Even the few drugs that are effective against specific viruses have limitations because viruses often produce different types of infection, have different host cells, or can cause serious side effects. General antibiotics are ineffective in preventing or curtailing viral infections. Unfortunately, most viral diseases can be treated only symptomatically, that is, by treating the symptom, not the infective cause. Viruses cause many clinically significant diseases in humans. For example, hepatitis C is known to have a latency period of 15 to 25 years. Some HIV patients have experienced prolonged periods of latency and have remained in good health for many years. Stress, infection with another virus, and exposure to ultraviolet light can reactivate the virus. A latent virus can be reactivated in the future and can produce more infective viral particles, followed by signs and symptoms of the disease. Some viruses establish a latent (dormant) state in host cells. The various forms of viral hepatitis and human immunodeficiency virus (HIV) are discussed in greater detail later in this chapter. Host cells may be human, animal, plant, or bacteria.Ī virus invades a host cell, replicates (produces copies of itself), and then destroys the host cell so the viruses are released into the body. Viruses can live and multiply only inside an appropriate host cell. New and increasingly destructive viruses are being discovered and have resulted in the creation of a special area within microbiology called virology (the study of viruses and their effects). Despite their tiny size, many viruses cause fatal diseases. Because of this incredible resistance, harmless spores are used to test the effectiveness of techniques used to sterilize dental instruments (see Chapter 8). They can survive extremes of heat and dryness and even the presence of disinfectants and radiation. Spores represent the most resistant form of life known. When conditions are again favorable, the bacteria become active and capable of causing disease. In the spore state, they cannot reproduce or cause disease. Tetanus is an example of a disease caused by a spore-forming bacillus.īacteria remain alive in the spore form, but are inactive. Under unfavorable conditions, some bacteria change into a highly resistant form called spores. Shapes of Bacteria and Diseases in Which They Occur Shape When viewed under a microscope, bacteria have three shapes: spherical, rod-shaped, and spiral ( Figure 5-1 and Table 5-1). Most bacterial infections are treated with antibiotics. An infection occurs when bacteria occurring naturally in one part of the body invade another part of the body and become harmful. They are beneficial and protect the human host by aiding in metabolism and preventing entrance of harmful bacteria. The skin, respiratory tract, and gastrointestinal tract are inhabited by a great variety of harmless bacteria, called normal flora. Humans host a variety of bacteria at all times. Pathogenic bacteria usually grow best at 98.6° F (37° C) in a moist, dark environment.Ī bacterial infection can be spread by many means of transmission. Most bacteria are capable of living independently under favorable environmental conditions. Bacteriaīacteria (singular bacterium) are a large group of one-celled microorganisms that vary in size, shape, and arrangement of cells. These microorganisms are so small that they can be seen only with a microscope. PathogensĪ pathogen is a microorganism that is capable of causing disease. You will learn how these diseases can be spread within the dental office and the steps you can take to protect yourself, other staff members, and patients from disease transmission in the dental office. In this chapter, you will learn about the organisms that cause infectious diseases and will learn to recognize the diseases that are of particular concern to dental professionals. The dental assistant is at risk of exposure to infectious diseases through occupational exposure. 1 Pronounce, define, and spell the Key Terms.Ģ Compare bacteria and viruses and give examples of each.ģ Discuss the causes of bacterial endocarditis.Ĥ Explain the differences between acute, chronic, latent, and opportunistic infections.ĥ Identify the modes of disease transmission in a dental office.Ħ Explain the concept of the chain of infection.ħ Name five ways in which disease transmission can occur in the dental setting.Ĩ Name the bloodborne diseases that are of major concern to dental healthcare professionals.ĩ Describe the portals of entry for disease transmission in a dental office.ġ0 Identify the diseases of concern to dental healthcare workers.ġ1 Explain the precautions necessary when treating a patient with active tuberculosis.
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