2014-09-04
2095
An infection is the invasion of body tissues by disease-causing microorganisms, their multiplication and the reaction of body tissues to these microorganisms and the toxins that they produce. Infections are caused by microorganisms such as viruses, prions, bacteria, and viroids, though larger organisms like macroparasites and fungi can also infect. Hosts normally fight infections themselves via their immune system. Mammalian hosts (организм-носитель у млекопитающих) react to infections with an innate response, often involving inflammation, followed by an adaptive response. Pharmaceuticals can also help fight infections. The branch of medicine that focuses on infections and pathogens is infectious disease medicine.
Infections are classified in multiple ways. They are classified by the causative agent as well as by the constellation of symptoms and medical signs that are produced. An infection that produces symptoms is an apparent infection. An infection that is active, but does not produce noticeable symptoms, may be called inapparent, silent, or subclinical. An infection that is inactive or dormant (неактивная, латентная) is called a latent infection. A short-term infection is an acute infection. A long-term infection is a chronic infection.
II. Answer the questions to the text:
1) What is infection?
2) What can cause infections?
3) Via what does the human organism fight infections?
4) What branch of medicine is engaged in studying infections and pathogens?
5) How are infections classified?
6) What do we call a short-term infection?
7) What medical procedures can help to define a disease?
III. Match the words and their definitions:
| 1. inflammation 2. diagnosis 3. acute 4. virus 5. infection 6. toxin 7. latent 8. bacteria 9. tissue 10. symptom | a. a poisonous substance, especially one that is produced by bacteria b. the act or process of causing or getting a disease c. a tiny parasite living, growing and reproducing its kind inside a host cell that causes infectious diseases d. the simplest and smallest forms of life and are often a cause of disease e. a collection of cells that form the different parts of humans f. a condition in which a part of the body becomes red, sore and swollen because of infection g. a change in your body or mind that shows that you are not healthy h. existing, but not yet very noticeable, active or well developed i. very serious or severe j. the act of discovering or identifying the exact cause of an illness |
IV. Read about the difference between viral and bacterial infection and then speak about the symptoms that can help to distinguish them:
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Diagnosis of infections can be difficult as specific signs and symptoms are rare. If an infection is suspected, blood, urine and sputum cultures are usually the first step. Chest x-rays and stool analysis may also aid diagnosis. Spinal fluid can be tested to ensure that there is no brain infection. The symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue, loss of appetite, weight loss, fevers, night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes, coughing, or a runny nose. Bacterial and viral infections can both cause the same kinds of symptoms. It can be difficult to distinguish which is the cause of a specific infection. It's important to distinguish, because viral infections cannot be cured by antibiotics.
| Comparison of viral and bacterial infection | ||
| Characteristic | Viral infection | Bacterial infection |
| Typical symptoms | In general, viral infections are systemic. This means they involve many different parts of the body or more than one body system at the same time; i.e. a runny nose, sinus congestion, cough, body aches etc. They can be local at times as in viral conjunctivitis or "pink eye" and herpes. Only a few viral infections are painful, like herpes. The pain of viral infections is often described as itchy or burning. | The classic symptoms of a bacterial infection are localized redness, heat, swelling and pain. One of the hallmarks (отличительный знак) of a bacterial infection is local pain, pain that is in a specific part of the body. For example, if a cut occurs and is infected with bacteria, pain occurs at the site of the infection. Bacterial throat pain is often characterized by more pain on one side of the throat. An ear infection is more likely to be diagnosed as bacterial if the pain occurs in only one ear. A possibly infected cut that produces pus and milky-colored liquid is most likely infected. |
| Cause | Pathogenic viruses | Pathogenic bacteria |
V. Read the following text and translate it:
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The Source and Spread of Infection
There is a general chain of events that applies to infections. For infections to occur a given chain of events must occur. The chain of events involves several steps—which include the infectious agent, reservoir, entering a susceptible ( подходящий) host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop. Infection begins when an organism successfully colonizes by entering the body, growing and multiplying. Most humans are not easily infected. Those who are weak, sick, malnourished (получающие недостаточное питание), have cancer or are diabetic have increased susceptibility ( восприимчивость) to chronic or persistent infections. Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections. Entrance to the host generally occurs through the mucosa in orifices ( отверстия) like the oral cavity, nose, eyes, genitalia, anus, or open wounds. While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids.
Disease can arise if the host's protective immune mechanisms are compromised (под угрозой) and the organism inflicts damage on the host. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For infecting organisms to survive and repeat the infection cycle in other hosts, they (or their progeny) must leave an existing reservoir and cause infection elsewhere. Infection transmission can take place via many potential routes. Infectious organisms may be transmitted either by direct or indirect contact. Direct contact occurs when an individual comes into contact with the reservoir. This may mean touching infected bodily fluids or drinking contaminated water. Direct contact infections can also result from inhalation of infectious organisms found in aerosol particles emitted by sneezing or coughing. Indirect contact occurs when the microorganism is able to withstand the harsh environment outside the host for long periods of time and still remain infective when specific opportunity arises. Inanimate objects that are frequently contaminated include toys, furniture, door knobs, tissue wipes or personal care products from an infected individual. Consuming food products and fluid that have been contaminated by contact with an infecting organism is another case of disease transmission by indirect contact.
VI. Answer the questions to the text:
1) What chain of events can lead to infection?
2) When does infection begin?
3) What factors contribute to infection`s susceptibility?
4) Through what orifices do pathogenic microorganisms enter the human body?
5) How can infectious organisms be transmitted?
VII. Make dialogues between:
· a doctor and a patient with some infectious disease;
· an examiner and an examinee at the examination in infectious diseases
VIII. Match the given diseases with their descriptions:
mumps, diphtheria, gangrene, gastroenteritis, malaria, cholera, AIDS, tuberculosis.
1. A serious bacterial disease spread through infected food or water. The infected person suffers stomach cramps, diarrhea and dehydration. The disease is often fatal.
2. A viral disease spread mostly by sexual intercourse. It is also transmitted through infected blood and plasma transfusion, through using unsterilized needles for injections. It causes a breakdown of the body`s immune system.
3. A condition where tissues die and decay as a result of bacterial action because the blood supply has been lost through injury or disease of the artery.
4. A tropical, recurrent disease caused by a parasite Plasmodium which enters the body after a bite from the mosquito.
5. An infectious disease of children, with fever and swelling in the salivary glands, caused by a paramyxovirus.
6. Inflammation of the membrane lining the intestines and the stomach, caused by a viral infection, and resulting in diarrhea and vomiting.
7. A serious infectious disease of children. Its symptoms are fever and the formation of a fibrous growth like a membrane in the throat which restricts breathing.
8. An infectious disease, where infected lumps form in the tissue, its commonest form attacks the lungs, causing patients to lose weight, cough blood and have a fever.
IX. Read the following text and then be ready to speak on its content:
Microorganisms
Microorganisms were once regarded as being members of the plant kingdom, apart from protozoa ( простейшее) which were classified as animals. It became obvious that this arbitrary (произвольная) classification resulted in confusions, even absurdities. A virus infecting an animal cannot, by any criterion, be termed a plant. There became almost as many systems of classification as there were microbiologists.
In order to clarify the nature of microorganisms, we may distinguish between those, like fungi and some algae ( простейшие водоросли), which have a cell structure similar to higher organisms and those, like the bacteria and the blue-green algae, which have a comparatively simple cell structure. We will refer to the former as “higher protists ( простейшие)” and the latter as “lower protists”. The viruses cannot at present be adequately classified, so we shall place them in a group of their own.
