Lecture Outline - Chapter 16

16.1 Viral in Origin (p. 334, Fig. 16.2, Table 16.1)
	1.	Sexually transmitted diseases (STDs) are contagious diseases spread by pathogens transmitted from one person to the next through sexual contact. Viruses are obligate intracellular parasites that take over the host cell's machinery to produce more copies of themselves.
		a.	Viruses are made up of an outer proteinaceous capsid and an inner core of nucleic acid. Viruses contain DNA; retroviruses contain RNA.
		b.	Some viruses enter a period of latency, during which they are not actively producing symptoms in the host. Environmental factors and stress can trigger these viruses to again become active (Fig. 16.3).
		c.	Latent viruses can alter host cell chromosomes, triggering the development of cancer, as in the human papillomavirus causing cervical cancer.
	2.	Retroviruses are RNA viruses that contain reverse transcriptase, which produces DNA from viral RNA. The AIDS virus (HIV) is a retrovirus.
	3.	HIV Infection (p. 336, Fig. 16.4)
		a.	Prevalence of an HIV Infection and AIDS (p. 336)
			Most new HIV infections occur in heterosexuals--one every 15 seconds. As many as 20 million people worldwide may be infected, with especially high rates in Africa.
		b.	Symptoms of AIDS (p. 336)
			i.	HIV has a specificity for helper T cells. During the asymptomatic stage (category A), there are no symptoms, and people do not know they are infected. They are highly contagious at this stage.
			ii.	During the second stage, up to several years after infection, symptoms of pre-AIDS (category B) appear, and include swollen lymph nodes, severe fatigue, night sweats, and diarrhea. There may also be impaired mental functioning. 
			iii.	Full-blown AIDS (category C) is the final stage, when individuals become infected with opportunistic infections as their immune systems collapse. Most people die from an opportunistic infection, not AIDS itself.
		c.	Treatment for an HIV Infection (p. 337)
			Most treatments for HIV, such as AZT, interfere with the reverse transcriptase. Many investigators are working on an AIDS vaccine.
		d.	Transmission of HIV (p. 337)
			i.	HIV can be transmitted through sexual contact and from transferring body fluids from one person to the next (as in intravenous drug use with shared needles).
			ii.	Avoidance of HIV is the best choice because treatments are costly and limited, and there is no cure for AIDS.
	4.	Genital Warts (p. 337, Fig. 16.5)
		a.	Human papillomaviruses cause genital warts, which are sexually transmitted. Over 1 million people contract this virus annually.
		b.	Transmission and Symptoms (p. 337)
			Many carriers have no symptoms, or warts may be flat and scalelike. Newborns can become infected as they pass through the birth canal. Genital warts are associated with cervical cancer, which is on the rise in teens.
		c.	Treatment (p. 337)
			There is no cure for genital warts, but they can be treated with laser or cryosurgery. Use of a condom with nonoxynol-9 is recommended to prevent the spread of genital warts.
	5.	Herpes Infections (p. 338)
		a.	Herpes viruses are responsible for a variety of human illnesses, from chicken pox to shingles to cold sores and mononucleosis.
		b.	Cold Sores and Fever Blisters (p. 338)
			Herpes simplex type 1 is responsible for cold sores, and herpes simplex type 2 causes genital herpes. Type 1 may be transmitted to the genitals through active cold sores.
		c.	Genital Herpes (p. 338, Fig. 16.6)
			i.	At least 1 million new cases of genital herpes appear each year, many of which have few symptoms. Fever blisters may appear on the genitals and leave painful ulcers. They may be accompanied by fever and pain on urination.
			ii.	After the initial outbreak heals, the virus is latent until stress or environmental influences cause its recurrence.
			iii.	Infection of newborns through active lesions can lead to blindness, brain damage, or death.
		d.	Transmission (p. 338)
			Herpes lesions shed active viruses, so all contact with lesions should be avoided.
		e.	Treatment (p. 338)
			There is no cure for genital herpes, but some drugs disrupt viral reproduction.
			HEALTH FOCUS: STDs and Medical Treatment (p. 339)
			Medical treatment of STDs is increasingly difficult, due to the rapid evolution of resistant strains of pathogens. Prevention is the best way to manage STDs.
	6.	Hepatitis Infections (p. 339)
		a.	Hepatitis A is carried in sewage-contaminated drinking water and can also be transmitted through sexual contact. Hepatitis B is highly contagious and is usually spread by sexual contact. Hepatitis C is the post-transfusion form of hepatitis, which can lead to liver cancer and death. Other types of hepatitis are also under investigation.
		b.	Hepatitis B (p. 339)
			i.	Hepatitis B is spread in the same manner as HIV, and most people with HIV have this. About half of those infected experience flulike symptoms and jaundice. Some have an acute infection from which they recover; others get the chronic form that can lead to liver failure.
			ii.	There is no treatment for hepatitis B, although a vaccine is now available.
16.2 Bacterial in Origin (p. 340; Figs. 16.7, 16.8; Table 16.2)
	1.	Most bacteria are free-living organisms that reproduce asexually. Many perform useful services in the digestive tract and are a part of the normal microbial flora. Bacterial diseases can be passed directly from one person to the next and can be controlled by hand washing and "safe sex" methods. Bacterial diseases respond to antibiotic therapy.
	2.	Chlamydia (p. 342, Fig. 16.9)
		a.	Chlamydia is caused by a tiny bacterium that enters cells by endocytosis. New chlamydial infections are more frequent than any other STD because many cases go undetected.
		b.	Symptoms (p. 342, Fig. 16.10)
			i.	Usually, symptoms are mild, such as a burning sensation upon urination and a discharge in men. Women have symptoms similar to urinary tract infections and can be treated with the wrong antibiotics.
			ii.	Chlamydial infection can lead to pelvic inflammatory disease (PID) in women, a painful condition that can result in sterility.
		c.	Diagnosis and Treatment (p. 342) 
			New tests are available for diagnosis of chlamydia, and it can be cured with tetracycline.
	3.	Gonorrhea (p. 343, Figs. 16.11, 16.12)
		a.	Gonorrhea is caused by a bacterium, and its incidence has declined.
		b.	Symptoms (p. 343)
			i.	Symptoms in males are more obvious; usually, painful urination is the first clue.
			ii.	Most women are asymptomatic, which can lead to PID.
		c.	Transmission and Treatment (p. 343)
			Gonorrhea can be transmitted through sexual contact. Blood tests are being developed, but discharge needs to be examined to identify this bacterium at present. Antibiotics can clear up an infection, although resistant strains are surfacing.
	4.	Syphilis (p. 344, Fig. 16.13)
		a.	Syphilis is caused by the bacterium Treponema palladium and is on the decline. This disease has three stages, the first of which involves a hard chancre at the site of infection. The second stage occurs after a latent period and involves a systemic rash. Another latent period follows, and in some people, a third stage is seen, during which the disease progresses throughout the body and weakens arterial walls. Death eventually follows.
		b.	Diagnosis and Treatment (p. 344)
			Blood tests and microscopic examination of fluids from lesions can confirm the presence of this pathogen. Penicillin can cure syphilis in any stage.
16.3 Other Sexually Transmitted Diseases (p. 345)
	1.	A protozoan causes a form of vaginitis in women.
	2.	Vaginitis (p. 345, Fig. 16.14)
		The yeast Candida albicans, usually present in the vagina, can sometimes increase beyond normal, producing vaginitis.
	3.	Pubic Lice (Crabs) (p. 345, Fig. 16.15)
		The parasitic crab louse causes pubic lice. Pubic lice can be contracted by direct contact with an infected person or by contact with his or her clothing. Medications can kill the lice, and all clothing and bedding should be washed in hot water.