Lecture Notes, Biology 203, Human Sexuality and Reproduction

Sexually Transmitted Diseases, Part 1

  1. Introduction
    1. Diseases, organization
      1. More serious, life threatening: AIDS, syphilis
      2. Serious consequences: gonorrhea, chlamydia, herpes, genital warts
      3. Less serious: trichomonas, candida, gardnerella
    2. Characteristics of diseases: cause, how you get it, symptoms and incubation period, complications, long-term risk, diagnosis, treatment, vaccine, epidemiology, misc. issues
    3. Center for Disease Control, Atlanta: records case frequency, distribution for reportable diseases, traces contacts, epidemiology
    4. Worldwide STD cases (graph)
      1. Most common: Trichomonas
      2. Middle group: chlamydia, gonorrhea, genital warts, genital herpes
      3. Least common: AIDS
    5. Responsibility/ethics: the person who has the symptoms of an STD has the responsibility to tell their sexual partners about an STD
  2. Acquired Immune Deficiency Syndrome (AIDS)
    1. Incidence/mortality
      1. 1985: 1200 cases/450 dead
      2. 1997: 600,000 cases/380,000 dead
      3. 6/2001: 793,000 cases/458,000 dead (649,000 male, 135,000 female, 9000 children)
      4. 5th leading cause of death in U.S. for ages 25-44
      5. In top 10, Illinois 6th highest state, Chicago 6th highest city (St. Louis and MO not in top 10)
    2. Infectious agent: human immunodeficiency virus (HIV)
      1. Viruses can't reproduce by themselves, but require a host cell to supply the energy and other materials necessary
      2. A virus binds to a specific host cell by attaching to receptor molecules on the host cell surface.
      3. A host cell with no receptors for a particular virus can't be infected by that virus.
      4. The receptor on human cells that binds HIV is a molecule called CD4, found on immune system cells, as well as on cells in the brain and intestinal lining
      5. Cells of the immune system (T-helper lymphocytes) that are CD4-positive are ones that help make a protective response to infectious agents (such as bacteria, viruses, fungi, protozoa)
      6. HIV are made of RNA (containing genetic information) surrounded by viral coat proteins and enclosed in a viral envelope (membrane material acquired when the virus left the preceding host cell)
      7. Viral proteins in the envelope are recognized by the human immune system, but the immune response is not protective.
      8. Another viral protein, fusin, helps the virus enter the host cell
      9. HIV binds to CD4-positive lymphocytes and eventually destroys them, increasing the infected person's susceptibility to infectious diseases
      10. Many more people are infected with HIV than have HIV disease or AIDS (see diagram)
      11. The largest number of people are infected with the virus, but have no symptoms.
      12. After 6 weeks to 4 months, these people will develop anti-HIV antibodies--these are detected in AIDS screening tests.
      13. Eventually, people infected with the virus begin to have symptoms associated with viral infection.
      14. After 2 to 10 years, most people will have developed AIDS, the most serious form of HIV disease
      15. See timeline handout (paper or online) for progressive appearance of symptoms
      16. Phase/stages of HIV infection
        1. HIV enters body
        2. HIV binds to cells via CD4 receptors
        3. Infected cell begins to make more virus slowly
        4. No symptoms at this stage, no anti-HIV antibody, but virus is present
        5. After few weeks, immune system makes anti-HIV antibodies that can be detected by the AIDS screening test as soon as enough is present
        6. People remain asymptomatic for years, producing both anti-HIV antibody and HIV virus
        7. Eventually people begin to display symptoms (early HIV disease--clotting defects, decreased numbers of red and white blood cells
        8. Later, maybe as long as 9 to 15 years later, people display symptoms of more advance HIV disease (some opportunistic infections, reduction in helper-T lymphocyte numbers)
        9. As T lymphocyte numbers are reduced, susceptibility to infectious diseases increases, and eventually the person has fully developed AIDS
        10. See paper or online handout
      17. Symptoms and signs of HIV disease and AIDS
        1. Symptoms: weakness, fatigue, night sweats, fever, swollen lymph nodes, diarrhea, weight loss
        2. Neurological signs: memory loss, loss of coordination, depression, paralysis, possibly leading to death
        3. Opportunistic infections: systemic fungal infections, unusual Pneumocystis pneumonia, tuberculosis, etc.
        4. Rare form of skin cancer: Kaposi's sarcoma (not seen in all AIDS patients)
      18. Progression from HIV infection to AIDS
        Time from infection with HIV Percent who will have AIDS
        3 years 4%
        5 years 14%
        6 years 27%
        7 years 34%
        9 years 42%
        10 years 50%
      19. About 75% of AIDS patients die within 2 years after diagnosis (with fully developed AIDS)
      20. As of 6/2001, the CDC Surveillance Report on AIDS reported that
        1. Worldwide, there were 40 million people infected with HIV disease
        2. Worldwide, in 2001, 3 million people died of AIDS, including 1.1 million women and 580,000 children
        3. Worldwide, 48% of adult cases are in women
        4. 95% of adults with AIDS and 90% of new cases live in the developing world
        5. In the USA, in men, 50% of cases are attributable to male-to-male transmission, 23% are IV drug users
        6. In the USA, in women, 40% of cases are attributable to contact with infected men, and 27% are IV drug users
        7. Between 1996 and 1997, deaths from AIDS declined by 12%, probably due to better treatments now available
      21. HIV transmission
        1. Virus enters body through linings of vagina, rectum, urethra, mouth or openings in skin
        2. Body fluids that contain sufficient amounts of virus to infect another person: blood, semen, vaginal fluids, breast milk, colostrum (but not tears, saliva, or urine)
        3. Routes of infection
          1. Mother to fetus/newborn (HIV crosses placenta to cause intrauterine infection, or is transmitted during birth or breast feeding)
          2. Sexual intercourse (vaginal, rectal, or oral, with the receiving partner most at risk)
          3. Contact with blood, semen, or vaginal fluids (needles, sex, razors....)
        4. HIV is not transferred by casual contact at home or work, coughing or sneezing, sharing drinking glasses, kissing, biting or spitting unless blood is transferred, mosquitos, tears, using saunas/hot tubs, visiting spas or health clubs
        5. From lowest risk to highest (most likely to transmit HIV): abstinence, oral sex, vaginal sex with latex condom and foam, anal sex with latex condom, unprotected anal sex (receiving partner)
        6. What inactivates HIV? (drying (99% in 3 days), bleach, 70% ethanol, Lysol, hydrogen peroxide)
        7. See paper and online handout on chance of transmission of HIV after 1 or 500 acts of intercourse under various circumstances
      22. HIV vaccine?
        1. External and internal viral proteins in conventional vaccine have not provided protection from HIV infection
        2. Fusin protein might be useful in a vaccine
        3. Genetic "vaccines" may be useful eventually
      23. Treatments
        1. Most treatments block reverse transcriptase, a viral enzyme that converts viral RNA to DNA, necessary to use host cell's apparatus for making proteins
        2. Newer drugs decrease viral load by up to 70%, prolong life of AIDS patients, increase % of CD4-positive cells
        3. Combinations of drugs decrease the chance that patients will become resistant compared to use of a single drug
        4. Nucleotide reverse transcriptase inhibitors: prevent growth of DNA chain being synthesized from viral RNA (AZT, ddI, ddC, 3TC)
        5. Non-nucleotide reverse transcriptase inhibitors (directly inactivate RT enzyme, often used with nucl. RT inhibitor)
        6. Protease inhibitors (block action of a viral enzyme that cleaves larger inactive viral proteins into smaller active proteins--without protease, host cell produces noninfectious HIV, often combined with RT inhibitors)
        7. Complications and side effects include rashes, kidney and liver damage, drug resistance