ePathoPlusPage

HIV/AIDS

Outline

A. Epidemiology

B.. Structure of HIV

    a. retrovirus, characteized by presence of reverse transcriptase

    b. infects CD4 cells and macrophages

C. Transmission

    a. sexual contact

    b. blood exchange

    c. perinatally

        1. in utero

        2. during labor and delivery    

        3. through breast milk

D. Stages of HIV/AIDS

    a. primary HIV infection

    b. seroconversion

    c. clinically latent period

    d. early symptomatic HIV infection (ARC or B symptoms)

    e. AIDS (presence of AIDS Indicator conditions)

    f. Advanced AIDS (CD4 < 50)

E. CDC Classification

F. Some of the most frequent opportunistic infections

    a. pneumocystis carinii pneumonia (PCP)

    b. Mycobacteriuim tuberculosis

    c. Mycobacterium avium intracellulare (MAI)

    d. Cytomegolivrus (CMV) retinopathy

    e. Toxoplasmosis gondii

    f. Cryptococcus neoformans

    g. Herpses simplex virus (HSV) esophagitis

     h, Esophageal candidiasis

    i. cryptosporidiosis

    j. AIDS dementia

    k. peripheral neuropathy

    l. Wasting syndrome

    m. Kaposi's sarcoma

Discussion  

    Once infected with HIV, the virus remains in the individual for a lifetime.This is similar to the pattern of infectivity found in other viruses, for example the virus that causes chicken pox (herpes zoster virus). Unlike many other viruses, HIV tends to reamain more active then latent. The typical clinical course is one in which each day millions of  infected CD4 cells are killed (mostly by the body's own immune system as it tries to rid itself of the virus) and billions of new HIV are produced, infecting more CD4 cells. Gradually, (for it is war of attrition), the body cannot replace CD4 cells as quickly as they are being destroyed, so the overall CD4 count begins to drift down. In an untreated patient it typically takes 10 years for the CD4 count to go from a normal of approximately 1,000 to a level of 200. At this level you begin to get the onset of opportunistic infections because of the tremendous impairment to the immune system. Because the virus is always present, a person once infected with HIV remains potentially infectious to other people for the rest of their life, even if they are not having any symptoms suggestive of illness.
Recently, a new type of aggresive therapy has been instituted to combat HIV/AIDS. It is called Highly Active Anti-retroviral Therapy (HAART) and consists of a regimen of at least three drugs, ususally two nucleoside reverse transcriptase inhibitors such as zidovudine (retrovir) and lamivudine (Epivir) and one protease inhibitor such as Crixivan. The drugs do not kill the virus (no drug is available that can directly kill a virus), what they do is disable different parts of it's life cycle, thus inhibiting replication of the virus. The nucleoside reverse transcriptase inhibitors inhibit reverse transcriptase and the protease inhibitors inhibit protease. HAART has been very successful in many HIV/AIDS patients in lowering their viral load (quantitative measurtement of the amount of HIV detectable in the blood) and thus relieving symptoms and slowing progression of the illness. But, to date, it has not been effective in eliminating the virus completely from the body.Experience shows that in those individuals whose viral loads are zero due to HAART and, who then stop taking the medications, their viral load shoots up again.   In addition, these drugs have practical consequences: 1. they do not work in everyone, 2. they have serious side effects, 3 they require compliance to a difficult regimen of pill taking (drugs must be taken every day, several times a day), 4. they are very expensive and 5. there is the real posiibility that HIV can and may become resistant to thes drugs.

      Clinically  

    Experts at UNAIDS estimate that worldwide more than 30 million people are infected with HIV but that less than 10% of them know it.. In the US, the fastest growing mode of transmission for HIV is heterosexual intercourse and the increase is fastest among woman. In 1985 woman accounted for 7% of the total of those infected in the US, in 1996 they accounted for 19%, with a six fold increase from 1991 to 1995 alone. Healthcare workers need to be alert for those at risk for HIV and recommend testing. According to the CDC, people falling into the following categories should be tested:
1. People with sexually transmitted diseases
2.Those in high risk categories such as
    a. injection drug users
    b. gay and bisexual men
    c. hemophiliacs
    d. regular sexual partners of of persons in thos ecategories and persons with known HIV infection
3. Those in lower risk categories susch as
    a. prostitutes
    b. persons who received blood products from 1977 - May, 1985
    c. heterosexual [ersons with > one sex partner in past 12 months plus non compliance with condom use in the past 6 months
4. persons who consider themselves at risk or who request the test
5. pregnant woman
6. patients with active tuberculosis
7.recipients and source of occupational exposures
8. hospital admissions for patients aged 15 -54 years where seroprevalence rates exceed 1% or AIDS cse rates exceed 1/1,000 discharges
9. Healthcare workers who perform exposure prone invasive procedures depending on institutional policy
10. donors of blood, semen and organs
11. medical evaluation for clinical or laboratory findings suggestive of HIV infection (e.g. generalized lymphadenopathy, unexplained dementia, aseptic meningitis or peripheral neuropathy, chronic, unexplained fever, diarrhea or weight loss, oersistent herpes simplex, herpes zoster if disseminated or involves more than one dermatome, thrush, oral hairy leukoplakia, opportunistic tumors, unexplained cytopenias.
    The efficacy of transmission in health care wokers (those exposed occupationally as might occur with a needlestick injury) is 0.25% - 0.3% as documented in 14 studies as well as with CDC experience in > 3,000 exposures. Healthcare workers have a much greater risk of contracting tuberculosis as a result of occupational exposure to those with active TB then they do in contracting HIV.