Biological Definition Classification of Infection

Biological Definition Infection Method of Transmission The principles of best practice in infection control are based on extensive research and should be adopted in order to help prevent avoidable infections and to control existing ones. Infection control is especially important within healthcare settings, where the risk of infection to patients is greatly increased. An understanding of the infection process should lead to appropriate actions which help to protect patients, and healthcare workers themselves. Good infection control techniques adopted during patient care

Biological Definition Infection Method of Transmission
Biological Definition Infection Method of Transmission

The term cycle of infection is used to describe the processes leading to patients acquiring infection within healthcare settings. Knowledge of this cycle is essential in order to understand how infection can occur. All precautions and measures taken in order to prevent and control infection are based on the interruption of this cycle. It involves interaction between the host and the infecting microorganism. Based on their relationship to the host microorganism can be classified as saprophytes & parasites An infection can cause fever and other health problems, depending on where it occurs in the body. When the body’s immune system is strong,

Infection Definition Classification And Method of transmission

it can often fight the germs and cure an infection. Some cancer treatments can weaken the immune system, which may lead to infection.

The disease transmission cycle describes the six components required for the spread of an infectious organism to a susceptible host. The essential components in the cycle are the agent (disease-producing microorganism), reservoir (the place where the agent lives—humans, animals, plants, soil, air, water), mode of escape—how the agent exits the reservoir, mode of transmission, place of entry, and susceptible host. Each of these components must be present for the infection to be transmitted.

Saprophytes  The word came from greek papers that mean decayed & phyton means plant. They are free-living microbes that maintain dead or decaying organic matter. They are found in soil and water. Play an important role in the degradation of organic matter.

Infection Definition Classification And Method of transmission

Parasites They can either be pathogen greek pathos means suffering & gen means disease-producing or commensals come from Latin com means with & mensa means table i.e living together. They can establish themselves and multiply in hosts. The term infection & infectious disease is different. A place (lodgement) & multiplication of a parasite in or on the tissue of a host constitutes infection.

Infection Definition Classification And Method of transmission

Classification of infection

Health Care-Associated Infections of Public Health Concern Healthcare-associated infections can affect the cardiovascular, respiratory, gastrointestinal, and genitourinary tracts, central nervous systems, and bones and joints. HAIs may also affect skin, soft tissues, and muscles. HAIs of public health concern in many settings include:  Urinary tract infection (UTI), including catheter-associated urinary tract infection (CAUTI)  Bloodstream infection, including central line-associated bloodstream infection (CLABSI)  Surgical site infection (SSI)  Pneumonia, including ventilator-associated pneumonia (VAP)  Multidrug-resistant infections  Infectious Diarrhea and Clostridium difficile infections

1) Initial infection with a parasite in a host is called PRIMARY INFECTION.

2) Subsequent infections by the same parasite in the host are called REINFECTIONS.

3) When a new parasite sets up an infection in a host whose resistance is lowered by preexisting infection is called SECONDARY INFECTION.

4) When a patient already suffering from a disease a new infection is set up from another host or other source is called CROSS INFECTION.

5) Cross infections occurring in hospitals are called NOSOCOMIAL INFECTION.

6) Depending on whether the source of infection is within or outside the host’s own body, infection is classified as ENDOGENOUS or EXOGENOUS.

Apart from these basic terms mention above, some other infections are iatrogenic infection, inapparent infection, atypical infection, latent infection. The germs may be bacteria, viruses, yeast, fungi, or other microorganisms. Infections can begin anywhere in the body and may spread all through it

Infection Definition Classification And Method of transmission

Sources of infection

Healthcare-associated infection (HAI) is an infection that occurs in a patient as a result of care at a health care facility and was not present at the time of arrival at the facility. To be considered an HAI, the infection must begin on or after the third day of admission to the health care facility (the day of admission is Day 1) or on the day of or the day after discharge from the facility. The term “healthcare-associated infection” replaces the formerly used “nosocomial” or “hospital” infection because evidence has shown that these infections can affect patients in any setting where they receive health care.


The commonest source of infection in humans is they. It could be patients or carriers. The carriers can be healthy, convalescent. Depending on the duration carriers can be temporary & chronic. The temporary carrier lasts less than 6 months, while chronic last several year & sometimes rest of one’s life.


Many pathogens can infect both humans and animals. Therefore animals may act as a source of human infection. The infection in animals may be asymptomatic. They can serve to maintain the parasite in nature & act as a reservoir of human infections. They are called as RESERVOIR HOST.


Bloodsucking insects may transmit the pathogen to humans and cause a disease called ARTHROPOD –BRONE DISEASE.

Soil & water

Some pathogens can survive in the soil for very long periods spores of tetanus bacilli may remain viable in the soil for several decades & serve as a source of infection. Water may act as a source of infection due to contamination with pathogenic microbes such as cholera vibrio etc.


Again contaminated food may act as a source of infection. The presence of the pathogen in food may be due to external contamination (staphylococcus) or pre-existing infections such as meat or other animal products (Salmonella spp).

Infection Definition Classification And Method of transmission

Method of transmission of infection

  1. Contact:- Infection acquired by contact, which may be direct or indirect. The term contagious disease had been used for diseases transmitted by direct contact from infectious disease. Indirect contact may be through the agency of families, which are inanimate objects such as clothing, pencils that may be contaminated by the pathogen.
  2. Inhalation:- Respiratory infection such as influenza & tuberculosis is transmitted by inhalation of the pathogen such infection are shed by the patients into the environment during sneezing, coughing, or speaking in the form of a droplet.
  3. Ingestion:- Generally acquired by the ingestion of food or drink contaminated with the pathogen. It can be waterborne (cholera). Foodborne (food poisoning) or hand borne (dysentery).
  4. Inoculation:- Pathogen in some instances may be inoculated directly into the tissue of the host. Inoculation may be iatrogenic when unsterile syringes & surgical equipment are employed.
  5. Congenital:- Some pathogens can cross the placental barrier & infect the fetus. This is known as vertical transmission.
  6. Iatrogenic & laboratory infection:- Infection may sometimes be transmitted during the administration of infection. Modern methods of treatment such as transfusion, organ transplant surgery have increased the possibilities for such infection.

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Biological Definition Infection Method of Transmission

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4 thoughts on “Biological Definition Infection Method of Transmission Pdf Free 2021”

  1. Really good content in these Covid 19 days this is most important to know about the infection or there classes

    Biotech Era
    Radhika gupta

  2. It is very informative about to know the types of infections and also there classifcation,So that we can be aware about this. Good content about to know.
    Thanks biotech era and

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