4. 10/19/2023
• Pathogens (infectious agent)
• Reservoir
• Means of transmission
• Susceptible host
• Interrupt chain of infection at any link
Chain of Infection
4
5. 10/19/2023
• Aerosol
• Touching contaminated object and putting hands to
mouth, nose, or eyes
• Contaminated water or food: fecal-oral route
• Vectors
• Sexual contact
Means of Transmission
5
6. 10/19/2023
• Kill pathogen with antibiotics
• Eliminate reservoir
• Prevent transmission
o Wash hands
o Quarantine
o Condom
• Increase resistance of host by immunization
Interrupting Chain of Infection
6
7. 10/19/2023
• Epidemiologic surveillance
• Contact tracing
• Immunization and treatment of identified patients to prevent further
spread
• Quarantine if necessary
Examples
• SARS- controlled by classic public health measures
• Rabies
o Surveillance of wildlife
o Immunization of dogs
o Post-exposure prophylaxis
Public Health Measures
7
8. 10/19/2023
• Possible if no non-human reservoir and a vaccine
exists
• Smallpox eradicated in 1977
• Polio eradicated from Western Hemisphere
o Now only in a few countries
o Religious opposition in some countries
• Measles is next target ( Now no longer endemic in
U.S.)
Eradication
8
9. 10/19/2023
• 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
o Low profits
o Risk of lawsuits
Fear of Vaccines
9
10. 10/19/2023
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
The Resurgence of Infectious Diseases
10
11. 10/19/2023
• Sexual contact
o Homosexual- most common in U.S.
o Heterosexual- most common around the world
• Sharing needles
o Intravenous drug use
o Medical use of unsterile needles
• Mother to infant
o Prenatal or during birth
o Breast feeding
• Blood transfusions
o No longer in U.S.
HIV/AIDS Transmission
11
12. 10/19/2023
• Probable 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
Where Did HIV Come from?
12
13. 10/19/2023
• Ebola
• Monkey pox
• Hantavirus
• Other hemorrhagic fevers
• West Nile Virus
• SARS
Other Emerging Viruses
13
14. 10/19/2023
• 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
Factors that Lead to Emergence of New
Infectious
14
15. 10/19/2023
• Virus is constantly mutating
• Vaccine must be changed frequently
• New, lethal strains appear periodically
• Epidemic of 1918-1919 killed 20 million to 40
million worldwide
• Concern about bird flu in Asia
Influenza
15
16. 10/19/2023
• Legionnaire’s Disease
• Lyme Disease
• Streptococcus A
• E.coli O157:H7 in food
• Antibiotic resistance
o From improper medical care use
o Use in agriculture
New Bacterial Threats
16
17. 10/19/2023
• Leading cause of infectious-disease death
worldwide; one third of world population is infected
• There was a resurgence in U.S. in early 1990s
• Much higher from people with HIV
• Transmitted by aerosol
• 50 % fatality rate from untreated TB
Tuberculosis
17
18. 10/19/2023
• 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
Tuberculosis, CTD
18
19. 10/19/2023
• 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
Prions
19
20. 10/19/2023
• 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
Public Health Response to Emerging
Infections
20
21. 10/19/2023
• 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
Threats of Bioterrorism
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