Disease Transmission & Emerging/Re-emerging diseases Flashcards
Non-transmissible infectious diseases
Person cannot spread the disease to a new person (Tetanus)
Source/Reservoir in Direct transmission
Normally are the same thing
In indirect transmission, the source and reservoir are normally different
Droplets
Direct transmission
Airborne/aerosols
Indirect transmission
Transmission involving vectors
Indirect transmission
4 main groups of biological transmission
1- Propagative: multiplies, but no change/development (Bacteria)
2- Cyclopropagative: multiplies and changes/develops (protozoa)
3- Cyclodevelopmental: develops but doesn’t multiply (nematodes and trematodes)
4- Vertical: from mother to infant
Pathogen associated with surgical incisions
S. aureus
causes wound infections
Pathogen associated with urinary catheters
E. coli and other G-
causes UTIs
Pathogen associated with IV catheters
S. epidermidis
C. albicans
causes bacteremia and local infections
Pathogen associated with needlestick injuries
HBV, HCV, HIV
Causes hepatitis and AIDS
Pathogen associated with intubation
Pseudomonas aeruginosa
Klebsiella pneumoniae
Causes pneumonia
Pathogens transmitted by Aedes app.
Chikungunya
Dengue
Zika
Yellow fever
Disinfectant agents that can kill bacterial spores
H2O2
Formaldehyde
Chlorine
Glutaraldehyde
Only compounds that are both disinfectants and antiseptics in healthcare setting
Alcohols
H2O2
Sterilization by gamma rays/ionizing radiation
Disrupts DNA
Sterilization by microwaves/non-ionizing radiation
Disrupts cell membranes
Sterilization by H2O2 plasma
Free radicals interact w the cell membranes, enzymes or nucleic acids
Sterilization by ozone gas
Oxidation of cell membranes
Sterilization by autoclaving
Denatures and coagulates proteins
Sterilization by ethylene oxide gas
Alkylates amino acids, nucleic acids etc.
Autochthonous
native to the place where it is found endemically
Opportunistic pathogens
Require pre-existing host compromise
Exposure is accidental
Cannot infect and uncompromised host
True pathogens
Do not require a pre-existing compromise to infect.
Can infect healthy and imcl’d
Sometimes exposure is accidental
Virulence
Damage in a susceptible host due to a host-microbe interaction
Persistent infections
Not eliminated by the host immune system
Chronic: long duration, slow developing, shedding continues
Latent: genome maintained in host without replication. No shedding. (ex. TB)
Examples of Chronic persistent infections
Typhoid fever (S. typhi)
Leprosy
Syphillis
Examples of latent persistent infections
TB (M. tuberculosis)
3 classes of exotoxins:
Class I- membrane acting/bind to host cell surface
Class II- membrane damaging
Class III- intracellular
Pertussis toxin
ADP ribosylates G proteins– blocks inhibition of adenylate cyclase in susceptible cells.
Coagulase
converts fibrin to fibrinogen
Seen in S. aureus
Advantages of biofilm formation
1- Resistance to antimicrobial agents
2- Resist host immune response
3- Act as reservoir
Strategies for Fe acquisition by bacteria
1- Synthesis of surface receptors
2- Synthesis of siderophores
3- Reduction of Fe3+
Streptokinase
“invasins”
converts plasminogen to plasmin protease–> allows spread of infection by breaking down fibrin barrier.
Exs of emerging infectious disease:
Chikungunya
WNV
Exs of re-emerging infectious diseases
Measles
M. tuberculosis
Emerging diseases
- New/Never seen before
- old diseases occurring in a new place and/or a new population
- old diseases with new clinical presentations
- old disease that has become newly resistant to medications
CHIKV emergence
2013 emerged in the Caribbean
Outbreaks of fever and debilitating arthralgia
Autochthonous transmission
WNV outbreaks
1999- NE USA (NY, NJ, DE, MD)
2000- PA,VA, NC
2001- Midwest, and SE
2002- CA, rocky mountain states, TX
WNV emergence
widespread, multiple vectors (>30 different mosquitoes)
Birds are reservoir
Humans and Horses= dead-end hosts, who lack immunity.
Can infect >150 diff spp. of birds
No specificity of spp.
Re-emergence
Previously present and increasing again in incidence.
Due to:
- susceptible population
- changes in pathogen
Seen in vaccine-preventable diseases
Factors influencing disease emergence/re-emergence
1- Human demographics and behavior 2- Technology and industry 3- Economic development and land use 4- International travel and commerce 5- Microbial adaptation and change 6- Breakdown of public health infrastructure.
Ex of an emerging disease due to urbanisation
Dengue
Dengue
Flaviviridae
+ssRNA, icosahedral
Enveloped
Vector-borne daytime Aedes mosquito
