12: Infectious Disease Flashcards
Infectious Disease Importance
- Significant cause of morbidity and mortality worldwide
- Associated with cancer (~10-15% cancers)
- Cause disease outbreaks in institutions
Epidemiologic Triangle
Used to explain etiology of infectious diseases. Three major factors in pathogenesis of disease: agent, host, and environment
Microbial Agents of Infectious Disease
- Bacteria
- Viruses and Rickettsia
- Mycoses
- Protozoa
- Helminths
- Arthropods
Bacteria
Once were leading killers, but now controlled by antibiotics. Remain significant causes of human illness. Emergence of antibiotic-resistant strains a growing concern.
Botulism, Cholera, Gonorrhea, Lyme Disease, Plague, Syphilis, Tetanus, TB, Typhoid Fever, Tularemia
BACTERIAL
Virus
Microorganism smaller than bacteria, which cannot grow or reproduce apart from living cell. Invades living cells and uses chemical machinery to replicate itself.
Rickettsial Agents
Gram negative bacteria that combines aspects of both bacteria and virus. Can reproduce only inside living cell. Organism can occur in cytoplasm of tissue cells or free in the gut of arthropods.
AIDS, Dengue Fever, Chickenpox, Hepatitis, Herpes, Measles, Mumps, Rabies, Rubella, West Nile, Ebola
VIRAL
Mycoses
Fungal Disease
- acts as a pathogen
- opportunistic mycoses (infect immunocompromised)
- Hospital-associated infections
- Community-acquired infections (Valley Fever)
Aspergillosis, Blastomycosis, Cryptococcosis, Histoplasmosis, Tinea Pedis
FUNGAL
Protozoa
Microscopic, one-cell organisms that can be free living or parasitic in nature. Able to multiply in humans, which contribute to their survival. Transmitted by fecal-oral route, via arthropod vector
Malaria, Amebiasis, Babesiosis, Leishamania, Cryptosporidiosis, Giardiasis
PROTOZOA
Leishmania Disease Presentation
- Cutaneous
- Mucocutaneous
- Visceral (Black Fever)
- No vaccines, use chemotherapies
Helminths
Large multicellular organism, either free living or parasitic. Typically found in tropical areas. Flatworms, Thorny-Headed Worms, or Roundworms.
Trichinellosis, Schistosomiasis
HELMINTHS
Alpers Syndrome, Creutzfeldt-Jakob Disease, Kuru, Fatal familial Insomnia, Transmissible Spongiform Encephalophathy
PRIONS
Arthropods
Act as insect vectors. Capable of transmitting bacteria, virus, and protozoa infections. Mosquitos, ticks, flies, mites
Infectivity
Capacity of agent to produce infection or disease. Measured by secondary attack rate. (new cases-initial cases)/(susceptible persons-initial cases) x 100
Pathogenicity
Capacity of agent to cause disease in infected host. Measured by proportion of individuals with clinically apparent disease. (ill+dead)/(infected) x 100
Virulence
Refers to severity of disease. Measured by proportion of total cases with overt infection divided by total number of infected cases. If fatal, use case fatality rate. (deaths)/(ill+infected) x 100
Toxigenicity
Capacity of agent to produce a toxin or poison.
Resistance
Ability of agent to survive adverse environmental conditions.