Chapter 3
Patterns and Trends in HIV/AIDS Surveillance

DETERMINING THE NUMBER OF PEOPLE INFECTED WITH HIV

The Centers for Disease Control and Prevention (CDC), headquartered in Atlanta, Georgia, keeps track of the number of people in the United States who are infected with HIV, the virus that is generally acknowledged to be the cause of AIDS.

These CDC figures—which have always been acknowledged as estimates—have been criticized as being either too high or too low. Nonetheless, the historical continuity of the agency's data allows trend analyses to be done. Therefore, when viewed over a number of years, the figures provide a reasonable indication of the progress of the disease in the United States.

Estimates of HIV infection are important, as they directly influence public health, medical resource allocation, and political and economic decisions. Definitive figures are difficult to obtain because laws prevent testing for HIV without consent and permission. Furthermore, many people are understandably reluctant to participate in household surveys because of confidentiality concerns and fear of losing or failing to get insurance coverage.

Health officials contend that knowing the prevalence of HIV infections (prevalence is a measure of all cases of illness existing at a given point in time) is not as crucial as knowing whether the number of HIV infections is rising or falling. The rate at which people develop HIV/AIDS during a specified period of time is known as the incidence rate. Since there are no national studies to collect this data (not all states require reporting of new HIV cases), estimates are based on reports from states that mandate confidential reporting of HIV cases, along with other small studies and surveys. Officials with the CDC explain that a major problem has been the lack of knowledge about how many people have become infected prior to the beginning of the agency's regular collection of data. This would help to determine how the current incidence of HIV compares to previous years. Comparison of incidence rates is important because they are a direct measure of the rate at which individuals become ill and provide data to help estimate the risk or probability of illness.

The CDC data through December 2003 from the thirty-three states with confidential HIV reporting and adjusted estimates from reported cases in other states found that 174,639 people were living with HIV that have not yet progressed to AIDS. (See Table 3.1.) This is an increase from 127,058 reported through December 2000 and 161,976 as of December 2001. Of the 2003 total, 1,687 were children younger than thirteen years old (a drop from 2,905 in 2001) and 172,952 were adults and adolescents (an increase from 158,806 in 2001).

The CDC also compiles figures on the numbers of people living with AIDS. Through December 2003, 403,928 adults and adolescents were estimated to be living with AIDS, an increase from the reported 331,471 adults and adolescents through 2001. The number of children younger than thirteen living with AIDS through 2003 (1,942) was a drop from the 2,410 children through 2001. The December 2003 data also indicate that among U.S. territories, a total of 10,131 people were living with AIDS, an increase from the 10,096 reported through 2001. This total includes fifty-one children younger than thirteen (a decrease from eighty-two through 2001) and 10,080 adults and adolescents (9,749 through 2001).

AIDS CASE NUMBERS

The first cases of what came to be recognized as AIDS were reported in the United States in June 1981. Five young, homosexual males in Los Angeles were diagnosed with Pneumocystis carinii pneumonia and other opportunistic infections. By August 1989 approximately one hundred thousand cases of AIDS had been reported to the CDC. By December 1997 that number had risen to 641,086; of these, 390,692 people had died. As of December 2001 the total of all reported cases was 788,672; 467,910 of these people had died. Cumulatively through 2003 there were 872,629 reported cases of AIDS in the United States; 524,060 people had died of the disease. (See Table 3.2 and Table 3.3.)

During the mid-1990s the number of AIDS cases rose dramatically. This surge was not an actual numerical increase, but was due to the expanded 1993 AIDS surveillance definition, which added diseases and conditions that had not been part of the prior definition of AIDS. By the late 1990s the number of AIDS cases leveled off and began to decline, probably as a result of the increasing use of effective antiretroviral drugs that delay the progression of AIDS. The number of new cases reported between December 2001 and December 2003 (83,957, representing an annual average of 41,979) was higher than the 31,682 new cases reported between December 2000 and December 2001, but lower than the 42,156 new cases reported from December 1999 through December 2000, which in turn was lower than the 47,083 cases reported in the period from December 1998 through December 1999.

THE NATURE OF THE EPIDEMIC

The changes in the distribution of HIV illustrate the increasing diversity of those affected by the epidemic in the more than twenty years since AIDS was first diagnosed. In 1981 all of the 189 AIDS cases reported in the United States were males. Three-fourths of these were men who have sex with men (in the 2003 CDC surveys, this category has been changed to male-to-male sexual contact, or MTM) living in New York and California. In 1990, of the more than 43,000 AIDS cases reported by all states, approximately 30% were from New York and California, 11% were women, and about 2% were children. In 1999 the proportions of reported cases among women, African-Americans, Hispanics, and people exposed through heterosexual contact all increased. On the other hand, the percentage of reported cases among whites and MTM declined somewhat.

Regional Differences

AIDS cases have been reported in all fifty states, the District of Columbia, and four U.S. territories. But the distribution of cases is far from even. In 2003 the annual adult and adolescent AIDS incidence rates per one hundred thousand population in the United States and U.S. possession and territories (see Figure 3.1) varied from 10.5 in North Dakota to 1,833.2 in the District of Columbia (the same pattern was evident from 1999 to 2000). Most recently reported cases show a concentration on the East Coast (particularly Connecticut, Maryland, New Jersey, and Delaware, with respective rates of 243.9, 284.4, 239.3, and 235.6, and Florida, with a rate of 301.9). Also prominent were Puerto Rico (rate of 316.6) and the U.S. Virgin Islands (rate of 345.4). Figure 3.2 shows the corresponding HIV and AIDS rates for children younger than thirteen in 2003.

RATES IN MAJOR METROPOLITAN AREAS

The majority of AIDS cases are concentrated in larger metropolitan regions (the city and surrounding suburbs). Metropolitan areas with populations of five hundred thousand or more accounted for 81% of all reported cases between 2000 and 2001 and 84% of the cumulative totals since 1981 (cumulative totals include both those who have died and those still living). In 2002 and 2003 the metropolitan AIDS incidence rates per one hundred thousand people were highest on the coasts, such as in New York City (60.1 and 59.2, respectively), Miami (49.2 and 45.8), Baltimore (48.4 and 39.3), Jersey City, New Jersey (32.6 and 28.3), Fort Lauderdale, Florida (44.0 and 39.9), West Palm Beach, Florida (48.1 and 36.7), Baton Rouge, Louisiana (49.4 and 33.7), Newark, New Jersey (27.6 and 25.8), Columbia, South Carolina (37.0 and 33.5), and San Francisco (31.9 and 45.2). On the other hand, Midwest metropolitan areas displayed the lowest rates: Akron, Ohio (4.1 and 3.4), Grand Rapids, Michigan (4.7 and 4.4), and Youngstown, Ohio (4.1 and 4.3). Ann Arbor, Michigan, had the lowest overall metropolitan rate (3.0 and 3.3), followed by Salt Lake City, Utah (3.8 and 4.3), and Scranton, Pennsylvania (3.9 and 5.4). (See Table 3.4.)

There are several reasons for the higher rates in urban areas. First, metropolitan areas are more cosmopolitan and, by definition, more tolerant of alternative lifestyles such as those of MTM, a group with high-risk sexual behaviors. Second, large metropolitan areas also have greater numbers of intravenous drug users (IDUs), another major risk factor for HIV infection. Third, while HIV infection and transmission are not restricted to more populated areas, those who need and seek treatment may

migrate to these areas for access to medical care and social services. In many smaller communities medical care may be unavailable and financial and/or social barriers may limit access to health care services.

Rates among MTM: A Decline?

Table 3.5 displays CDC data on reported AIDS cases by age category, transmission category, and sex. The CDC reported 44,811 new adult and adolescent AIDS cases from January through December 2003, an increase from the 42,983 and 41,960 cases during the same periods in 2001 and 2000, respectively. Of the 2003 total, 33,250 were adult and adolescent males (compared with 31,901 in 2001 and 31,501 in 2000). Of these males, the portion attributable to transmission among MTM who did not also inject drugs was 15,859 cases (48% of total) in 2003, representing an increase from the 13,265 cases (42%) in 2001 and 13,562 cases (43%) in 2000. Since an additional 4,866 (15%) of MTM in 2003, 1,502 (5%) in 2001, and 1,548 MTM (5%) in 2000 also used intravenous drugs, it is unclear whether AIDS was acquired from sexual behavior or intravenous drug use. Examination of data from 1981 (when record keeping began) until December 2003 reveals that men in the MTM exposure category who did not use intravenous drugs accounted for 55% of all men who had acquired AIDS and 45% of all reported AIDS cases. This latter percentage is slightly less than the cumulative 46% in both 2001 and 2000.

Rates among Women

In 2003 reported AIDS cases among women that were attributable to intravenous drug use (2,262) comprised 20% of the total number of cases (11,561), as compared with 2,212 cases in 2001 (20% of 11,082 cases). In 2000, 2,609 cases (25% of the total of 10,459 cases) represented intravenous drug use. With respect to intravenous drug use, previous percentages were 23% in 1998 and 1999, and 19% in 1995. The actual number of cases remained fairly constant from 1994 to 1997—13,887 in 1994, 13,764 in 1995, 13,767 in 1996, and 13,105 in 1997—then dropping to 10,998 in 1998–99 and 10,459 in 2000 before increasing to 11,082 in 2001 and 11,561 in 2003. (See Table 3.5.)

When considering the role of heterosexual contact in the acquisition of AIDS, the proportion was far higher for women in 2003 (5,234 cases, representing 45% of the total of 11,561) than for men (3,371, representing 10% of the total of 40,947). Women with a history of heterosexual contact as their only risk factor made up 37% of all female cases in 2001. In contrast, 9% of men acquired HIV through heterosexual contact in 2001.

Decline in AIDS Due to Blood Transfusions

As a result of screening procedures for blood and blood products that began in 1985, the number of AIDS cases among adult and adolescent transfusion recipients decreased between 1995 (664 cases) and 1997 (409 cases). A pronounced decrease between 1998 and 1999 (266 cases) has been followed by 282 cases in 2000, 218 cases in 2001, and 219 in 2003. (See Table 3.5.)

The number of AIDS cases among adults and adolescents with hemophilia has also decreased. In 1996, 330 cases were reported. In 1997, 201 cases were reported. The number of new cases among hemophiliacs declined to 171 in 1999, 96 in 2000, 106 in 2001, and 85 in 2003. (See Table 3.5.)

Current Age and Gender Distribution

Of the 902,223 cumulative total reported cases of AIDS in 2003, 892,875 (99%) were among adults and adolescents. (See Table 3.5.) The remaining 9,348 cases (representing 1% of the cumulative total) were children under the age of thirteen. According to the CDC, which has distinct case definitions for the two age groups, as of December 2003 more people between the ages of thirty-five and forty-four were living with either HIV or full-blown AIDS (168,322; 41.5% of all cases) than in any other age category. (See Table 3.6 and Table 3.7.)

Cumulatively, the total number of AIDS cases that were reported in adults and adolescents in 2003 occurred predominantly in males (729,478 cases). (See Table 3.5.) Adult and adolescent females accounted for 163,396 cumulative cases (18.6% of the total). (See Table 3.5.)

Race or Ethnicity and AIDS

The changing racial/ethnic profile characteristics of Americans with AIDS from 1993 through 2001 reflect a shift in the population at risk for HIV/AIDS. In 1993 there were 60,587 cases reported among African-Americans. By 2000 the number of cases had reached 135,562. (See Table 3.7.) The number of cases among African-Americans has grown steadily since (146,057 in 2001, 156,771 in 2002, and 167,938 in 2003). The corresponding case figures for non-Hispanic whites are 80,185 in 1993, 113,617 in 2000, 120,186 in 2001, 127,257 in 2002, and 134,678 in 2003. The number of AIDS cases among African-Americans has exceeded those among whites from 1998 through 2003.

In 1999 African-Americans accounted for 40.6% of people estimated to be living with HIV/AIDS. This figure rose to 47.7% in 2001 through 2003. In contrast, the proportion of non-Hispanic whites living with HIV/AIDS went from 38.5% (1999) to 39.2% (2001), 38.7% (2002), and 38.3% (2003).

In 2003 Hispanics accounted for 9,133 new reported AIDS cases. Corresponding figures for whites and African-Americans were 13,612 and 21,064, respectively. The total number of male and female adult and adolescent reported AIDS cases in Asian-Americans/Pacific Islanders (558) and Native Americans/Alaska Natives (220) were the lowest of all racial/ethnic groups in the United States. (See Table 3.8 and Table 3.9.)

In 2003 the total (male and female) reported AIDS incidence rate per one hundred thousand adults and adolescents among African-Americans (75.2) was more than ten times higher than that among non-Hispanic white Americans (7.2), more than seven times than that of Native Americans/Alaska Natives (10.4), and almost three times that of Hispanics (26.8). Rates were lowest among Asian-Americans/Pacific Islanders (4.8). (See Table 3.10.)

The racial and ethnic difference is particularly alarming among children under the age of thirteen. As shown in Table 3.10, in 2003 the rate of HIV per one hundred thousand population for African-American children (0.5) was five times the rate for Hispanic children (0.1). The other categories were negligible.

The racial disparity is also reflected in the acquisition of HIV/AIDS by infants born to HIV-infected mothers. In the years 2000 through 2003 the number of reported cases of HIV/AIDS among African-American infants has been a minimum of four times greater than the reported cases for non-Hispanic whites and Hispanic infants born to HIV-infected mothers. (See Table 3.11.)

HOW HIV IS TRANSMITTED

HIV can be transmitted by sexual contact with an infected person; by needle sharing among infected intravenous drug users; through the receipt of infected blood, blood products, or tissue; and directly from an infected mother to her infant during pregnancy, delivery, or breastfeeding.

In the United States MTM remain the majority of HIV carriers, although prevalence among heterosexuals is on the rise. In 1987, 70% of adult and adolescent males with AIDS had a single risk factor of a history of highrisk sexual activity. The proportion of affected MTM has dropped to 45% (2001 through 2003). Adult and adolescent males with a history of intravenous drug use as their only risk factor made up 14% of all cases in 1987. This proportion has changed only marginally in the intervening years, remaining relatively stable at 15% in 2003. (See Table 3.9.)

The proportion of adult and adolescent females with AIDS whose only risk factor was intravenous drug use has dropped from 50% in 1987 to 39% in 2001. Adult and adolescent females with a history of heterosexual contact as their only risk factor made up 38% of all female cases in 1997. By 2001 that proportion increased to 41%, and through 2003 has increased to 45%. (See Table 3.8.) Researchers suggest that one reason for steadily increasing HIV infection and AIDS among heterosexuals is that an increased proportion report multiple sex partners, which is a risk factor for HIV infection.

Undetermined Risk

In 2003 there were 11,220 adult and adolescent (both male and female) cases of AIDS with an undetermined risk. (See Table 3.5.) That is, there was no reported history of exposure to HIV through any of the routes listed in the exposure categories. These include people currently being investigated by local health departments, people whose exposure history was incomplete at the time of their death, those who refused to be interviewed or whose cases were not followed up, and those who were interviewed but no follow-up occurred. When an exposure mode is identified during follow-up, patients are reclassified into the appropriate exposure category.