Infectious Disease

Question 1

Sources of infection:

Answer 1

• Others humans
• Insect vectors (Lyme and Nile disease)
• Others species (rats)
• Water and food (E.coli)

Question 2

Spread of an infectious disease is multifactoriel:

Answer 2

health host, environnment, life style, genetic…

Question 3

2 ways to improve health:

Answer 3

1. Immunization and decrease the exposure

2. Improving nutrition (increase resistance)

Question 4

Steps to spread the pathogen to the host:

Answer 4

1. Recognition of specific receptor and ligand-binding in the cell (to spread the pathogen)
2. Pathogen resistant to host defense, survive and multiply and cause injury.

Question 5

When the pathogen attack the cells, our immune systems act:

Answer 5

1. Innate immunity (Complement and NK cells protect us from microbes that break through our epithelial barrier)
2. Adaptive immunity (antibodies and effector T cells)

Question 6

When antigens from microbes enter a cell:

Answer 6

1. An extracellular antigen (bacteria) will be presented on the phagocytic cell surface by MHC class II peptide.
2. It trigger production of antibodies and cell-mediated immunity

Question 7

When antigens from virus enter a cell:

Answer 7

1. An intracellular antigen (virus) will be presented on the cell surface by MHC class I peptide. (signaling the immune syst. that the cell is infected by a virus)
2. Antigen presenting cell (APC) will present the virus to Helper-T cells
3. A cytotoxic T cell will attack the virally infected cell or it will trigger the production of antibodies (B cells)

Question 8

Binding of antibodies to antigens inactivates antigens by:

Answer 8

Neutralization, Agglutination of antigen-bearing particles (microbes), precipitation of soluble antigens, activation of complement (cell lysis)

Question 9

Antigen resists defense of the host by:

Answer 9

• Antigenic variation (change and diff. type, mutation, resistance to phagocytosis)
• Inhibition of complement activation
• Antibiotic resistance
• Multiple receptor sites for the antigen
• Latent infection (eg. herpes)
• Neoplasmic transformation (eg. cancer)

Question 10

Host susceptibility increased due to:

Answer 10

Change in demographic and change behavior (travel)