Human to Human Transmission of Infectious Diseases

1
Human to Human Transmission of Infectious Diseases
2
Basics of Disease Control

• Control the environment
• Control the host
• Control the vector
• Why does this make diseases with human hosts the
  most legally problematic?

3
Factors that Affect Human Susceptibility to
Infectious Diseases

• Genetics
• Immunologic system function
• Environmental factors

4
Genetics

• Sickle cell trait
• Evolutionary adaption to malaria
• Damaging as sickle cell disease
• HIV
• Probably leprosy
• Others we do not understand

5
Environmental Factors

• Factors that affect immunologic function
• Nutritional status
• Stress
• What does this tell us about developing countries
  and refugee camps?
• Factors that increase exposure/cause stress
• Crowded housing
• Poor sanitation
• Poor working conditions

6
Breaker boys in coal mine - Lewis Hine
7
Immunosuppressive Drugs

• A post 1960s phenomena
• Steroids
• Asthma
• Arthritis
• Feel good docs
• Chemotherapeutic agents
• Anti-rejection agents for transplants
• Impact on infection dynamics

8
Transmission Dynamics

• How hard is it to catch the disease? (Contact
  effectiveness)
• Measles
• Leprosy (Hanson's Disease)
• How susceptible is the population?
• Immunity?
• Environmental factors?
• How many people are infectious carriers?
• How well do the carriers mix with the general
  population?
• Are there high risk subgroups?

9
Tuberculosis

• 1 Killer, probably for all time
• Mycobacterium tuberculosis
• Related to leprosy
• Very hard to kill
• Can lay dormant for decades
• Can affect any organ system
• Dangerous when it is pulmonary - you cough up the
  bugs and spread them

10
Transmission

• Person to person
• Takes significant exposure
• Medicated by fomites
• Animal hosts
• Milk
• Still a risk for raw milk

11
Detection

• TB skin testing
• Looking for antibody reaction
• Not so good in immunosuppressed people
• Conversion
• You are infected
• You may not have actively growing bugs
• Confirmation
• HIV test
• X-ray
• Treatment - 1 year of isoniazid

12
Treatment of Active TB

• Active - pulmonary infection that can spread
  infectious material
• Treatment
• Takes time to make the patient non-infectious
• Much longer or never for drug resistant
• Long course for cure
• Incomplete treatment
• drug resistant
• worst case - pan drug resistance

13
Legal Issues for TB

• Detection
• Treatment
• Treatment failure/drug resistance