A set of training materials for professionals working in intervention epidemiology, public health microbiology and infection control and hospital hygiene.
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We refer to the source of infection as the origin from which a host acquires the infection, either endogenous (i.e. originating from a person's own commensal microbial flora) or exogenous (i.e. an individual, animal or object that in the external environment of the host). Usually the source can be identified as an individual, animal or object in a specific place, and at a specific time.
Thus, a person can be a source of infection; either for him/her self (endogenous) or to other people (directly through personal contact, or indirectly, e.g. by contaminating food or beverages).
In addition to people, also animals can be sources of infection
Objects may be sources of infection; food, water, air-conditioning systems, showers, medical instruments, recreational waters, door knobs, cotton handkerchiefs etc. Most man-made products that may be sources of infection are required to be produced while limiting the risk of contamination.
In most outbreak investigations, the principal objective is to identify the source of the infection. Interestingly enough this sometimes leads to semantic problems: an identified 'source' (e.g. a chocolate cake) is usually contaminated by some other source (e.g. the baker of the cake, or the eggs used). Tracing back such a 'chain of transmission' usually leads back to the reservoir. In a number of articles the concept of 'source' and 'reservoir' are used as synonyms, though strictly speaking they are not.
Inanimate sources of infection are sometimes referred to as 'vehicle of infection' (e.g. the chocolate cake) or 'fomites' (e.g. the cotton handkerchief). Inanimate sources (vehicles, fomites) are part of the indirect transmission route..
Source of infection should be distinguished from source of contamination (e.g. overflow of a septic tank, contaminating a water supply).
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Prattingerova Jana posted on 1/24/2012 8:41:52 AM:
I am a little bit confused. According Czech definition source of infections can be human, animal , or enviromental in origin ( only for legionela or some kind of mycobacterium).
Food , watrer etc are vehicles of infection.
Your example with a chocolate cake .... cake is vehicle, eggs used are vehicles and hen is source.
Who first defined the source of infection?
Arnold Bosman replied on 1/25/2012 1:21:28 AM:
Good question Jana, thank you. and I believe you are right. I am not completely sure if my interpretation is correct. This is how I understand it:
- Source is a broad concept that could cover people, animals, or inanimate objects.
- the term 'vehicle' is mostly used for specific type of sources in the specific context of indirect transmission routes: the transmission route can be vehicle borne, vector borne or airborne
So indeed, in the example, the chocolate cake etc are specific sources that can be called 'vehicles'.
This is how I interpret the information in the reference of David Heymann. Please let me know what you think about that.
Prattingerova Jana replied on 1/25/2012 10:13:04 PM:
I understand however I think it is a little bit complicated for those who are not experienced in epidemiology. It is a pity that there is not an international definition. I have read in The Lancet " ....such travel is an important source of infection". According to Czech definition it is a nonsence and e.g. student wouldn't pass his/her exam if he told this to the teacher.
Arnold Bosman replied on 1/25/2012 10:24:42 PM:
Thank you again. Perhaps this is a good reason that we could try to find an easier and more simple way of defining those concepts in the chapter online. For this purpose we have developed this FEMWIKI, to allow a larger group of experts provide input and exchange views.
If you would like, we would welcome some new texts that you could provide, in the chapter above, with the aim to reduce confusion.
This can be done by clicking on the 'edit' button on top of the chapter. Feel free to ask for some clarification if needed.
Prattingerova Jana replied on 1/27/2012 9:32:46 PM:
I will try to find the clearest one.Jana
Vladimir Prikazsky replied on 6/4/2015 11:21:01 AM:
I just had a little trigger for this discussion. If the agents can survive and multiply in water e.g. vibrio and other mentioned here above then water is a source. Otherwise it's a vehiculum. This has implications for investigation of the source.
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