- •Infectious diseases.
- •Infectious pathogens ;
- •III. Form the nouns using the suffix(-tion), give their Russian equivalents:
- •IV.Make the words negative:
- •V.Complete this table:
- •VI.Read the text and answer the questions following it:
- •VII.Mix and match:
- •VIII.Make the sentences complete: Rickettsiae
- •IX.Read the text and answer the questions:
- •X. Give Russian equivalents to the following word - combinations:
- •XI. A) Note the difference in meaning of the given words
- •XII. A). Make the definitions of adjectives complete:
- •XVII. The words on the right can be used to form a noun that fits suitably in the blank space. Fill each blank in this way.
- •XVIII. Read the text and answer the questions after reading. Communicable disease epidemiology
- •XIX. Read about the chain of infection
- •XX. Say in one word:
- •XXI. Render from Russian into English : Инфекционные заболевания
- •XXII. Give the corresponding English names to the following diseases:
- •XXIV. Translate the definitions of these terms into English:
- •XXV. Render from Russian into English, use the suitable words from the active vocabulary:
- •XXVI. Translate from Russian into English:
- •XXVIII. Listen to the text “Infection” and retell it in Russian(appendix)
- •XXX. Check your knowledge of infectious diseases:
- •XXXI. Render from Russian into English, check your knowledge of the words dealing with the topic “Infectious diseases”:
- •Infectious diseases
- •I.Before reading the text look through the list of the following medical terms, be sure you know their meaning:
- •II. Answer the following questions:
- •III. Read the text «Treatment of tetanus» and make up a dialogue between a professor and a medical student discussing treatment options of a tetanus case. Treatment
- •Mild tetanus
- •Severe tetanus
- •IV. Listen the text “Tetanus” and retell it in Russian.
- •VI. Give Russian equivalents to the following word-combinations:
- •VII. Having obtained the information concerning tetanus fill in the gaps with proper words:
- •VIII. Use special medical terms from Ex.1:
- •IX. Render from Russian into English: Столбняк
- •Diagnosis
- •Prevention and Treatment
- •III.Fill in the gaps with the words in the list below:
- •IV.Make the sentences complete:
- •V.Read the text «Symptoms». Speak about the symptoms according to the plan:
- •Symptoms
- •VI.Listen the text «Leprosy». Retell the text using the following scheme:
- •Incubation
- •Involvement of
- •VII.Give Russian equivalents to these word-combination:
- •VIII.Render from Russian into English:
- •IX.Express your opinion of the psychologic and social problems that leprotic patients may suffer from.
- •X.Make up a dialogue between a specialist of the Center for Disease Control and Prevention and a journalist working in periodicals.
- •II. Read text fext "Pediculosis ". Pediculosis.
- •III. Make the sentence complete:
- •IV. Substitute English words for Russian ones: What do head lice look like?
- •V. Listen to the text "Pediculosis " and retell it in Russian:
- •VI. Fill in the gaps with prepositions in the box:
- •How is a head lice infestation diagnosed?
- •VII. Finish the sentences using obtained information:
- •VIII. Render from Russian into English:
- •Vocabulary:
- •IX. Say what you can:
- •Pediculosis.
XIX. Read about the chain of infection
The Chain of infection
Communicable diseases occur as a result of the interaction of the agent, the transmission process and the host. The control of such diseases may involve changing one or more of these components, all of which are influenced by the environment. These diseases can have a wide range of effects, varying from inapparent infection to severe illness and death.
The spectrum of illness from communicable disease:
INAPPARENT → MILD → SEVERE → DEATH
INFECTION │ DISEASE DISEASE │
No signs or │←Clinical illness with signs and symptoms→│
symptoms │ │
Knowledge of each factor in a chain of infection may be required before effective intervention can take place.
The infectious agent
A large number of microorganisms cause disease in humans. Infection is the entry and development or multiplication of an infectious agent in the host. Infection is not equivalent to disease. Some infections do not produce clinical disease. The specific characteristics of each agent are important in determining the nature of the infection, e.g., the types of toxin produced by the agent and its physical structure. The end result of infection is determined by a large number of factors involving all stages in the chain of infection. The pathogenicity of the agent, its ability to produce disease, is measured by the ratio of the number of persons developing clinical illness to the number exposed to infection. Virulence,
a measure of the severity of disease, can vary from very low to very high. Once a "virus has been attenuated in a laboratory and is of low virulence, it can be used for immunization, as with the poliomyelitis virus. Infectivity is the ability of the agent to invade and produce infection in the host. The infective dose of an agent is the amount required to cause infection in susceptible subjects.
The natural habitat of an infectious agent is called its reservoir, and may include humans, animals and environmental sources. The source of infection is the person or object from which the host acquires the agent. Knowledge of both the reservoir and the source is necessary if effective control measures are to be developed. An important source of infection may be a carrier, i.e. an infected person who shows no evidence of clinical disease. The duration of the carrier state varies between agents. Carriers can be asymptomatic throughout the course of infection or the carrier state may be limited to a particular phase of the disease.
Transmission
This, the second link in the chain of infection, is the spread of an infectious agent through the environment or to another person. Transmission may be direct or indirect.
Direct transmission is the immediate transfer of the infectious agent from an infected host or reservoir to an appropriate entry point through which human infection can take place. This may be by direct contact such as touching, kissing or sexual intercourse, or by the direct spread of droplets by sneezing or coughing.
Methods of transmission of an infectious agent
Direct transmission Indirect transmission
Touching Vehicle- borne (contaminated
Kissing water, towels, farm tools, etc.)
Sexual intercourse Vector-borne (insects, animals)
Other contact (e. g. childbirth, Airborne, long-distance(dust, droplets)
medical procedures, injection of Parenteral (injections with
drugs, breast-feeding) contaminated syringes)
Airborne, short-distance (via droplets,
coughing, sneezing) Transfusion (blood)
Transplacental
Blood transfusions and transplacental infection from mother to fetus may be other important means of transmission.
Indirect transmission may be vehicle-borne, vector-borne, or airborne. Vehicle-borne transmission occurs through contaminated materials such as food, clothes, bedding and cooking utensils. Vector-borne transmission occurs when the agent is carried by an insect or animal (the vector) to a susceptible host; the agent may or may not multiply in the vector. Long-distance airborne transmission occurs when there is dissemination of very small droplets to a suitable point of entry, usually the respiratory tract. Dust particles also facilitate airborne transmission, for example, of fungal spores.
The distinction between types of transmission is important when methods for control of communicable diseases are being selected. Direct transmission can be interrupted by appropriate handling of the source; indirect transmission requires different approaches, such as the provision of mosquito nets, adequate ventilation, cold storage for foods, the reduction of overcrowding, and a supply of sterile disposable syringes and needles.
Host
The host is the third link in the chain of infection and is defined as the person or animal that provides a suitable place for an infectious agent to grow and multiply under natural conditions. The points of entry to the host vary with the agent and include the skin, mucous membranes, and the respiratory and gastrointestinal tracts.
The reaction of the host to infection is extremely variable, being determined
by the interaction of host, agent and transmission factors. Infection may be unapparent or clinical, mild or severe. The incubation period the time between entry of the infectious agent and the appearance of the first sign or symptom of the disease varies from a few days (e.g. food-borne infection by salmonella) to years (AIDS).
An important determinant of the outcome of infection is the degree of natural or vaccine-induced resistance or immunity of the host. Immunity develops after an infection, after immunization, or through transmission of maternal antibodies via the placenta. Immunization is the protection of susceptible individuals from communicable disease by the administration of a modified living infectious agent (as for yellow fever), a suspension of killed organisms (as for pertussis), or an inactive agent (as for tetanus).
Environment
The environment plays a critical role in the development of communicable diseases. General sanitation, temperature, air pollution and water quality are among the factors that influence all stages in the chain of infection. In addition, socioeconomic factors, such as population density, overcrowding and poverty, are of great importance.
(Compiled from “Basic epidemiology”, WHO Geneva 1993) pp. 97-102)