LECTURE 9 (Biomedical basis of public health) Flashcards
What is the history of infectious diseases?
- “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
Which public health measures conquered infectious diseases?
- Purification of water
- Proper disposal of sewage
- Pasteurisation of milk
- Immunisation
- Improved nutrition and personal hygiene
- Discovery and introduction of antibiotics in 1940s
What are the major epidemic diseases caused by?
- Bacteria
- Viruses
- Parasites
What happened in the 1880s and 1890s?
The fact that each of these diseases is caused by a specific microbe was established
What did Robert Koch do?
He developed techniques to classify bacteria by their shape and their propensity to be stained by various dyes
What is the role of Kock’s postulates?
A set of rules that could be used to prove that a specific organism caused a specific disease
What are Koch’s postulates?
- 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
What is the difference between Bacilli and Cocci?
Bacilli = bacteria that appear rod-shaped when observed under the microscope
Cocci = round-shaped bacteria
[different forms of bacteria are Bacilli, Cocci and others]
Which bacteria did Koch identify?
- Tubercle bacilli -> cause of Tuberculosis
- Vibrio cholera -> cause of Cholera
What is the history of Viruses?
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
What is the difference between Bacteria and Viruses?
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
What are the human diseases caused by viruses?
- Smallpox
- Yellow fever
- Polio
- Hepatitis
- Influenza
- Measles
- Rabies
- AIDS
- Common cold
How can human diseases also be spread apart from viruses and bacteria?
Protozoa/single-celled animals that can live as parasites in the human body
[roundworms, tapeworms, hookworms, pinworms]
How are Infectious diseases spread?
Either DIRECTLY from one person to another or INDIRECTLY by way of water, food or vectors such as insects and animals
What is the Public health approach to controlling infectious diseases?
To interrupt the chain of infection
What is the chain of infection?
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
What is a Pathogen?
A virus, bacterium or parasite that causes the disease in humans
What is a Reservoir?
A place where the pathogen lives and multiplies
[e.g rats, racoons and bats and contaminated water and food]
What is a method of transmission?
The way a pathogen travels from one host to another or from a reservoir to a new host
Even if the pathogen gains entry, why might a new host not be susceptible?
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
How do you control the spread of disease?
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
What is Epidemiological surveillance?
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
What is Quarantine?
Isolation of the patient to prevent him or her from infecting others
What is the Public health response when an outbreak is detected by surveillance?
- Locate people who have had contact with the infected individual
- Immunise them/give them medical treatment
