infection, invasion of plant or animal tissues by microorganisms, i.e., bacteria bacteria [pl. of bacterium], microscopic unicellular prokaryotic organisms characterized by the lack of a membrane-bound nucleus and membrane-bound organelles. Once considered a part of the plant kingdom, bacteria were eventually placed in a separate kingdom, Monera.
..... Click the link for more information. , viruses virus, parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Viruses usually are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
..... Click the link for more information. , viroids viroid, microscopic infectious agent, much smaller than a virus, that infects higher plants such as potatoes, tomatoes, chrysanthemums, and cucumbers, causing stunted or distorted growth and sometimes death. It can be transmitted by pollen, seed, or farm implements.
..... Click the link for more information. , fungi Fungi , kingdom of heterotrophic single-celled, multinucleated, or multicellular organisms, including yeasts, molds, and mushrooms. The organisms live as parasites, symbionts, or saprobes (see saprophyte).
..... Click the link for more information. , rickettsias rickettsia , any of a group of very small microorganisms, many disease-causing, that live in vertebrates and are transmitted by bloodsucking parasitic arthropods such as fleas, lice (see louse), and ticks.
..... Click the link for more information. , and protozoans protozoan , informal term for the unicellular heterotrophs of the kingdom Protista. Protozoans comprise a large, diverse assortment of microscopic or near-microscopic organisms that live as single cells or in simple colonies and that show no differentiation into
..... Click the link for more information. . The invasion of body tissues by parasitic worms worm, common name for various unrelated invertebrate animals with soft, often long and slender bodies. Members of the phylum Platyhelminthes, or the flatworms, are the most primitive; they are generally small and flat-bodied and include the free-living planarians (of
..... Click the link for more information. and other higher organisms is commonly referred to as infestation.

Invading organisms such as bacteria produce toxins toxin, poison produced by living organisms. Toxins are classified as either exotoxins or endotoxins. Exotoxins are a diverse group of soluble proteins released into the surrounding tissue by living bacterial cells.
..... Click the link for more information. that damage host tissues and interfere with normal metabolism; some toxins are actually enzymes that, by breaking down host tissues, prevent the localization of infections. Other bacterial substances destroy the host's phagocytes. Viruses and retroviruses retrovirus, type of RNA virus that, unlike other RNA viruses, reproduces by transcribing itself into DNA. An enzyme called reverse transcriptase allows a retrovirus's RNA to act as the template for this RNA-to-DNA transcription.
..... Click the link for more information. are parasitic on host cells, causing cellular degeneration, as in rabies rabies or hydrophobia , acute viral infection of the central nervous system in dogs, foxes, raccoons, skunks, bats, and other animals, and in humans.
..... Click the link for more information. , poliomyelitis poliomyelitis , polio, or infantile paralysis, acute viral infection, mainly of children but also affecting older persons.
..... Click the link for more information. , and AIDS AIDS or acquired immunodeficiency syndrome, fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders.
..... Click the link for more information. , or cellular proliferation, as in warts wart, circumscribed outgrowth of the skin caused by a filterable virus that is readily transmitted. Warts may appear anywhere on the skin but are most common on the hands.
..... Click the link for more information. and cold sores. Some viruses have been associated with the development of certain cancers cancer, in medicine, common term for neoplasms, or tumors, that are malignant. Like benign tumors, malignant tumors do not respond to body mechanisms that limit cell growth.
..... Click the link for more information. . Substances produced by many invading organisms cause allergic sensitivity in the host; the immune response to virus infection has been implicated in some diseases (see allergy allergy, hypersensitive reaction of the body tissues of certain individuals to certain substances that, in similar amounts and circumstances, are innocuous to other persons. Allergens, or allergy-causing substances, can be airborne substances (e.g.
..... Click the link for more information. ).

Infections may be spread via respiratory droplets, direct contact, contaminated food, or vectors, such as insects. They can also be transmitted sexually (see sexually transmitted diseases sexually transmitted disease (STD) or venereal disease, term for infections acquired mainly through sexual contact. Five diseases were traditionally known as venereal diseases: gonorrhea, syphilis, and the less common granuloma inguinale,
..... Click the link for more information. ) and from mother to fetus. Immunity immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
..... Click the link for more information. is the term used to describe the capacity of the host to respond to infection. Drugs that help fight infections include antibiotics antibiotic, any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms. Types of Antibiotics

..... Click the link for more information. and antiviral drugs antiviral drug, any of several drugs used to treat viral infections. The drugs act by interfering with a virus's ability to enter a host cell and replicate itself with the host cell's DNA.
..... Click the link for more information. .

See also specific diseases, diseases of plants diseases of plants. Most plant diseases are caused by fungi, bacteria, and viruses. Although the term disease is usually used only for the destruction of live plants, the action of dry rot and the rotting of harvested crops in storage or transport is similar
..... Click the link for more information. .

Bibliography

See J. Waller, The Discovery of the Germ (2003).

infection

Invasion of the body by various agents—including bacteria, fungi (see fungus), protozoans, viruses, and worms—and its reaction to them or their toxins. Infections are called subclinical until they perceptibly affect health, when they become infectious diseases. Infection can be local (e.g., an abscess), confined to one body system (e.g., pneumonia in the lungs), or generalized (e.g., septicemia). Infectious agents can enter the body by inhalation, ingestion, sexual transmission, passage to a fetus during pregnancy or birth, wound contamination, or animal or insect bites. The body responds with an attack on the invader by leukocytes, production of antibodies or antitoxins, and often a rise in temperature. The antibodies may result in short-term or lifelong immunity. Despite significant progress in preventing and treating infectious diseases, they remain a major cause of illness and death, particularly in regions of poor sanitation, poor nutrition, and crowding.

infection

1. invasion of the body by pathogenic microorganisms

2. the resulting condition in the tissues

3. an infectious disease

infection [in′fek·shən]

(medicine)

Invasion of the body by a pathogenic organism, with or without disease manifestation.

Pathologic condition resulting from invasion of a pathogen.

Infection

A term considered by some to mean the entrance, growth, and multiplication of a microorganism (pathogen) in the body of a host, resulting in the establishment of a disease process. Others define infection as the presence of a microorganism in host tissues whether or not it evolves into detectable pathologic effects. The host may be a bacterium, plant, animal, or human being, and the infecting agent may be viral, rickettsial, bacterial, fungal, or protozoan.

A differentiation is made between infection and infestation. Infestation is the invasion of a host by higher organisms such as parasitic worms. See Epidemiology, Medical bacteriology, Medical mycology, Medical parasitology, Opportunistic infections, Pathogen, Virus

Infection

penetration of a pathogenic parasite into a human or animal organism and the state of being infected. The concept of infection is also applied to one-celled organisms (bacteriophages). On the other hand, there is a tendency to distinguish between the concept of infection and that of parasitism, including invasion.

Upon entering the body, the causative agent concentrates in certain organs and tissues. For example, in the course of evolution the itch mite adapted to parasitizing the epithelial layer of skin; the causative agent of typhus, Rickettsia prowazekii, the wall of arterioles and arterial capillaries; and the influenza virus, the mucous membrane of the upper respiratory tract. After the parasite enters the body, a complex interaction takes place between the parasite and host—an infectious process. The infectious process (dynamics of pathological changes) includes the causative agent’s adaptation to new conditions of existence and its reproduction, dissemination of the process, metastasis, and intoxication of the host. The infectious process and the functional disturbances in the host and its reflex reactions constitute the pathogenetic essence of infectious disease.

An infection is manifested as an acute or chronic form of the disease or carrier state. The development of a particular form depends, on the one hand, on the properties of the causative agent—its infectiousness, invasiveness, and capacity to form exotoxins and endotoxins—and on the number of parasites entering the organism. On the other hand, the condition of the organism and degree of susceptibility or predisposition to a given disease is a very important factor. The presence of certain causative agents in the organism does not provoke a pathological process unless some other conditions exist. Such causative agents are said to be conditionally pathogenic. They include the large group of causative agents of wound infections, many Escherichiaspecies, and herpesvirus. They may exist a long time without producing symptoms on the skin, on the mucous membranes, and in the intestine until an injury, chill, or other factor enables them to manifest their pathogenic properties.

An infected organism or carriers of the causative agents are the sources of infections. Every infectious disease has its own specific mechanism of transmission. In intestinal infections, such as dysentery or typhoid fever, the causative agent is eliminated from the body with feces or urine and in one way or another enters the mouth of a healthy individual. In infectious diseases of the respiratory tract, the causative agent is eliminated with drops of mucus during sneezing, coughing, or talking and penetrates into a healthy individual with inhaled air (the droplet mechanism of transmission). In typhus, malaria, bubonic plague, and some other diseases, the causative agent is trasmitted by blood-sucking insects—lice, mosquitoes, and fleas—parasitizing first a sick and then a healthy individual. The causative agents of scabies and fungal and venereal diseases are transmitted by direct contact with a diseased individual.

A knowledge of the mechanisms of transmission of infection is the basis of prevention of infectious diseases.

REFERENCES

Mechnikov, I. I. Newspriimchivost’ k infektsionnym bolezniam, 2nd ed. Moscow, 1947.
Gromashevskii, L. V. Obshchaia epidemiologiia, 4th ed. Moscow, 1965. Pages 29–45.

I. I. ELKIN

Mentioned in	?		References in periodicals archive	?		Encyclopedia browser	?		Full browser	?
No references found			``Within six months of his treatment, for the first time Rhys was able to play with pals without fear of terminal infection and finally return home. Gene therapy gives Rhys fresh hope by South Wales Echo (Cardiff, Wales) Eventually, damage to the nerves may be permanent, often leading to a person becoming disabled and needing constant care, and sufferers can become susceptible to potentially terminal infections such as TB and pneumonia. Health: Spot the difference. These women both have multiple ... by The Mirror (London, England) ``Within six months of his treatment, for the first time Rhys was able to play with pals without fear of terminal infection and finally return home. `Gene therapy' gives little Rhys fresh hope by South Wales Echo (Cardiff, Wales)			terminal air-traffic control terminal area terminal bar terminal based terminal block terminal board terminal box terminal brain death terminal bud terminal clearance capacity terminal control area terminal cutout pairs terminal disinfection terminal emulation terminal emulator terminal endocarditis terminal equipment terminal expense terminal figure terminal forecast terminal guidance terminal hair terminal illness terminal indecomposable future terminal indecomposable past terminal infection terminal junkie terminal leg terminal line terminal mode Terminal Moraine terminal nerve terminal network terminal node terminal operations Terminal Oriented Real Time Operating System Terminal Oriented Social Science terminal pair terminal pedestal terminal phase terminal pressure Terminal Productivity eXecutive terminal radar cab terminal reheat system terminal repeater terminal room terminal server Terminal Services terminal session terminal sinus terminal speed			Terminal Homing Munitions Projectile terminal hoof papilla terminal hoof papilla terminal hoof papilla Terminal Identification Terminal Ileal Transposition Procedure terminal ileitis terminal ileitis terminal ileitis terminal ileitis Terminal ileum Terminal illness Terminal illness Terminal illness Terminal illness Terminal illness terminal illness syndrome Terminal Imaging Radar terminal indecomposable future terminal indecomposable past Terminal Independent Mobility for Internet Protocol Terminal Indicate Assignment Terminal Indicate Capability Terminal Indicate Floor-Request Terminal Indicate Identity Terminal Indicate List Terminal Indicate Number Terminal Indicate Personal Identifier Terminal Indicate Secondary Terminal Indication Dropped terminal infection Terminal Information Terminal Initiated Channel Configuration Terminal Inner Medullary Collecting Duct Terminal Input Message Terminal Input Output Controller terminal insomnia Terminal Instrument Approach Procedure Terminal Instrument Procedure Terminal Instrument Procedures Terminal Integration Process Terminal Interface Message Processor Terminal Interface Processor Terminal Interface Program Terminal Interface System Terminal International Center Terminal Internet Gateway Terminal Internet Protocol Terminal Interworking Unit Terminal Inverted Repeat Terminal Island Container Transfer Facility Terminal Island Renewable Energy Terminal Island Treatment Plant Terminal Jaw Relation terminal jaw relation record terminal jaw relation record terminal jaw relation record terminal jaw relation record

Infection (redirected from terminal infection)

Bibliography

infection

REFERENCES

Infection
(redirected from terminal infection)