Human to Human Transmission of Infectious Diseases

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?

Factors that Affect Human Susceptibility to Infectious Diseases

Genetics Immunologic system function Environmental factors

Genetics

Sickle cell trait Evolutionary adaption to malaria Damaging as sickle cell disease

HIV Probably leprosy Others we do not understand

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

Breaker boys in coal mine - Lewis Hine

Immunosuppressive Drugs

A post 1960s phenomena Steroids

Asthma Arthritis Feel good docs

Chemotherapeutic agents Anti-rejection agents for transplants Impact on infection dynamics

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?

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

Transmission

Person to person Takes significant exposure Medicated by fomites

Animal hosts Milk Still a risk for raw milk

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

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

Legal Issues for TB

Detection Treatment Treatment failure/drug resistance