1. Communicable Diseases

2. Figure 2.10: The Burden of Disease by Group of Cause, Percent of Deaths, 2001 Data from Lopez AD, et al Global Burden of Disease and Risk Factors. Washington, DC and New York: The World Bank and Oxford University Press; 2006:8.

3. Table 2.5: The Ten Leading Causes of Death in Children Ages 0-14, by Broad Income Group, 2001 Adapted with permission from: Lopez A, Begg S, Bos E. Demographic and Epidemiological Characteristics of Major Regions, 1990-2001. In: Lopez A, Mathers C, Ezzati M, Jamison D, Murray C, eds. Global Burden of Disease and Risk Factors. Washington, DC and New York: The World Bank and Oxford University Press; 2006:70.

4. Key Terms Communicable diseases includes: – Those caused by infectious agents, such as: Malaria HIV/AIDS TB Cholera – Those caused by parasites, such as: Hookworm Filariasis

5. Studying Communicable Diseases Many aspects to the study of communicable diseases – Infectious organism and its transmission vector Life cycle and reservoir (where it lives) of the infectious organism/parasite and/or transmission vector Cycle of infection – Human to human; host to insect to human… – Pathology of the organism in the body – Diagnosis – Treatment – Prevention

6. Modes of Transmission Direct contact - person to person – Contact with an infected skin lesion – Contact with blood or other body fluids Contact with fecal material of a sick person and then touch your eyes, nose…. – Breathe in droplets expelled by coughing/sneezing sick person (some consider this airborne) – Sexual contact – Needle sharing

7. Modes of Transmission Airborne – Pathogen is aerosolized, attached to dust…in the air – Become infected by breathing in the infected air – Isolation of the infected individual is recommended to prevent transmission – Examples: SARS (TB, influenza)

8. Modes of Transmission Vector-borne – Spread by an animal - often by the bite of an infected insect Rabies – animal bite Malaria – mosquito Lyme disease - ticks Dengue fever – mosquito – Insect itself is often infected by biting an infected carrier Rodent with plague  tick  human Livestock with African sleeping sickness  tsetse fly  human

9. Modes of Transmission Food and water borne – Infection occurs with ingestion of contaminated food or water Water borne: – Cholera – Hepatitis A Food borne – often fecally contaminated or contaminated water used to cook foods – Salmonella – E. coli

10. Modes of Transmission Mother-to-child (MTC) – Referred to as vertical transmission – Infection is passed from mother to fetus during pregnancy or mother to infant through breast milk

11. More Key Terms Infection – occurs when the infectious agent begins to reproduce in the body – may result in a “case” – person with disease (symptoms) – Can be infected without disease! Typhoid Mary Pathogenicity – # with disease (symptoms) per # infected Virulence - # with severe illness or death per # with disease – Aka case fatality rate

12. More Key Terms Infectivity – capacity of the organism to cause infection in a susceptible individual Measure infectivity by: – Secondary attack rate – average number of other people one sick person infects # infected/# susceptible people exposed

13. Infectious Agents Prions – Protein based infectious particles Viruses – Genetic material (DNA, ssDNA, RNA…) inside a protein capsid – Many are vaccine preventable Bacteria – Prokaryotes – Some vaccine preventable Protozoa – Eukaryotes Fungus – Eukaryotes (molds and yeast) Worms – Parasitic multi-celled eukaryotes

14. Timeline of Infection Pre-Clinical Phase Infection occurs Disease can be detected through lab work Contagious Infected person may become contagious before or after symptoms begin Clinical Phase Symptoms develop Person recovers with or without immunity or dies

15. Major Infectious Diseases Worldwide HIV/AIDS – Virus Malaria – protozoa Tuberculosis (TB) – bacteria Measles – virus

16. Neglected Tropical Diseases (NTD) Diseases that have a significant impact on health and quality of life, but are generally not deadly http://www.who.int/neglected_diseases/en/ – ~23 minute video on the forgotten diseases http://whqlibdoc.who.int/publications/2010/9 789241564090_eng.pdf