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Chain of infection; the chain of events that lead to infection. There is a general chain of events that applies to infections, sometimes called the chain of infection [14] or transmission chain. The chain of events involves several steps – which include the infectious agent, reservoir, entering a susceptible host, exit and transmission to new ...
The following outline is provided as an overview of and topical guide to concepts related to infectious diseases in humans.. Infection – transmission, entry/invasion after evading/overcoming defense, establishment, and replication of disease-causing microscopic organisms (pathogens) inside a host organism, and the reaction of host tissues to them and to the toxins they produce.
An infectious disease agent can be transmitted in two ways: as horizontal disease agent transmission from one individual to another in the same generation (peers in the same age group) [3] by either direct contact (licking, touching, biting), or indirect contact through air – cough or sneeze (vectors or fomites that allow the transmission of the agent causing the disease without physical ...
The host-pathogen interaction is defined as how microbes or viruses sustain themselves within host organisms on a molecular, cellular, organismal or population level. This term is most commonly used to refer to disease-causing microorganisms although they may not cause illness in all hosts. [1]
[39] [40] [41] The bacteria may start to cause disease when the host's immune system weakens, such as during a viral respiratory infection, which may lead to S. pyogenes superinfection. [40] [41] S. pyogenes infections are commonly associated with the release of one or more bacterial toxins.
While a few different bacterial infections can lead to meningitis, S. pneumoniae is one of the leading causes of this infection. Pneumococcal meningitis occurs when the bacteria goes from the blood to the central nervous system, which is made up of the brain and the spinal cord.
Other exceptions to Koch's postulates include evidence that some pathogens can cause several diseases, such as the varicella-zoster virus causing chickenpox and shingles. Conversely, diseases like meningitis can be caused by a variety of bacterial, viral, fungal, and parasitic pathogens. [11]
An opportunistic infection is a serious infection caused by pathogens (bacteria, fungi, parasites or viruses) that under normal conditions, such as in humans with uncompromised immune systems, would cause a mild infection or no infection at all. These opportunities can stem from a variety of sources, such as a weakened immune system (as can ...