Communicable Diseases

1. Communicable Diseases

2. Communicable Diseases - Poverty • Lack of access to clean water and sanitation • Lack of access to health care • Limited knowledge of appropriate health behaviors

3. 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.

4. 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.

5. HIV/AIDS • 40 million people infected (text) • 2005 – 2.3 million died from AIDS • 2005 – 4.3 million new cases UNAIDS 2010 Report • 2009 – 1.8 million died • 2009 – 2.6 million newly infected

6. TB • ~1/3 of world is infected with TB • 9 million in the world with active TB • An estimated 1.7 million people died from TB in 2009 (WHO) • HIV + individuals who also have TB are much more likely to develop active TB and die

7. Malaria • In 2010: • 216 million cases of malaria • an estimated 655,000 malaria related deaths, mostly among African children. (WHO) • Malaria is preventable and curable.

8. 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

9. 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

10. 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

11. 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)

12. 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

13. 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

14. 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 • HIV/AIDS

15. 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

16. Key Terms • Infection • Pathogenicity • Virulence • Virulence Factors • Infectivity

17. Terms • Pathogenicity – # with disease (symptoms) per # infected • ability to cause disease is called pathogenicity • Virulence- # with severe illness or death per # with disease • Measure of the degree of pathogenicity • Sometimes expressed as a case fatality rate • Often consider lethal dose response….how many organisms needed to cause death (P. Milligan)

18. Terms • Virulence factors - properties (i.e., gene products) that enable a microorganism to establish itself on or within a host and enhance its potential to cause disease. • Virulence Factors database

19. Virulence factors include: • bacterial toxins • cell surface proteins that mediate bacterial attachment • cell surface carbohydrates and proteins that protect a bacterium • hydrolytic enzymes that may contribute to the pathogenicity of the bacterium.

20. 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

21. 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

22. Timeline of Infection

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

24. 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 • Alternate video NTD in Africa ~7 minutes • http://whqlibdoc.who.int/publications/2010/9789241564090_eng.pdf

25. Malaria life cycle in mosquito • Malaria in human