Unit 4: Infectious disease

1. Unit 4: Infectious disease

2. Infectious Disease • The #1 cause of death and disability in the world today • Infectious diseases are not as big of a concern in developed countries such as Canada • Except in people with poor immune systems • Infants • The elderly • Malnourished people • Alcohol abusers

3. Infectious Disease • Caused by infection. • Infection = when a microorganism (ex. Bacteria, virus) invades the body which is typically accompanied by damage to cells • Invasion is followed by a latent period, which is the time between infection and the development of symptoms/signs

4. Pathogens • Pathogens are disease causing agents • Ex’s: • Viruses non-living organisms composed of DNA or RNA enclosed in a protein coat. • Require host to survive • Bacteria single-celled organisms that can live outside of the body • Fungi • Parasites (ex. Tapeworms, amoeba) • Survive by compromising host

5. Antigens • All pathogens contain antigens • Antigen = “antibody-generating” • It is a protein/sugar on a microorganism’s surface that our immune system recognizes and tries to eliminate

6. Natural Defence to infection • Skin • Cilia • Mucus • Elevated body temperature A pathogen can enter through a lesion (cut) in the skin

7. Natural Defence to infection:The Immune system • Immune system= complex system in the body that helps protect against pathogens and disease • Key immune components: • Macrophages • Antibodies • B-Cells • T-Cells • Memory B-Cells • Memory T-Cells Organs of the immune system

8. Macrophages • Macrophages (“big eaters”): a cell that surrounds and digests foreign matter Macrophage ingesting 2 red blood cells

9. Antibodies • Antibodies: Specific proteins that stick to the specific antigens of pathogens. • They cause pathogens to clump so: • they cannot enter cells • they can be more effectively excreted

10. Key immune components • B-cells: once activated, have one of 2 fates: • Become plasma cells which secrete antibodies • Become memory cells to fight off the same infection in the future • T-cells: there are several types • Helper T cells: help other immune cells • Cytotoxic T cells: destroy virally infected cells • Memory T cells: fight off the same infection in the future • Regulatory/suppressor T cells: make sure response isn’t overactive

11. Key Immune components • Memory T-cells/ memory B-cells: created the first time a certain type of pathogen enters the body while regular B-cells and T-cells are fighting infection. • The next time the same pathogen enters the body, they are already ready, waiting to eliminate that pathogen. • Therefore, the secondary response is much quicker!

12. [Ab] mg/ml serum Days

13. Immunity • Immunity refers to the ability of your body to resist infection so that signs/symptoms and disease do not develop • Ex. I already had chicken pox once, so now I am immune to it (I won’t get it again)

14. 4 Ways of Getting Immunity • Natural Immunity (occurs naturally) • Active Natural: get exposed to pathogen • Passive Natural: Fetus receives antibodies from mother • Infant receives antibodies from breast milk • Conferred Immunity (received from an outside source) • Active Conferred: vaccination (ex. A flu shot) • Passive Conferred: get antibodies • ** The Active methods are mostly permanent • ** The Passive methods are temporary

15. Transmission of Infectious Disease • Many infectious diseases are communicable, which means that they can be passed from one person to another in one of the following ways: • Direct contact • Indirect contact • Airborne transfer • Contaminated water • Vector transmission

16. Chain of Infection

17. Chain of Infection example: H1N1 Virus (swine Flu)transmission Human #1 shakes hands with Human #2. Indirect Contact Human# 1 infected Infected human #2 H1N1 virus (swine Flu) Human #1 touches nose with hand, pathogen exits NOSE Human #2 wipes mouth with hand. Pathogen enters through MOUTH

18. A little more on H1N1 • A virus consisting of viral genes that are similar to a human, a bird (avian) and 2 types of pig viruses • First identified in Mexico in April, 2009 • June 11, 2009 the WHO declared it a level 6 pandemic

19. H1N1 • Symptoms include fever, cough, sore throat, runny nose, body aches, chills, fatigue, diarrhea, vomiting • People over 60 may have some immunity to it • The effects of this recent outbreak have been relatively minor • What if the virus mutates further and it becomes more aggressive?? • This coming winter season has many health officials worried

21. Control of Infectious Disease: Personal Level • Hand washing, alcohol based sanitizers • Cover mouth/nose when you cough/sneeze • Avoid touching eyes, nose or mouth • Bug spray • Drink clean water • Stay home if sick

22. Control of Infectious disease:Community level • Pasteurization: heat-treating fluids (ex. Milk) • Antibiotics: kill microorganisms such as bacteria • Vaccination: ex. Polio, flu vaccine • Adequate housing: minimizes exposure to pathogens • Nutrition: eating well raises your immunity • Public sanitation

23. Control of Infectious Disease at Community Level:Antibiotics • Antibiotics kill or inhibit the growth of bacteria • Their discovery, specifically the discovery of penicillin (Flemming, 1928), has dramatically decreased death from infectious disease • However, natural selection (survival of the fittest) has occurred and now many bacteria that exist today are resistant to several antibiotics

25. Third world infectious disease control • Immunization (ex. giving them vaccines) • Insecticides • Clean drinking water • Public Hygiene • General economic and social development