteria and virus

Answer 9

Both contain genetic material

Question 10

What are differences between bacteria and virus

Answer 10

Bacteria genetic material typically DNA, virus may not be DNA. Bacteria has cell membrane, virus has protein coat. Bacteria has ribosomes while virus do not. Bacteria can reproduce itself, virus needs host cell to reproduce

Question 11

How is influenza transmitted

Answer 11

Spread from person to person through respiratory droplets propelled by coughing and sneezing. Influenza passed on through contact with contaminated surfaces.

Question 12

How to reduce transmission of influenza

Answer 12

Annual influenza vaccination is recommended to protect against influenza, especially for individuals belonging to populations at higher risk of complications of influenza

Question 13

Describe pneumococcal disease

Answer 13

Disease caused by bacterium called Streptococcus pneumonia, known as pneumococcus. Attacks lungs, blood, coverings of brain and spinal cord, middle ear

Question 14

How is pneumococcus transmitted from person to person and what are the symptoms

Answer 14

Can spread from person to person by direct contact, droplets from infected person through coughing or sneezing, articles contaminated with infected droplets
Symptoms: Fever, headache, vomiting, cough, chest pain and rapid breathing

Question 15

How to reduce transmission of pneumococcus bacteria

Answer 15

Get pneumococcal vaccination
Prompt treatment with antibiotics, especially penicillin. However, in recent years treatment has become more challenging with emergence of strains resistant to antibiotics, especially penicillin.

Question 16

What are antibiotics

Answer 16

Substances that kill or inhibit growth and replication of bacterium

Question 17

How do antibiotics target bacteria

Answer 17

Inhibit synthesis of bacterial cell wall - when cell wall is weakened, unable to resist expansion when water enters cell, hence bacterium bursts and dies
Inhibit cell membrane functions by breaking it up
Inhibit protein synthesis in ribosomes, antibodies bind to ribosomes, preventing ribosomes from synthesising polypeptide chains, inhibiting growth
Inhibit enzyme action in cytoplasm, action of enzyme required for bacterium to synthesise folic acid inhibits growth of bacterium

Question 18

Why are antibiotics not effective on viruses

Answer 18

They act on bacterial cell walls, virus do not have
They break up cell membranes, virus do not have
They act on ribosomes, inhibiting protein synthesis and growth. Viruses do not have ribosomes and do not grow

Question 19

How do antibiotic-resistant bacteria emerge

Answer 19

Antibiotic resistance occurs when bacteria develop resistance to specific antibiotics after being exposed to it. Due to variation in bacteria population, there may be bacteria which may be less sensitive to antibiotics, manage to evade action of antibiotics, especially when prescribed course of antibiotics not completed. When they survive, they reproduce and more bacteria in population are less sensitive antibiotics. Bacteria will acquire resistance to antibiotics. Drug becomes less effective or ineffective when used to treat the infection

Question 20

Define superbugs

Answer 20

‘Superbugs’ are bacteria that are resistant to many types of antibiotics. Superbugs may make it harder for doctors to effectively treat infections, leading to prolonged illness, higher healthcare costs and death

Question 21

Describe vaccine

Answer 21

Vaccine is technique used to induce immune system to develop acquired immunity to specific disease using a vaccine. A vaccine contains agent that resembles pathogen and prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when pathogen invades

Question 22

How do vaccines work

Answer 22

Substances that trigger production of antibodies are called antigens. When foreign particles such as pathogens enter bloodstream, they stimulate white blood cells to produce antibodies against them. When vaccine which contains agent that resembles pathogen enters the body, stimulates the white blood cells to produce antibodies. Antibodies are proteins that are produced to destroy pathogen. They are specific in action. Antibodies that destroy one type of pathogen will be ineffective against another type of pathogen, can tag pathogen for destruction by white blood cells

Question 23

Describe primary and secondary immune response

Answer 23

When vaccine given, white blood cells become activated and produce antibodies just as they do when they encounter actual disease-causing organism. Called primary immune response. The next time person is exposed, there will be sharp increase in level of antibodies produced, secondary immune response
As time passes, level of antibodies begins to fall, remains high only if person repeated exposed to same antigen, either by accident or booster shot. If natural exposure does not occur, amount of antibody falls slowly, reaching low unprotective level