Transmission of infection Flashcards
List the stages in the chain of infection.
Infectious agent Reservoir Portal of exit Means of trnsmission Portal of entry Susceptible host
Define virulence.
The ability of a microbe to cause disease.
Name 2 virulence factors.
Endotoxins: e.g. E.coli
Exotoxins: P.gingivalis
List possible reservoirs for infection.
Humans: Most pathogenic microbes that infect humans come from other humans.
Animals: Human pathogens can come from animals.
Environmental: Microbes that originate from the evironment.
Fomites: Contaminated objects/surfaces.
How easily recognised is infection in patients during the acute phase of infection?
Easily recognised
e.g. Flu and cold
How easily recognised is infection in patients during the podromal phase of infection?
Not easily recognised
e.g. Measles, mumps and chickenpox
How easily recognised is infection in healthy patients carrying pathogenic organisms?
Not easily recognised.
Those recovering from illness or those who are aymptomatic.
e.g. HIV and Hep B,C
Define incubation period.
The time between contamination and the development of symptoms. Patients can transmit the infection during this period.
What do infections with longer incubation periods allow?
Longer time periods for spreading the microbe.
Greater spread due to more human contact - dont know they are infectious yet due to lack of symptoms.
Define an asymptomatic carrier.
An infected person with no clinical evidence of disease (signs/symptom may have been evident early on)
Define colonisation. (as opossed to infection)
Presence of micro-organisms in/on a host with growth and multiplication but without any overt clinical expression at the time the microorganism is iscolated.
What is an endogenous reservoir?
An infection that is caused ny members of the normal flora. Becomes harmful due to gene expression shifts, become displaced to another body site or invade deeper tissues.
e.g. caries and perio
What is an exogenous reservoir?
Disease caused by microbes from external sources
e.g. influenza.
What are the 2 portal of exits?
Natural: Coughing/sneezing.
Artificial: Blood donation/ handpiece areosols.
How does COSHH classify human pathogens?
4 hazard groups based on;
Ability to cause infection
Severity of disease that may result
Vaccine and treatment availability
Risk of population spread.
