1. Unit 4 – Public Health Infectious Diseases
Chapter 9 – The “Conquest” of Infectious Diseases

2. Infectious Diseases – Major Killers in Past
Bubonic plague – “Black Death”
Tuberculosis
Smallpox
Cholera
Typhoid
Typhus
Yellow Fever
Diphtheria
Measles
Influenza

3. Infectious Diseases Were “Conquered” by 1960s
Immunization
Antibiotics

4. Infectious Agents
Bacteria – tuberculosis, cholera, typhoid, tetanus, diphtheria, dysentery, syphilis, streptococci, staphylococci
Viruses – smallpox, poliomyelitis, hepatitis, measles, rabies, AIDS, yellow fever
Parasites – malaria, cryptosporidiosis, giardiasis, roundworms, tapeworms, hookworms, pinworms

5. Chain of Infection Pathogen (infectious agent) Reservoir
Means of transmission
Susceptible host
Interrupt chain of infection at any link

6. Means of Transmission Aerosol
Touching contaminated object and putting hands to mouth, nose, or eyes
Contaminated water or food: fecal-oral route
Vectors
Sexual contact

7. Interrupting Chain of Infection
Kill pathogen with antibiotics
Eliminate reservoir
Prevent transmission
Wash hands
Quarantine
Condom
Increase resistance of host by immunization

8. Public Health Measures
Epidemiologic surveillance
Contact tracing
Immunization and treatment of identified patients to prevent further spread
Quarantine if necessary

9. Examples SARS – controlled by classic public health measures Rabies
Surveillance of wildlife
Immunization of dogs
Post-exposure prophylaxis

10. Eradication Possible if no non-human reservoir and a vaccine exists
Smallpox eradicated in 1977
Polio eradicated from Western Hemisphere
Now only in a few countries
Religious opposition in some countries
Measles is next target
Now no longer endemic in U.S.

11. Fear of Vaccines Rumors of vaccines causing autism, SIDS
Side effects do exist for some vaccines
Some parents refuse to accept risks
Herd immunity -- lost if many people do not get vaccinated
Pharmaceutical companies reluctant to develop vaccines
Low profits
Risk of lawsuits

12. Unit 4 – Public Health Infectious Diseases
Chapter 10 – The Resurgence of Infectious Diseases

13. HIV/AIDS First recognized in U.S. in 1981. Now a world-wide killer
Caused by a retrovirus
Attacks the immune system
Screening test recognizes antibodies
Can measure viruses in the blood
Now many drugs are available, but no cure

14. HIV/AIDS Transmission
Sexual contact
Homosexual – most common in U.S.
Heterosexual – most common around the world
Sharing needles
Intravenous drug use
Medical use of unsterile needles
Mother to infant
Prenatal or during birth
Breast feeding
Blood transfusions
No longer in U.S.

15. Where Did HIV Come From? Probably originated in Africa
Cross-species transmission from monkeys or apes
Spread in human populations due to disruption of traditional lifestyles
Spread to Western countries due to changing patterns of sexual behavior and international travel

16. Other Emerging Viruses
Ebola
Monkey pox
Hantavirus
Other hemorrhagic fevers
West Nile virus
SARS

17. Factors that Lead to Emergence of New Infectious
Human activities that cause ecological damage and close contact with wildlife
Modern agricultural practices
International travel
International distribution of food and exotic animals
Breakdown of social restraints on sexual behavior and intravenous drug use

18. Influenza Virus is constantly mutating
Vaccine must be changed frequently
New, lethal strains appear periodically
Epidemic of killed 20 million to 40 million worldwide
Concern about bird flu in Asia

19. New Bacterial Threats Legionnaire’s Disease Lyme Disease
Streptococcus A
E. coli O157:H7 in food
Antibiotic resistance
From improper medical use
Use in agriculture

20. Tuberculosis
Leading cause of infectious–disease death worldwide; one third of world population is infected
There was a resurgence in the U.S. in early 1990s
Much higher risk for people with HIV
Transmitted by aerosol
50% fatality rate for untreated TB

21. Tuberculosis, ctd
Antibiotics are effective, but must be taken for several months
Improper use of antibiotics leads to resistance, including multidrug resistance, when mortality rate can be 50%
Directly observed therapy works – best approach to preventing antibiotic resistance

22. Prions Creutzfeld-Jacob disease (CJD) – sporadic, in older people
Bovine spongiform encephalopathy (BSE) or “mad cow disease” in Britain
New variant CJD in Britain in younger people, thought to be caused by eating infected beef
Regulations have been tightened on animal feed

23. Public Health Response to Emerging Infections
Global surveillance
Improve public health capacity
Veterinary surveillance
Reduce inappropriate use of antibiotics
Need for new vaccines
Need for new antimicrobial drugs
Control of vector-borne and animal-borne diseases

24. Threat of Bioterrorism
Approach to bioterrorism is the same as that for natural disease outbreaks
Will probably first be recognized by surveillance
Best defended against by same methods as natural outbreaks