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caused by or capable of being communicated by infection.
infectious disease one due to organisms ranging in size from viruses to parasitic worms; it may be contagious in origin, result from nosocomial organisms, or be due to endogenous microflora from the nose and throat, skin, or bowel. See also communicable disease.

An emerging infectious disease is one that is endemic in a given population but that has begun increasing in frequency or developing resistance to drug therapy or other treatments.


1. A disease capable of being transmitted from person to person, with or without actual contact.
2. Synonym(s): infective
3. Denoting a disease due to the action of a microorganism.


/in·fec·tious/ (-fek´shus)
1. caused by or capable of being communicated by infection, as an infectious disease.
2. infective (1).


1. Capable of causing infection: an infectious microorganism.
2. Capable of being transmitted by infection: an infectious disease.
3. Capable of transmitting a disease; contagious: Is the patient still infectious?

in·fec′tious·ly adv.
in·fec′tious·ness n.


1 capable of causing an infection.
2 caused by an infection.


1. Referring to an infection.
2. Capable of spreading infection–eg, expulsion of infected aerosol by coughing or sneezing.


1. Capable of being transmitted by infection, with or without actual contact.
2. Caused by infection of the body by pathogenic organisms; not a synonym for contagious.
Synonym(s): contagion.
Synonym(s): infective.


capable of causing or transmitting infection


1. Disease capable of being transmitted from person to person, with or without actual contact.
2. Synonym(s): infective.


adj contagious; communicable; capable of causing infection.


caused by or capable of being communicated by infection.

infectious avian nephritis
caused by a picornavirus this disease of young chickens causes a transient unremarkable disease with lesions appearing in the kidney.
infectious bovine cervicovaginitis
thought to be due to a herpesvirus-4 infection, transmitted by coitus, causing sterility in a high percentage of cows and some bulls. Recorded only in South Africa. Called also epivag.
infectious bovine keratoconjunctivitis
the common infectious keratitis of cattle caused by Moraxella bovis with solar radiation, dust and face flies as contributing factors.. It occurs as outbreaks, characterized by ocular discharge, blepharospasm and pain. Underrunning of the conjunctiva leads to complications in a few cases. Called also pinkeye, blight, New Forest disease.
infectious bovine meningoencephalomyelitis
infectious bovine rhinotracheitis (IBR)
a highly infectious disease of cattle, particularly when crowded together as in feedlots, caused by bovine herpesvirus 1 and characterized by nasal discharge, rhinitis, tracheitis, conjunctivitis, fever and a short course unless complicated by other infections, particularly those leading to pneumonia. Less common forms of the disease include encephalitis in calves and a systemic infection in neonates, manifested by oral erosions and diarrhea. Infectious pustular vulvovaginitis is also caused by this virus. Called also rednose.
infectious bulbar paralysis
infectious caprine keratoconjunctivitis
contagious ophthalmia caused by Mycoplasma conjunctivae.
infectious coryza
see fowl coryza.
infectious equine anemia
see equine infectious anemia.
infectious equine bronchitis
see equine influenza.
infectious equine cough
see equine influenza.
infectious equine encephalomyelitis
see equine viral encephalomyelitis.
infectious hematopoietic necrosis of fish
important rhabdoviral infection of Onchorhyncus spp. especially steelhead (anadromous rainbow trout).
infectious hypodermal and hemopoietic necrosis
parvovirus infection causing high mortalities in juvenile Penaeus stylirostris and runt deformity syndrome in P. vanname.
infectious labial dermatitis
see contagious ecthyma.
infectious laryngotracheitis (ILT)
a highly infectious disease of birds of all ages caused by avian herpesvirus 1 and characterized by a very rapid spread of respiratory distress, the signs including gasping, respiratory gurgling and rattling, and death often from asphyxiation because of massive pseudomembrane formation in the trachea. The mortality rate may be as high as 70%.
infectious necrotic hepatitis
an acute toxemia of cattle, sheep and pigs caused by Clostridium novyi which elaborates a toxin in necrotic infarcts in the liver. These infarcts are caused usually by larvae of Fasciola hepatica. Many affected animals are found dead. Clinical findings include severe depression, hypothermia and muffling of heart sounds. Called also black disease.
infectious pancreatic necrosis of fish
a disease of salmonids caused by a group of related birnaviruses. It is characterized by hemorrhages and anemia, and spiral swimming and abdominal distention in fry.
infectious porcine dermatitis
see contagious porcine pyoderma.
infectious porcine polyarthritis
infectious pustular vulvovaginitis
see infectious pustular vulvovaginitis.
infectious salmon anemia
severe disease of Atlantic salmon, reported only, to date, from Norway; characterized by liver necrosis caused by an unidentified virus.
infectious serositis
a septicemic disease of young ducks caused by Riemerellaanatipestifer and characterized by torticollis, head tremor, loss of balance and a high mortality rate.
infectious sinusitis
a contagious disease of turkeys caused by Mycoplasma gallisepticum. The same infection also causes chronic respiratory disease of chickens. The disease in turkeys is characterized by swelling of the infraorbital sinuses, which are filled with thick exudate. The course is chronic and the death rate low but there is severe loss of condition and damage to the respiratory tract.
infectious stunting syndrome
caused by an enterolike virus this disease causes serious losses in the broiler industry; it is characterized by severe growth depression commencing at 1 week of age or earlier. Called also helicopter disease.
infectious synovitis
see infectious avian synovitis.

Patient discussion about infectious

Q. Is psoriasis infectious? Last week I and my friends from high-school went to the pool. One of my friend has psoriasis on his back, and when the lifeguard noticed it he asked him to leave the pool because he has skin disease that may spread to the other people swimming in the pool. We told him it is psoriasis and not some fungus, but he told us that psoriasis is also infectious. Is that true? Can psoriasis infect people who come in touch with people with psoriasis? Can I go swimming with him or should be more cautious?

A. It is right that psoriasis is not a contagious skin condition. But your friend should take care. However keeping skin humid is better for Psoriasis patients as I recently read these tips at

Q. Is leukemia contagious? A friend of mine got leukemia (blood cancer), can I get it from him if he bleeds and I touch the blood? Like HIV I mean.

A. No, you don't have to be afraid, no chance of that. Your friend will need you to pass this terrible illness. So I recommend learning a bit about leukemia so you understand it better and won't avoid your friend.
You can get information on those 2 sites:

Q. Is psoriasis contagious? My wife got psoriasis and I don’t want to get infected…

A. Psoriasis itself, as was written above, isn't contagious, i.e. if someone has psoriasis he or she can't transmit it to you. However, there is a form of psoriasis called psoriasis guttate that is associated with infection of the throat by a bacterium called streptococcus (which is contagious), so in some way it is contagious.

You may read more here:

More discussions about infectious
References in classic literature ?
The new point of view was infectious, and the next child did likewise, and then the next, till the whole three of them wailed loud.
He had been what was called a faithful husband; and when May had suddenly died--carried off by the infectious pneumonia through which she had nursed their youngest child--he had honestly mourned her.
Ferguson, still cold and impassible, talked of this, that, and the other; but he strove in vain to overcome this infectious gloominess.
The Vicar, notwithstanding medical assurance that the boy was no longer infectious, received him with suspicion; he thought it very inconsiderate of the doctor to suggest that his nephew's convalescence should be spent by the seaside, and consented to have him in the house only because there was nowhere else he could go.
He ordered dinners and suppers and obviously tried to appear cheerful, but his cheerfulness was not infectious as it used to be: on the contrary it evoked the compassion of those who knew and liked him.
Cadwallader was a large man, with full lips and a sweet smile; very plain and rough in his exterior, but with that solid imperturbable ease and good-humor which is infectious, and like great grassy hills in the sunshine, quiets even an irritated egoism, and makes it rather ashamed of itself.
Yet every time she said this she laughed again, and so infectious were her tones that I could only join her.
Every virulent form of infectious death stalked through the land.
Polly's laugh was so infectious that every one smiled and forgot to be shocked at her performance.
But firing is infectious - and see how rapidly he moves, with never a pause except as he whirls his horse about to take a new direction, never directly backward toward us, never directly forward toward his executioners.
s little white man-of-all-work coming into the room broke the spell, and I walked out of the house with a sort of dazed fear that delirium tremens might be infectious.
We bowed ourselves towards him, and answered, 'We were his humble servants; and accounted for great honour and singular humanity towards us that which was already done; but hoped well that the nature of the sickness of our men was not infectious.

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