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