1. Infectious Diseases Presented by: M. Alvarez
Adapted from:M. Arias, C. Goedhart,
and M.Burke

2. What is an Infection?
A harmful invasion and spread of foreign species, or pathogen, in a host.
VIRUS
Small pox, measles, influenza, Ebola
PRIONS
Cow’s disease
BACTERIA
Tuberculosis, pneumonia, salmonella, anthrax
FUNGUS
Athlete’s foot, ring worm
PROTISTS
Malaria, toxoplasmosis, Algae

3. Infectious Agents

4. Worldwide mortality due to infectious diseases

5. Estimated number of people in the world living with HIV/AIDS in 2008

6. Spread of Disease & Transmission
Infection in one person can be transmitted to others P S T
Susceptible
Immune
Sub-clinical
Clinical
Cases
Patient “Zero” – the first case identified
Primary – the case that brings the infection into a population
Secondary – infected by a primary case
Tertiary – infected by a secondary case

7. Transmission of Pathogens
Direct contact
Indirect contacts
Air
Objects
Vectors
Many respiratory illnesses are spread through the inhalation of germs in the air and direct contact with infected saliva or mucus.

8. Routes of transmission
Direct
Skin-skin
Herpes type 1
Mucous-mucous
STI
Across placenta
toxoplasmosis
Through breast milk
HIV
Sneeze-cough
Influenza
Indirect
Food-borne
Salmonella
Water-borne
Hepatitis A
Air-borne
Chickenpox
Vector
A carrier of an infectious agent
Ex. Malaria Parasite carried
by Mosquito

9. Factors Influencing Disease Transmission
Agent
Environment
Weather
Housing
Geography
Occupational setting
Air quality
Food
Infectivity
Pathogenicity
Virulence
Antigenic stability
Survival
Age
Sex
Genetics
Behaviour
Nutritional status
Health status
Host

10. What is Epidemiology?
Epidemiology is the science of discovering causes of illness and injury in populations.
Epidemiology studies are used to control and prevent health problems.

11. Disease Patterns Endemic Epidemic Pandemic
Number of Cases of a Disease
Time
Endemic
Transmission occur, but the number of cases remains constant
Epidemic
The number of cases increases
Pandemic
When epidemics occur at several continents – global epidemic

12. Outbreak Investigation
Basic steps in an outbreak investigation:
Gather information and confirm existence of outbreak
Confirm diagnosis
3) Establish a case definition – a standard set of criteria for identifying who has the disease
4) Perform descriptive studies
5) Develop and test hypotheses
6) Implement control and prevention
7) Report findings

13. The Spread of Infectious Disease an epidemiological simulation
Objective:
This activity will simulate the spread of an infectious disease. Our simulation will show how an infectious disease can spread from one infected person to other people, who in turn infect others.
Hypotheses
1. How many people will be infected after two rounds of interactions? _______
2. How many people will be infected after three rounds of interactions?_______

14. Procedure
Obtain a cup labeled A filled with a clear solution (body fluid).  Only one person in the class will have a cup that has been “infected”. Do not drink from the cup.
In this part of the activity, you will interact with two other students. To interact with another student, pour all of your solution into your partner’s cup, then have your partner pour half of the mixed solution into your cup. Then move to another part of the classroom and interact with a second student.
Repeat step 2 with cup B, this time interacting with four students.
Your teacher or I will come around and put an “infection indicator” in your cups. If you have exchanged solutions an infected person, you are now infected and your solution will turn pink. 

15. Data Cup A Your vial # _______ Your results______ Name Vial # Dinner
1st partner
2nd partner

16. Data Cup B Your vial # _______ Your results______ Name Vial # Dinner
1st partner
2nd partner
Same from cup A
3rd partner
4th partner
Same from cup A

17. Analysis Questions Who was patient zero?______________________
How many students in the class were infected after two rounds of interactions?_____
How many students in the class were infected after four rounds of interactions?_____
Was your hypothesis correct?_________________
How many people do you think would be infected if you had ten interactions? Explain.
What kind of mathematical model best explains your data (i.e. is the pattern random, linear, etc.)?
List three infectious diseases you have heard of and how they are transmitted.
What are some ways you can prevent the spread of an infectious disease?