Confronting AIDS Directions for Public Health, Health Care, and Research (1986) / Chapter Skim
Currently Skimming:
2. Understanding of the Disease and Dimensions of the Epidemic
2. Understanding of the Disease and Dimensions of the Epidemic
Pages 37-84
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 37... ...
drug users, recent Haitian immigrants, hemophiliacs, recipients of blood transfusions, sexual partners of persons who had the disease or were at risk, and infants of mothers with the disease or at risk. As a result, the general term "acquired immune deficiency syndrome" (AIDS)
|
From page 38... ...
. Initially, 11 opportunistic infections and diseases were considered specific enough to be diagnostic for AIDS.
|
From page 39... ...
Initial attempts to isolate novel retroviruses from persons with AIDS were stymied by an inability to grow the cells in which human retroviruses proliferate a type of white blood cell known as a T lymphocyte. Rather than continuing to proliferate, T lymphocytes derived from AIDS patients showed short-term growth and then extensive cell death.
|
From page 40... ...
Testing of sera from AIDS patients and persons with AIDS-associated conditions disclosed the presence of antibodies reactive with the protein constituents of HIV in almost all instances, whereas sera from individuals not in "at risk" groups were uniformly negative (Brun-Vezinet et al., 1984; Safai et al., 1984; Sarngadharan et al., 19841. Serum samples from individuals in groups at risk for the development of AIDS demonstrated a prevalence of antibodies to HIV that correlated well with the time of appearance, extent, and geographic clustering of cases of AIDS and ARC.
|
From page 41... ...
But it was not until 1980 that a retrovirus was definitively isolated in a human disease, an unusual type of T-cell leukemia (Poiesz et al., 19801. This retrovirus, human T-cell lymphotropic virus type I (HTLV-I)
|
From page 42... ...
Retroviruses isolated from the affected animals shared many biologic and immunologic characteristics with HIV. These related viruses have been named STLV-III (for simian T-cell lymphotropic virus type III)
|
From page 43... ...
Normally, the CD4-to-CD8 ratio in humans is 1.5 to 2.0. In AIDS patients, however, this ratio is inverted, so that it is less than 1.0.
|
From page 44... ...
The immunodeficiency of AIDS clearly demonstrates the importance of CD4 T lymphocytes. Because of the loss of these cells, the remaining T lymphocytes from AIDS patients have diminished or absent responses to antigens, to certain chemicals known as mitogens that make T cells divide, and to blood cells from nonidentical individuals.
|
From page 45... ...
during AIDS may be due to the migration of infected cells, such as macrophages, into the sites, or to infection of these cells in situ. It is not known what proportion of individuals who are seropositive for HIV antibodies will ultimately develop clinical AIDS (see Chapter 31.
|
From page 46... ...
(See Appendix A for a more detailed discussion of the presentation, diagnosis, and treatment of the clinical manifestations of HIV infection.) The current CDC definition of AIDS reflects those opportunistic infections and cancers observed in the United States.
|
From page 47... ...
Second, they are among the most common causes of death in AIDS patients. Opportunistic infections that have assumed a major role in the epidemic include Pneumocystis carinii pneumonia; toxoplasmosis; tuberculosis; viral infections due to herpes simplex, herpes zoster, and cytomegalovirus; cryptococcal disease (especially meningitis)
|
From page 48... ...
In 1985 this observation led the CDC to add this disease, when accompanied by a positive serologic test for HIV antibodies, to the surveillance definition of AIDS. Non-Hodgkin's lymphoma related to HIV infection occurs at unusual sites for that diseasee.g., the central nervous system, the rectum, and gastrointestinal sites.
|
From page 49... ...
They include the timing and frequency of infection, the amount of time that may elapse between involvement of the central nervous system and the development of subacute encephalitis with dementia, and the primary site of infection in the central nervous system. The answers to these questions will have major implications for the design of future therapeutic agents, which will have to cross the blood-brain barrier; for social, ethical, and legal issues involving AIDS; and for the planning of future health care for AIDS patients.
|
From page 50... ...
Knowledge of the routes of transmission of infectious agents in human populations is derived primarily from epidemiologic data. Direct evidence related to the efficiency of specific routes of HIV transmission cannot be derived experimentally, because it is unethical to deliberately infect a human being.
|
From page 51... ...
and having a number of sexual partners as the primary risk factors for HIV infection in homosexual men. Among men who practice receptive anal intercourse, rectal douching appears to further increase the risk, probably through trauma to the rectal mucosa or damage to normal protective barriers (W.
|
From page 52... ...
Parenteral Transmission Epidemiologic data have indicated parenteral HIV transmission in a number of populations, including IV drug users, hemophiliacs, and blood transfusion recipients. IV drug users commonly share injection paraphernalia (syringes and needles)
|
From page 53... ...
Of greatest concern to the general public is the risk of HIV transmission from packed red blood cells, which are the blood component most frequently transfused (although the much smaller number of patients who
|
From page 54... ...
Under slightly more pessimistic assumptions, the risk rises to approximately 1 in 11,000. With the risk of HIV transmission to blood recipients reduced by more than 95 percent through antibody testing, instead of 4,000 infected units out of 10 million used, the baseline calculations presented in Appendix C project the transfusion of about 100 infected units each year.
|
From page 55... ...
Questions have been raised about the possibility of HIV transmission from two other blood products: immune globulins and plasma-derived hepatitis B vaccines. The Centers for Disease Control actively monitors reported AIDS cases for evidence of an association with immune globulin.
|
From page 56... ...
One case of HIV transmission to an infant via breast milk has recently been reported, suggesting the possibility that the virus could be transmitted orally to infants through breast-feeding (Ziegler et al., 1985~. This issue would be of special importance in the developing countries of central Africa, where breast-feeding is otherwise extremely desirable.
|
From page 57... ...
POPULATION GROUPS AT INCREASED RISK OF HIV INFECTION In the United States, homosexual males, IV drug users, neonates born to infected mothers, and persons such as hemophiliacs who received pooled blood products, including clotting factor, before testing for HIV antibodies have the highest risk of acquiring HIV infection. These groups have the most cases of AIDS and the highest prevalence of seropositivity.
|
From page 58... ...
One study estimates that from 70,000 to 100,000 homosexual men reside in San Francisco, nearly a quarter of all of that city's male population aged 15 and over. Los Angeles, New York City, and Chicago probably have even larger numbers of homosexual men.
|
From page 59... ...
Intravenous Drug Users The second-largest risk group for AIDS in the United States is IV drug users. According to the Centers for Disease Control, 17 percent of reported AIDS cases currently occur in people whose only known risk factor is IV drug use.
|
From page 60... ...
Blacks, who make up approximately 13 percent of the nation's population, are nearly 40 percent of the IV-drugusing population (Ginzburg and Weiss, 19861. In prison populations, IV drug users are known to be overrepresented, because IV drug use is an important factor predisposing to crime and incarceration.
|
From page 61... ...
. Heterosexual Contacts of HIV-Infected Persons The heterosexual contacts of persons infected with HIV include heterosexual partners of IV drug users, female sex partners of bisexual men, sexual partners of infected hemophiliacs or of persons infected through transfusions, clients of infected prostitutes, and the heterosexual partners of other infected individuals.
|
From page 62... ...
Infants who acquire their infection from an infected mother are generally the offspring of female IV drug users, female sexual contacts of male IV drug users, female sexual partners of bisexual males, and women from Haiti or central Africa. As HIV infection continues to spread within the general heterosexual population, it would be expected that more children infected with HIV will be born to women with multiple sexual partners or to women whose male sexual partners have had contact with multiple sexual partners.
|
From page 63... ...
As of early 1986, about 4 percent, or almost 800, of the more than 20,000 reported AIDS cases in the United States had occurred among health care workers. This percentage is similar to the proportion of the population employed in health care.
|
From page 64... ...
Such concerns undoubtedly lead to underreporting on death certificates, but this would have a more negative effect on research projects using death certificates than on national surveillance data. With the increasing availability of the HIV antibody test to assist in determining infection status, there have been anecdotal reports that skin biopsies to diagnose Kaposi's sarcoma definitively and bronchoscopy to diagnose Pneumocystis carinii pneumonia are being obtained less frequently.
|
From page 65... ...
As with ARC, the CDC has not requested national reporting of asymptomatic HIV infections. Nevertheless, a few states have followed Colorado in requiring the reporting of persons who have tested positive for HIV antibodies.
|
From page 66... ...
Case-control studies carried out during the past few years have provided valuable information on specific risk factors associated with AIDS in different population groups. In one of these studies the CDC compared male homosexual AIDS patients to healthy homosexual men selected from outpatient clinics and the practices of private physicians (Jaffe et al., 19831.
|
From page 67... ...
In contrast to the cohorts from the other four cities, the San Francisco cohort was recruited from a probability sample and thus can be considered representative of the census tracts from which it was drawn. The other cohorts were recruited mostly from sexually transmitted disease clinics and from advertisements directed to homosexual populations.
|
From page 68... ...
Because of concerns over this issue, some jurisdictions have passed very strict consent and disclosure laws to prevent potential misuse of these tests. Thus, the routine testing of persons attending public sexually transmitted disease clinics cannot be carried out in many areas without the specific, written consent of the person to be tested.
|
From page 69... ...
From studies of HIV infection among homosexual men and IV drug users, it is clear that a large number of persons in the two largest AIDS risk groups have been infected. Using estimated prevalence of infection and estimates of the size of these risk groups, estimates of the total number of infected persons in the United States can be derived.
|
From page 70... ...
The doubling time for AIDS cases has increased from about four months in 1981 to almost one year in 1985-1986. A total of 23,426 of the adult AIDS patients have been identified as being in one of the known HIV transmission categories: homosexual men with a history of drug abuse (8 percent)
|
From page 71... ...
This proportional change is greatest relative to New York City. It is primarily among homosexual men, but it is also seen among IV drug users and in the remaining risk groups.
|
From page 72... ...
The slight increase in the age of AIDS patients does not necessarily indicate an increasing rate of new infection among older persons. AIDS Case Trends in Disease Presentation and Mortality Pneumocystis carinii pneumonia (PCP)
|
From page 73... ...
Approximately 55 percent of all AIDS patients reported to the CDC are known to have died. The reported one-year mortality is 48 percent and increases to approximately 75 percent two years after the initial diagnosis is made (Centers for Disease Control, 1986c)
|
From page 74... ...
Clinically, AIDS cases in Africa differ from those in North America and Europe. There is a paucity of instances of documented Pneumocystis carinii infections in Africa, and a high frequency of oral candidiasis and tuberculosis, especially extrapulmonary (Bigger, 1986; Mann et al., in press)
|
From page 75... ...
Furthermore, seropositivity has been found in 31 to 66 percent of Nairobi women who are prostitutes and in 8 percent of men attending a Nairobi clinic for sexually transmitted diseases, in contrast to 2 percent of medical personnel (Kreiss et al., 19861. A survey of seropositivity in household contacts of AIDS patients and controls in Kinshasa showed a statistically significant increase in the seropositivity rate in spouses (61 percent in cases versus 4 percent in controls)
|
From page 76... ...
The pattern of AIDS in Europe largely mirrors that in the United States. A large proportion of cases occur in homosexual men and IV drug users, with small numbers in heterosexual partners of people in high-risk groups, recipients of blood products, and travelers from countries with
|
From page 77... ...
1985. Transient antibody to lymphadenopathy-associated virus/human T-lymphotropic virus type III and T-lymphocyte abnormalit~es in the wife of a man who developed the acquired immunodeficiency syndrome.
|
From page 78... ...
1986b. Recommendations for assisting in the prevention of perinatal transmission of human T-lymphotropic virus type III/lymphadenopathy associated virus and the acquired immunodeficiency syndrome.
|
From page 79... ...
1985. Antibody seronegative, HTLV-III infected patients with acquired immunodeficiency syndrome or related disorders.
|
From page 80... ...
1985b. Infection with HTLV-III/LAV and transfusion associated acquired immunodeficiency syndrome.
|
From page 81... ...
1986. Long-term seropositivity for human T-lymphotropic virus type III in homosexual men without the acquired immunodeficiency syndrome: Development of immunological and clinical abnormalities.
|
From page 82... ...
1984. Seroepidemiological studies of human T-lymphotropic retrovirus type III in acquired immunodeficiency syndrome.
|
From page 83... ...
1984. Acquired immunodeficiency syndrome in Rwanda.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.