Transcript Human to Human Transmission of Infectious Diseases

Human to Human Transmission of
Infectious Diseases
Basics of Disease Control
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Control the environment
Control the host
Control the vector
Why does this make diseases with human hosts
the most legally problematic?
Factors that Affect Human Susceptibility
to Infectious Diseases
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Genetics
Immunologic system function
Environmental factors
Genetics
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Sickle cell trait
 Evolutionary adaption to malaria
 Damaging as sickle cell disease
HIV
Probably leprosy
Others we do not understand
Environmental Factors
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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
Breaker boys in coal mine - Lewis Hine
Immunosuppressive Drugs
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A post 1960s phenomena
Steroids
 Asthma
 Arthritis
 Feel good docs
Chemotherapeutic agents
Anti-rejection agents for transplants
Impact on infection dynamics
Transmission Dynamics
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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?
Tuberculosis
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#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
Transmission
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Person to person
 Takes significant exposure
 Medicated by fomites
Animal hosts
 Milk
 Still a risk for raw milk
Detection
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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
Treatment of Active TB
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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
Legal Issues for TB
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Detection
Treatment
Treatment failure/drug resistance