infectious

adj. causing infection; contagious, can be passed from one person to another; contaminating, polluting

An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply (usually at the expense of the host). The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss of an infected limb, and even death. The host's response to infection is inflammation. Colloquially, a pathogen is usually considered a microscopic organism though the definition is broader, including bacteria, parasites, fungi, viruses, prions, and viroids. A symbiosis between parasite and host, whereby the relationship is beneficial for the former but detrimental to the latter, is characterised as parasitism. The branch of medicine that focuses on infections and pathogens is infectious disease.
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Infectious /in·fec·tious/ 1. caused by or capable of being communicated by infection, as an infectious disease. 2. infective. in·fec·tious adj. 1. [more]Infectious - Community and Resources

Adjective
1. caused by infection or capable of causing infection; "viruses and other infective agents"; "a carrier remains infective without himself showing signs of the disease"
(synonym) infective
(similar) septic
2. easily spread; "fear is exceedlingly infectious; children catch it from their elders"- Bertrand Russell
(antonym) noninfectious
(similar) catching, communicable, contagious, contractable, transmissible, transmittable
3. of or relating to infection; "infectious hospital"; "infectious disease"
(pertainym) infection

(a.)
Having qualities that may infect; communicable or caused by infection; pestilential; epidemic; as, an infectious fever; infectious clothing; infectious air; infectious vices.
  

(a.)
Corrupting, or tending to corrupt or contaminate; vitiating; demoralizing.
  

(a.)
Contaminating with illegality; exposing to seizure and forfeiture.
  

(a.)
Capable of being easily diffused or spread; sympathetic; readily communicated; as, infectious mirth.