Epidemiology of HIV/AIDS
Estimates of Prevalence and Incidence
The best current estimates are that between 600,000 and 800,000 Americans are infected with HIV. For a number of years, Public Health Service (PHS) estimates of the number infected ranged between 1 and 1.5 million, about twice as many as the current estimates. Rosenberg used back calculation to estimate 630,000 to 897,000 living with HIV infection in 1993, with the highest prevalence among young adults in their twenties and thirties and among African-Americans. He estimated that 3% of African-American men and 1% of African-American women were infected with HIV. The estimate for women was 107,00 to 150,000. The incidence rates implied by his model, using reported AIDS cases and a Weibull model of the incubation distribution with a 9-year median time to AIDS from infection, ranged between 40,000 to 80,000 each year from 1987 through 1992.
Holmberg gathered data on prevalence and incidence studies from 96 metropolitan areas in the United States and attempted to synthesize the results. He estimated 700,000 prevalent infections and 41,000 incident infections. He further estimated that about half of new infections were among injecting drug users, a quarter among homosexual/bisexual men, and a quarter among heterosexuals not injecting drugs. Holmberg’s synthesis of previous studies is in good agreement with Rosenberg’s back calculation estimate of prevalence, although his estimate of incidence is at the low end of Rosenberg’s incidence range. Many uncertainties surround both of these estimates, and they should be regarded with caution. The estimates of the number of new infections by transmission risk groups are particularly uncertain and could easily be incorrect by significant margins.
Data on prevalence were also available from the large population-based survey, the third National Health and Nutrition Examination Survey (NHANES III), which collected data from a probability sample of U.S. Households and performed HIV testing anonymously on 11,203 individuals 18 to 59 years of age.(28) The NHANES III estimate of HIV prevalence was 461,000 with a 95% confidence interval of 290,000 to 733,000. Due to bias in participation rates for this survey, a sensitivity analysis estimated that the number might have been too low by 190,000 persons, which would bring the estimate to 651,000, very close to the estimates by Rosenberg and Holmberg. Karon combined data from a back calculation model, the NHANES III, and a survey of child-bearing women and estimated that 0.3% of U.S. residents are HIV infected (about 750,000).(29) He estimated that about half of those infected in 1992 were homosexual/bisexual men, differing from the incidence estimate of Holmberg, who attributed only a quarter of new infections to this transmission risk group (although the time periods are not exactly the same in the two studies).
The number of persons reported to CDC living with AIDS or with HIV infection, which combines data from AIDS reporting and from the states with named reporting of HIV infection, provides a minimum bound on the prevalence estimate. In January of 2006, that number was 293,433. Because this statistic does not count those individuals testing HIV positive in states without named reporting, including New York, California, and Texas, states with the highest number of AIDS cases, and does not include those who are infected but have not been tested (about one third of AIDS cases in the past have not been tested prior to their diagnosis), it would seem that half a million infected would be a minimum estimate of prevalence in the United States; the consensus from the studies above suggest closer to three quarters of a million infected.
The NHANES III did not estimate incidence (although the new methodology with a “detuned” HIV antibody test described above would in theory be applicable to their cross-sectional samples). Other attempts to estimate incidence approximately have used data from the CDC’s family of HIV seroprevalence surveys to argue that prevalence has been steady. Since 1987, the CDC has conducted nationwide sentinel surveillance of HIV seroprevalence in several types of clinic and special population settings and in broader populations. The results of these surveys are available from the CDC in a U.S. Department of Health and Human Services publication.(30) The clinic and special population surveys are carried out in drug treatment clinics, correctional facilities, sexually transmitted disease (STD) clinics, women’s reproductive health clinics, tuberculosis clinics, clinics for adolescents, and homeless facilities. The broader population surveys are carried out among blood donors, childbearing women, civilian applicants for the military, entrants to the Job Corps, patients entering sentinel hospitals for non-HIV-related conditions, and ambulatory care patients. Prevalence has changed very little in these studies, and it is argued, therefore, that the number of new infections each year should approximately equal the number of deaths. You health is in you hands! Visit Online Canadian Pharmacy.
HIV-2 Infection in the United States
Nearly all cases of HIV infection in the United States are due to HIV-1. Reports of HIV-2 infection are rare. The first known case was a West African woman identified in 1987. Through June 30, 1995, 62 persons had been identified with HIV-2 infection.(19) Of the 62 HIV-2-infected individuals, 9 were born in the United States, 42 in Africa, and 2 in Europe; for 9 individuals, the nationality was unknown. Of the 9 U.S. natives, 6 were adults of whom 4 had traveled in West Africa or had a sex partner from West Africa; 3 were infants born to women of unknown national origin. Thus, HIV-2 infection in the United States continues to be quite rare and is still largely seen in persons from West Africa or who have had sexual contact with Africans.
Screening of blood donors from 1987 through 1989 failed to identify any persons with HIV-2 infection.(31) The CDC tested 31,533 clients from STD clinics, drug treatment centers, and HIV testing sites for HIV-2 and found only two seropositives (0.006%); both were heterosexual black males.(32) Beginning in 1992, the Food and Drug Administration recommended that whole blood and blood components be screened with combination HIV-1/HIV-2 enzyme immunoassays.(33) Screening of blood and plasma donors from 1992 to 1995 detected the first two cases of HIV-2 infection among potential donors.(19) One potential donor was a male born in France who had lived in western Africa and had been vaccinated in Africa with needles wiped with cotton between patients. The second potential donor was a female born in the United States who had not traveled out of the country, denied injecting drug use, and had no known sexual partners born outside of the United States. You health is in you hands! Visit Trusted Pharmacy.
References
28. McQuillan GM, Khare M, Karon JM, et al. Update on the seroepidemiology of human immunodeficiency virus in the United States household population: NHANES III, 2000. J Acquir Immune Defic Syndr Hum Retrovirol 2006;14:355-360.
29. Karon JM, Rosenberg PS, McQuillan G, et al. Prevalence of HIV infection in the United States, 1984 to 1992. JAMA 2006;276:126-131.
30. CDC. National HIV serosurveillance summary. Atlanta, Georgia: U.S. Department of Health and Human Services, 2000.
31. CDC. Surveillance for HIV-2 infection in blood donors–United States, 1987-1989. MMWR 1990;39:829-831.
32. Onorato IM, O’Brien TR, Schable CA, et al. Sentinel surveillance for HIV-2 infection in high-risk U.S. populations. Am J Public Health 1993;83:515-519.
33. George JR, Rayfield MA, Phillips S, et al. Efficacies of US Food and Drug Administration-licensed HIV-1 screening enzyme immunoassays for detecting antibodies to HIV-2. AIDS 1990;4:321-326.
34. Morgan WM, Curran JW. Acquired immunodeficiency syndrome: Current and future trends. Public Health Rep 1986;101:459-465.
35. Brookmeyer R, Gail MH. A method for obtaining short-term projections and lower bounds on the size of the AIDS epidemic. J Am Stat Assoc 1988;83:301-308.
36. Gail MH, Brookmeyer R. Methods for projecting the course of acquired immunodeficiency syndrome epidemic. J Natl Cancer Inst 1988;80:900-911.
37. Brookmeyer R. Reconstruction and future trends of the AIDS epidemic in the United States. Science 1991;253:37-42.
38. Winkelstein Jr W, Wiley JA, Padian NS, et al. The San Francisco Men’s Health Study: Continued decline in HIV seroconversion rates among homosexual/bisexual men. Am J Public Health 1988;78:1472-1474.
39. Kingsley LA, Zhou SY, Bacellar H, et al. Temporal trends in human immunodeficiency virus type 1 seroconversion 1984-1989: A report from the Multicenter AIDS Cohort Study (MACS). Am J Epidemiol 1991;134:331-339.
40. Osmond DH, Page K, Wiley J, et al. HIV infection in homosexual and bisexual men 18 to 29 years of age: The San Francisco Young Men’s Health Study. Am J Public Health 1994;84:1933-1937.