SUSCEPTIBLE

adj. vulnerable, prone, liable to be affected by illness; emotionally sensitive, impressionable

In epidemiology a susceptible individual (sometimes known simply as a susceptible) is a member of a population who is at risk of becoming infected by a disease, if he or she is exposed to the infectious agent. Susceptibles have been exposed to neither the wild strain of the disease nor a vaccination against it, and thus have not developed immunity. Those individuals who have antibodies against an antigen associated with a particular infectious disease will not be susceptible, even if they did not produce the antibody themselves (for example, infants younger than six months who still have maternal antibodies passed through the placenta and from the colostrum, and adults who have had a recent injection of antibodies). However, these individuals soon return to the susceptible state as the antibodies are broken down.
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Adjective
1. (often followed by `of' or `to') yielding readily to or capable of; "susceptible to colds"; "susceptible of proof"
(antonym) unsusceptible, insusceptible
(similar) allergic, hypersensitive, hypersensitized, hypersensitised, sensitized, sensitised, supersensitive, supersensitized, supersensitised
(see-also) sensitive
(attribute) susceptibility, susceptibleness
2. easily impressed emotionally
(similar) impressionable, impressible

adj. touchy, sensitive, susceptible, susceptive

adj. susceptible, vulnerable, sensitive