Microbio Ch 14 Q 34-68

38. Define symptoms

Changes in body function, such as pain and malaise (a vague feeling of body discomfort. These subjective changes are not apparent to an observer.

43. What is a noncommunicable disease? What are some examples?

Is not spread from one host to another.These diseases are caused by microorganisms that normally inhabit the body and only occasionally produce disease or by microorganisms that reside outside the body and produce disease only when introduced into the body. An example is tetanus: Clostridium tetani produces disease only when it is introduced into the body via abrasions or wounds.

54. What is a latent disease? Give an example.

Is one in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease; an example is shingles, one of the disease caused by varicella virus.

57. What is a local infection?

Is one in which the invading microorganisms are limited to a relatively small are of the body. Some examples of local infections are boils and abscesses.

51. What is an acute disease? Give an example

Is one that develops rapidly but only lasts a short time, and example is influenza.

63. What is a subclinical infection?

Is one that does not cause any noticeable illness. Poliovirus and hepatitis A virus, for example, can be carried by people who never develop the illness.

61. Define septicemia, bacteremia, toxemia and viremia

-Septicemia: also called blood poisoning, is a systemic infection arising from the multiplication of pathogens in the blood. Septicicemia is common example of sepsis. -The presence of bacteria in the blood is known as bacteremia. -Toxemia refers to the presence of toxins in the blood and viremia refers to the presence of viruses in blood.

52. What is a chronic disease? Give an example.

A chronic disease develops more slowly, and the body's reaction may be less serve, but the disease is likely to continue or reoccur for long periods. Infectious mononucleosis, TB, and hepatitis B fall into this category.

47. What is an endemic disease? Give an example

A disease constantly present is a population. I.e. the common cold.

53. What is a subacute disease? Give an example.

A disease that is intermediate between acute and chronic. i.e.subacute sclerosing pan encephalitis, rare brain disease characterized by diminished intellectual function and loss of nervous function.

65. What is a predisposing factor? Give examples of them.

A predisposing factor makes the body more susceptible to a disease and may alter the course of the disease.ender is some- times a predisposing factor; for example, females have a higher incidence of urinary tract infections than males, whereas males have higher rates of pneumonia and meningitis. Other aspects of genetic background may play a role as well. For example, sickle cell disease is a severe, life-threatening form of anemia that occurs when the genes for the disease are inherited from both parents. Individuals who carry only one sickle cell gene have a condi- tion called sickle cell trait and are normal unless specially tested. However, they are relatively resistant to the most serious form of malaria. The potential that individuals in a population might in- herit a life-threatening disease is more than counterbalanced by protection from malaria among carriers of the gene for sickle cell trait. Of course, in countries where malaria is not present, sickle cell trait is an entirely negative condition. Climate and weather seem to have some effect on the incidence of infectious diseases. In temperate regions, the incidence of respiratory diseases increases during the winter. This increase may be related to the fact that when people stay indoors, the closer contact with one other facilitates the spread of respiratory pathogens. Other predisposing factors include inadequate nutrition, fatigue, age, environment, habits, lifestyle, occupation, preexist- ing illness, chemotherapy, and emotional disturbances. It is often difficult to know the exact relative importance of the various predisposing factors.

62. What are primary and secondary infections? Why can the latter be more important?

A primary infection is an acute infection that cause the initial illness. A secondary infection is one caused by an opportunistic pathogen after the primary infection has weakened the body's defenses. Secondary infections of the skin are respiratory tract are common and are sometimes more dangerous that the primary infections.

49. What is a pandemic disease?

An epidemic disease that occurs worldwide.

41. What is a communicable disease? What are some examples?

Any disease that spreads from one host to another, either directly or indirectly. (i.e. chickenpox, measles, gentile herpes, typhoid fever, and TB are examples.

64. What is the sequence of events that occurs during infection and disease?

As you will learn shortly, for an infectious disease to occur, there must be a reservoir of infection as a source of patho- gens. Next, the pathogen must be transmitted to a susceptible host by direct contact, by indirect contact, or by vectors. Transmission is followed by invasion, in which the microorganism enters the host and multiplies. Following invasion, the microorganism in- jures the host through a process called pathogenesis (discussed further in the next chapter). The extent of injury depends on the degree to which host cells are damaged, either directly or by toxins. Despite the effects of all these factors, the occurrence of disease ultimately depends on the resistance of the host to the activities of the pathogen.

55. What influences the rate at which a disease spreads?

Determined in part by the immunity of the population.

42. What is a contagious disease? What are some examples?

Disease that are easily spread from one person to another. (i.e. chickenpox and measles)

40. Define disease

Diseases are often classified in terms of how they behave within a host and within a given population.

46. What is a sporadic disease? Give an example

Frequency of occurrence is another citron that is used in the classification of diseases. If a particular disease occurs only occasionally it is called a sporadic disease. i.e. typhoid fever

68. What are reservoirs of infection? Give examples.

Human reservoirs:The principal living reservoir of human disease is the human body itself. Many people harbor pathogens and transmit them di- rectly or indirectly to others. People with signs and symptoms of a disease may transmit the disease; in addition, some people can harbor pathogens and transmit them to others without exhibiting any signs of illness. These people, called carriers, are important living reservoirs of infection. Some carriers have inapparent in- fections for which no signs or symptoms are ever exhibited. Other people, such as those with latent diseases, carry a disease during its symptom-free stages—during the incubation period (before symptoms appear) or during the convalescent period (recovery). Typhoid Mary is an example of a carrier (see page 721). Human carriers play an important role in the spread of such diseases as AIDS, diphtheria, typhoid fever, hepatitis, gonorrhea, amebic dysentery, and streptococcal infections. Animal Reservoirs:Both wild and domestic animals are living reservoirs of micro- organisms that can cause human diseases. Diseases that occur primarily in wild and domestic animals and can be transmitted to humans are called zoonoses (zō-ō-noʹ sēz) (singular: zoonosis). Rabies (found in bats, skunks, foxes, dogs, and coyotes), and Lyme disease (found in field mice) are examples of zoonoses. Other rep- resentative zoonoses are presented in Table 14.2. About 150 zoonoses are known. The transmission of zoo- noses to humans can occur via one of many routes: by direct contact with infected animals; by direct contact with domestic pet waste (such as cleaning a litter box or bird cage); by con- tamination of food and water; by air from contaminated hides, fur, or feathers; by consuming infected animal products; or by insect vectors (insects that transmit pathogens). Nonliving Reservoirs:The two major nonliving reservoirs of infectious disease are soil and water. Soil harbors such pathogens as fungi, which cause mycoses such as ringworm and systemic infections; Clostridium botulinum, the bacterium that causes botulism; and C. tetani, the bacterium that causes tetanus. Because both species of clostridia are part of the normal intestinal microbiota of horses and cattle, the bacteria are found especially in soil where animal feces are used as fertilizer. Water that has been contaminated by the feces of humans and other animals is a reservoir for several pathogens, notably those responsible for gastrointestinal diseases. These include Vibrio cholerae, which causes cholera, and Salmonella typhi, which causes typhoid fever. Other nonliving reservoirs include foods that are improperly prepared or stored. They may be sources of diseases such as trichinellosis and salmonellosis.

48. What is an epidemic disease?

If many people in a given area acquire a certain disease in relatively short period. i.e. influenza

66. What are the five stages of a disease? Describe their characteristics.

Incubation Period The incubation period is the interval between the initial infection and the first appearance of any signs or symptoms. In some dis- eases, the incubation period is always the same; in others, it is quite variable. The time of incubation depends on the specific microorganism involved, its virulence (degree of pathogenicity), the number of infecting microorganisms, and the resistance of the host. (See Table 15.1, page 431, for the incubation periods of a number of microbial diseases.) Prodromal Period The prodromal period is a relatively short period that follows the period of incubation in some diseases. The prodromal period is characterized by early, mild symptoms of disease, such as general aches and malaise. Period of Illness During the period of illness, the disease is most severe. The per- son exhibits overt signs and symptoms of disease, such as fever, chills, muscle pain (myalgia), sensitivity to light (photophobia), sore throat (pharyngitis), lymph node enlargement (lymphade- nopathy), and gastrointestinal disturbances. During the period of illness, the number of white blood cells may increase or decrease. Generally, the patient's immune response and other defense mechanisms overcome the pathogen, and the period of illness ends. If the disease is not successfully overcome (or successfully treated), the patient dies during this period. Period of Decline During the period of decline, the signs and symptoms subside. The fever decreases, and the feeling of malaise diminishes. Dur- ing this phase, which may take from less than 24 hours to several days, the patient is vulnerable to secondary infections. Period of Convalescence During the period of convalescence, the person regains strength and the body returns to its prediseased state. Recovery has occurred. We all know that during the period of illness, people can serve as reservoirs of disease and can easily spread infections to other people. However, you should also know that people can spread infection during incubation and convalescence as well. This is especially true of diseases such as typhoid fever and chol- era, in which the convalescing person carries the pathogenic microorganism for months or even years.

50. Give examples an epidemic or a pandemic.

Influenza is an epidemic disease. An example of a pandemic disease is AIDS.

58. What is a systemic infection?

Microorganisms or their products are spread throughout the body by the blood or lymph. Measles is an example of a systemic infection.

67. What is needed for a disease to start and spread?

Reservoirs of Infection & Transmission of Disease

60. Define sepsis.

Sepsis is a toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection.

39. Define signs of disease. How do signs and symptoms differ?

Sings are objective changes the physician can observe and measure. Frequently evaluated signs include lesions (changes produced in tissue by disease), swelling, fever, and paralysis. A specific group of symptoms or signs may always accompany a particular disease; such a group is called a syndrome.

What are exceptions to Koch's Postulates?

The bacterium Treponema pallidum is known to cause syphilis, but virulent strains have never been cultured on artificial media. The causative agent of leprosy, Mycobacterium leprae, has also never been grown on artificial media. Moreover, many rickettsial and viral pathogens cannot be cultured on artificial media be- cause they multiply only within cells. The discovery of microorganisms that cannot grow on artificial media has necessitated some modifications of Koch's postulates and the use of alternative methods of culturing and detecting certain microbes.

45. What is the prevalence of a disease? What is the difference between the two?

The number of people in a population who develop a disease at a specified time, regardless of when it first appeared. Prevalence takes into account both old and new cases. It's an indicator of how seriously and how long a disease affects a population.

44. What is the incidence of a disease?

The number of people in a population who develop a disease during a particular time period.

What are Koch's Postulates?

The same pathogen must be present in every case of the disease. 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3. The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal. 4. The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.

59. What is a focal infection?

Very often, agents of a local infection enter a blood or lymphatic vessel and spread to other specific parts of the body, where they are confined to specific area of the body. Focal infections can arise from infections in areas such as the teeth, tonsils, or sinuses.

56. What is herd immunity?

When many immune people are present in a community.