Unit 4 Infectious disease Infectious Disease The 1

Unit 4: Infectious disease

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

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

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

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

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

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

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

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

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

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, waiting to eliminate that pathogen. Therefore, the secondary response is much quicker!

[Ab] mg/ml serum Days

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)

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

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

Chain of Infection

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

A little more on H 1 N 1 • 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

H 1 N 1 • 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

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

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

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

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