LECTURE 9 (Biomedical basis of public health)

Question 1

What is the history of infectious diseases?

Answer 1

• “Black Death” (Bubonic plague) wiped out 75% of the population in Europe & Asia in 14th century
• Tuberculosis -> no. 1 killer in England in mid-19th century
• Tuberculosis, typhoid, respiratory + GI diseases -> killed most people in mid-19th century in New York

Question 2

Which public health measures conquered infectious diseases?

Answer 2

• Purification of water
• Proper disposal of sewage
• Pasteurisation of milk
• Immunisation
• Improved nutrition and personal hygiene
• Discovery and introduction of antibiotics in 1940s

Question 3

What are the major epidemic diseases caused by?

Answer 3

• Bacteria
• Viruses
• Parasites

Question 4

What happened in the 1880s and 1890s?

Answer 4

The fact that each of these diseases is caused by a specific microbe was established

Question 5

What did Robert Koch do?

Answer 5

He developed techniques to classify bacteria by their shape and their propensity to be stained by various dyes

Question 6

What is the role of Kock’s postulates?

Answer 6

A set of rules that could be used to prove that a specific organism caused a specific disease

Question 7

What are Koch’s postulates?

Answer 7

• Organism must be present in every case of the disease
• Organism must be isolated and grown in the laboratory
• When injected with the laboratory-grown culture, susceptible test animals must develop the disease
• Organism must be isolated from the newly infected animals and the process repeated

Question 8

What is the difference between Bacilli and Cocci?

Answer 8

Bacilli = bacteria that appear rod-shaped when observed under the microscope

Cocci = round-shaped bacteria

[different forms of bacteria are Bacilli, Cocci and others]

Question 9

Which bacteria did Koch identify?

Answer 9

• Tubercle bacilli -> cause of Tuberculosis
• Vibrio cholera -> cause of Cholera

Question 10

What is the history of Viruses?

Answer 10

Smallpox was transmitted from a sick to a healthy person by something in the pus of the patient’s lesions -> Isolation of causative agent was unsuccessful since agent passed through finest filters and could not be observed under a microscope -> In 1935, Tobacco Mosaic Virus demonstrated nature of viruses

Question 11

What is the difference between Bacteria and Viruses?

Answer 11

Bacteria = living, single-celled organisms that can grow and reproduce outside the body if given appropriate nutrients

Viruses = not complete cells + complexes of nucleic acid and protein that lack machinery to reproduce themselves

Question 12

What are the human diseases caused by viruses?

Answer 12

• Smallpox
• Yellow fever
• Polio
• Hepatitis
• Influenza
• Measles
• Rabies
• AIDS
• Common cold

Question 13

How can human diseases also be spread apart from viruses and bacteria?

Answer 13

Protozoa/single-celled animals that can live as parasites in the human body
[roundworms, tapeworms, hookworms, pinworms]

Question 14

How are Infectious diseases spread?

Answer 14

Either DIRECTLY from one person to another or INDIRECTLY by way of water, food or vectors such as insects and animals

Question 15

What is the Public health approach to controlling infectious diseases?

Answer 15

To interrupt the chain of infection

Question 16

What is the chain of infection?

Answer 16

The pattern by which an infectious disease is transmitted from person to person is composed of:
1) Pathogen
2) Reservoir
3) Method of transmission
4) Susceptible host

Question 17

What is a Pathogen?

Answer 17

A virus, bacterium or parasite that causes the disease in humans

Question 18

What is a Reservoir?

Answer 18

A place where the pathogen lives and multiplies

[e.g rats, racoons and bats and contaminated water and food]

Question 19

What is a method of transmission?

Answer 19

The way a pathogen travels from one host to another or from a reservoir to a new host

Question 20

Even if the pathogen gains entry, why might a new host not be susceptible?

Answer 20

Because the host has immunity to the pathogen

Explanation: Immunity might develop as a result of previous exposure to the pathogen or the host may naturally lack susceptibility for a variety of reasons

Question 21

How do you control the spread of disease?

Answer 21

1) Link 1 (Pathogen): pathogen could be killed (e.g antibiotics)
2) Link 2 (Reservoir): eliminate reservoir that harbours the pathogen (e.g controlling rat populations)
3) Link 3 (Method of transmission): e.g quarantining infected individuals and hand washing
4) Link 4 (Susceptible host): resistance of hosts can be increased by immunisation -> stimulates body’s immune system to recognise the pathogen and to attack it during any future exposure

Question 22

What is Epidemiological surveillance?

Answer 22

The system by which public health practitioners watch for disease threats so that they may step in and break the chain of infection, halting the spread of disease

Question 23

What is Quarantine?

Answer 23

Isolation of the patient to prevent him or her from infecting others

Question 24

What is the Public health response when an outbreak is detected by surveillance?

Answer 24

• Locate people who have had contact with the infected individual
• Immunise them/give them medical treatment

Question 25

Where are the only two places where smallpox virus officially remains?

Answer 25

Stored in laboraties at the CDC and in a Russian lab in Siberia

Question 26

Which two countries only have Polio?

Answer 26

Afghanistan & Pakistan

Question 27

Why is Polio more difficult to eradicate than Smallpox?

Answer 27

• Many “invisible” cases of polio occur in which children are infected and spread the virus by feral-oral route, yet not show any symptoms
• Polio vaccine is imperfect and must be administered several times to be effective
• Political upheaval has interfered with immunisation campaigns in some countries