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Tuberculosis (TB) remains an important public health problem worldwide, resulting in a estimated 8 to 10 million new cases and 2 to 3 million deaths each year. Between 1953 and 1985, the number of TB cases in the US declined by an average of 6% per year. However, since 1985, TB has been increasing in the US. Approximately 64,000 additional cases of the disease have been reported beyond the number expected had the rate of decline observed from 1980 to 1984 continued from 1985 through 1993. Increases in the number of TB cases have been significant in racial and ethnic minorities, in persons born outside the US, and in children less than 15 years of age. Infection with the human immunodeficiency virus (HIV) has also been recognized as a major risk factor for the development of active TB in persons with latent Mycobacterium tuberculosis infection. The unusual radiographic findings and the increased likelihood of extrapulmonary TB in HIV-infected persons make diagnosis of the disease problematic. Lastly, concomitant with the resurgence of TB has been the emergence of drug resistance. All of these factors make successful control of TB in the US difficult.

Objective: To evaluate the effect of human immunodeficiency virus (HIV) infection and tuberculosis on hospitalizations and the cost of care., Design: National Hospital Discharge Survey, a nationally representative survey of discharges from U.S. nonfederal short-stay hospitals, and statewide billing information., Patients: Patients 15 to 44 years of age with a listed diagnosis of HIV infection (n = 418,200) or active tuberculosis (n = 77,700) during 1985-1990., Results: During 1985-1990, hospitalizations related to HIV infection increased sixfold, from 18 to 102 per 100,000 persons; during 1988-1990, hospitalizations related to tuberculosis increased twofold, from 8 to 16 per 100,000 persons. The prevalence of tuberculosis among HIV-infected patients increased from 2.4% in 1985-1988 to 5.1% in 1989-1990 (P = 0.003). The prevalence of HIV infection among patients with tuberculosis increased from 11% in 1985-1988 to 28% in 1989 to 39% in 1990 (P < 0.001). Infection with HIV was more prevalent among patients with extrapulmonary tuberculosis (31%) than among those with pulmonary tuberculosis (18%) (P = 0.01). An increase in the duration of hospital stay was associated with both tuberculosis and HIV infection. From 1985 to 1990, inpatient care costs increased 7.7-fold and 3.2-fold for HIV and tuberculosis hospitalizations, respectively. During this period, HIV and tuberculosis hospitalizations resulted in 5,793,000 and 1,107,900 days of care, respectively, with an estimated direct cost of $5.7 to $7.4 billion and $0.89 to $1.07 billion, respectively. Estimated national costs of inpatient care for HIV infection or tuberculosis or both totaled $6.4 to $8.1 billion, 5% of which was for patients with both HIV infection and tuberculosis., Conclusions: This is the first study to use a nationally representative sample of hospitals, combined with cost data, to estimate hospitalizations and their costs for HIV and tuberculosis care. Our findings suggest that the convergence of the HIV and tuberculosis epidemics has had an increasing effect on morbidity and the cost of care among young adults in the United States. The increasing prevalence of comorbidity of HIV infection and tuberculosis in inpatients underscores the need for strict infection control of tuberculosis on the part of hospitals, increased attention to prevention, and early identification and treatment of HIV infection, and tuberculosis to reduce morbidity, hospitalizations, and the cost of care.

Objective: To investigate potential transmission of Mycobacterium tuberculosis in aircraft from a crew member with tuberculosis., Design: Retrospective cohort study and survey., Setting: A large US airline carrier., Participants: A total of 212 crew members and 59 passengers who were exposed to a crew member with tuberculosis during a potentially infectious period (May through October 1992). Comparison volunteer sample of 247 unexposed crew members., Main Outcome Measures: Positive tuberculin skin test (TST) result or tuberculosis., Results: Rates of positive TST results were higher among foreign-born persons in all study groups. Among US-born comparisons and contacts, rates of positive TST results did not differ between comparisons and contacts exposed from May through July (5.3% vs 5.9%, respectively). However, contacts exposed from August through October had significantly higher rates of positive TST results than did contacts exposed from May through July (30% vs 5.8%, respectively; P < .001); two had documented TST conversions between September 1992 and February 1993. The risk of infection increased with increasing hours of exposure to the index case. Four (6.7%) of 59 frequent flyers were TST-positive; all flew in October., Conclusions: Data support the conclusion that M tuberculosis was transmitted from an infectious crew member to other crew members on an aircraft. Because of the clustering of TST-positive frequent flyers in October when the index patient was most infectious, transmission of M tuberculosis to passengers cannot be excluded.

Objective: To assess the joint use of purified protein derivative (PPD) and delayed-type hypersensitivity (DTH) antigens in screening individuals of unknown HIV serostatus for tuberculosis (TB) preventive therapy eligibility., Design: Population-based survey., Methods: A group of migrant farm workers were screened for HIV and skin-tested with PPD, tetanus toxoid (TET), Candida albicans (CAN) and mumps (MUM) antigens by the Mantoux method. Anergy was defined as a < or = 2 mm reaction to all four antigens. Eligibility for preventive therapy was defined as a reaction of > or = 5 mm to PPD among HIV-seropositive individuals, > or = 10 mm among HIV-seronegatives, or anergy., Results: A total of 253 out of 271 individuals had sufficient data for analysis. Of these, 15 (5%) were HIV-seropositive; 183 (75%), 175 (72%) and 157 (65%) reacted to TET, CAN, and MUM, respectively, and 113 (47%) were eligible for preventive therapy [108 (44%) PPD-positive, five (2%) anergic]. Use of PPD alone was 95% sensitive for detecting preventive therapy eligibility; PPD plus one DTH antigen was more sensitive (99%) but less specific (range, 69-85%); PPD plus two DTH antigens was most specific (CAN + MUM, 84%; TET + MUM, 93%; and TET + CAN, 100%)., Conclusions: In this population with 5% HIV seroprevalence, testing for anergy did not significantly increase the detection of preventive therapy eligibility. The use of two DTH antigens is very sensitive and specific. These results support the recommendation of joint PPD and anergy testing for the screening of HIV-seropositive individuals. Our data also suggest, however, that for individuals whose HIV serostatus is unknown, anergy testing should be considered as a screening tool only if the prevalence of anergy is expected to exceed the prevalence of PPD positivity.

This article updates the epidemiologic situation of HIV and AIDS infection and summarizes the most common clinical manifestations in Latin American countries. As of December 1992, a total of 59,723 AIDS cases had been reported to the Pan American Health Organization from Mexico, Central America, South America, and the Latin Caribbean. The number of deaths totaled 24,500, or 41% of the reported cases. HIV transmission patterns and clinical manifestations vary by region. The most common opportunistic illnesses in Latin America and their symptoms, including gastrointestinal, pulmonary, and dermatologic complications are discussed.

Objective: To determine the relative risk for human immunodeficiency virus (HIV-1) seroconversion in patients with and without genital ulcers caused by chancroid, syphilis, and herpes., Design: A prospective cohort study., Setting: An inner-city, sexually transmitted disease clinic., Patients: Patients seronegative for HIV-1 with and without genital ulcers who were followed for a minimum of 3 months., Interventions: Questionnaire to obtain data on demographics, sexual behavior, and illicit drug use; testing for HIV-1 at entry and at a minimum of 3 months after entry; medical examination for the presence or absence of genital ulcer disease., Results: Overall, 758 heterosexual men with no history of injection drug use completed the study; HIV-1 seroconversion occurred in 10 of 344 (2.9%; 95% CI, 1.4% to 5.3%) men with a genital ulcer and in 4 of 414 (1%; CI, 0.2% to 2.5%) without a genital ulcer (relative risk, 3.0; P = 0.05). In a multiple logistic regression analysis, those men with chancroid and a new sexually transmitted disease during follow-up each had about three times the risk for HIV-1 seroconversion (P < or = 0.04)., Conclusions: In this group of heterosexual men, chancroid and repeated acquisition of sexually transmitted diseases appeared to facilitate the sexual transmission of HIV-1.

To compare AIDS-defining conditions in women and men, US adult AIDS cases diagnosed between January 1988 and June 1991 and reported to the Centers for Disease Control and Prevention through June 1992 were examined. For most AIDS-defining conditions, the prevalence was similar for women and men when differences in race/ethnicity and mode of transmission were accounted for. Pneumocystis carinii pneumonia was the most prevalent condition (> 50%) regardless of gender, race/ethnicity, or mode of transmission. By logistic regression analysis, among injection drug users, conditions reported significantly more frequently in women than in men include esophageal candidiasis (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.40-1.62), herpes simplex virus (HSV) disease (OR, 1.68; CI, 1.46-1.94), and cytomegalovirus (CMV) disease (OR, 1.43; CI, 1.18-1.73). More knowledge of the interrelationships in women between HIV infection and secondary opportunistic infections, including candidiasis and sexually transmitted disease (e.g., HSV and CMV) is needed.

Objectives: In 1991 the incidence of acquired immunodeficiency syndrome (AIDS) in the United States was 31.6 per 100,000 population among Hispanics and 11.8 per 100,000 among non-Hispanic Whites. The purpose of this study was to further describe the AIDS epidemic among Hispanics by examining differences in risk factors among different Hispanic groups (as defined by birthplace)., Methods: AIDS cases reported to the Centers for Disease Control and Prevention from 1988 through 1991 were reviewed., Results: For men, except for those born in Puerto Rico, the predominant exposure category was male-male sex. The proportion of cases due to injection drug use was 35% among Hispanic men born in the United States, 27% among men born in the Dominican Republic, and 61% among men born in Puerto Rico, but < 10% among other Hispanic men and non-Hispanic White men. For women the predominant exposure category was injection drug use among Hispanics born in the United States (56%) and Puerto Rico (46%) and among non-Hispanic Whites (42%). The proportion of cases associated with injection drug use was significantly lower (< 30%) among other Hispanic women., Conclusions: AIDS prevention strategies must be geared toward different exposure categories among different Hispanic groups.

AIDS surveillance data reported to the Centers for Disease Control from January 1981 through December 1991 were analyzed in a study characterizing persons with human immunodeficiency virus (HIV) infection and extrapulmonary tuberculosis (EPTB) in the United States. Among 206,392 persons reported to have AIDS, 4,751 (2.3%) were also reported to have EPTB; of these cases, 4,257 (90%) were reported after September 1987, when the case definition for AIDS was revised to include EPTB. Seventy-six percent of persons in whom AIDS and EPTB were reported after this revision were born in the United States; among these persons, the annual percentage with EPTB in 1988-1991 ranged from 2.3% to 2.5%. The South and the Northeast accounted for 73% of EPTB cases in U.S.-born persons. U.S.-born non-Hispanic blacks (odds ratio [OR], 3.3) and U.S.-born Hispanics (OR, 2.1) were more likely than U.S.-born non-Hispanic whites to be reported as having EPTB. Intravenous drug users were at higher risk (OR, 2.9) than men who reported having had sex with other men. With the resurgence of tuberculosis and the continued expansion of the HIV epidemic, these data provide a useful basis for the targeting of efforts to control tuberculosis and to prevent HIV infection.

The Eighth International AIDS Symposium in Amsterdam, the Netherlands, provided updated scientific and programmatic information on the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) to thousands of interested participants. As in the other scientific areas, the amount of information presented in epidemiology and prevention was overwhelming; however, the scientific progress described was steady but incremental. This commentary summarizes progress made in three selected areas that were highlighted during the meeting's scientific session and a fourth that received widespread media attention: (1) the epidemiology of HIV/AIDS in heterosexual women; (2) tuberculosis as an increasing opportunistic pathogen in HIV-infected persons; (3) prevention research, practice, and policy; and (4) preliminary reports of severe immunodeficiency in persons without evident HIV infection. In order to stem HIV transmission worldwide, a safe and effective vaccine is urgently needed. Currently, in the absence of such a vaccine, it is crucial for all of the world's communities to apply the best science-based prevention methods available.

Background: Since 1990 several clusters of multidrug-resistant tuberculosis have been identified among hospitalized patients with the acquired immunodeficiency syndrome (AIDS). We investigated one such cluster in a voluntary hospital in New York., Methods: We compared exposures among 18 patients with AIDS in whom tuberculosis resistant to isoniazid and streptomycin was diagnosed from January 1989 through April 1990 (the case patients) with exposures among 30 control patients who had AIDS and tuberculosis susceptible to isoniazid, streptomycin, or both. We also compared exposures among the 14 case patients hospitalized during the six months before the diagnosis of tuberculosis (the exposure period) with those among 44 control patients with AIDS matched for duration of hospitalization. Mycobacterium tuberculosis isolates were typed with analysis of restriction-fragment-length polymorphism (RFLP)., Results: Case patients with drug-resistant tuberculosis were significantly more likely than controls with drug-susceptible tuberculosis to have been hospitalized during their exposure periods (14 of 18 vs. 10 of 30) (odds ratio, 7.0; 95 percent confidence interval, 1.6 to 36; P = 0.006). Case patients hospitalized during their exposure periods were significantly more likely to have been hospitalized on the same ward as a patient with infectious drug-resistant tuberculosis than were either controls with drug-susceptible tuberculosis hospitalized during their exposure periods or controls matched for duration of hospitalization (13 of 14 vs. 2 of 10 and 23 of 44) (odds ratio, 52; 95 percent confidence interval, 3.1 to 2474; P less than 0.001; and odds ratio, infinity; 95 percent confidence interval, 2.4 to infinity; P = 0.005, respectively). Among those hospitalized on the same ward, the rooms of case patients were closer to that of the nearest patient with infectious tuberculosis than were the rooms of controls matched for duration of hospitalization. M. tuberculosis isolates from 15 of 16 case patients had identical patterns on RFLP analysis. Of 16 patients' rooms tested with air-flow studies, only 1 had the recommended negative-pressure ventilation., Conclusions: Multidrug-resistant tuberculosis is readily transmitted among hospitalized patients with AIDS. Physicians must be alert to this danger and must enforce adherence to the measures recommended to prevent nosocomial transmission of tuberculosis.

Background: Since 1985, donors of organs or tissues for transplantation in the United States have been screened for human immunodeficiency virus type 1 (HIV-1), and more than 60,000 organs and 1 million tissues have been transplanted. We describe a case of transmission of HIV-1 by transplantation of organs and tissues procured between the time the donor became infected and the appearance of antibodies. The donor was a 22-year-old man who died 32 hours after a gunshot wound; he had no known risk factors for HIV-1 infection and was seronegative., Methods: We reviewed the processing and distribution of all the transplanted organs and tissues, reviewed the medical histories of the donor and HIV-1-infected recipients, tested stored donor lymphocytes for HIV-1 by viral culture and the polymerase chain reaction, and tested stored serum samples from four organ recipients for HIV-1 antigen and antibody., Results: HIV-1 was detected in cultured lymphocytes from the donor. Of 58 tissues and organs obtained from the donor, 52 could be accounted for by the hospitals that received them. Of the 48 identified recipients, 41 were tested for HIV-1 antibody. All four recipients of organs and all three recipients of unprocessed fresh-frozen bone were infected with HIV-1. However, 34 recipients of other tissues--2 receiving corneas, 3 receiving lyophilized soft tissue, 25 receiving ethanol-treated bone, 3 receiving dura mater treated with gamma radiation, and 1 receiving marrow-evacuated, fresh-frozen bone--tested negative for HIV-1 antibody. Despite immunosuppressive chemotherapy, HIV-1 antibody appeared between 26 and 54 days after transplantation in the three organ recipients who survived more than four weeks., Conclusions: Although rare, transmission of HIV-1 by seronegative organ and tissue donors can occur. Improvements in the methods used to screen donors for HIV-1, advances in techniques of virus inactivation, prompt reporting of HIV infection in recipients, and accurate accounting of distributed allografts would help to reduce further this already exceedingly low risk.

Prevalence of antibody to the human immunodeficiency virus type 1 (HIV-1) was assessed among 10,994 consecutive male and female entrants to 10 correctional systems in the United States. The HIV-1 seroprevalence for the 10 systems ranged from 2.1% to 7.6% for men and 2.5% to 14.7% for women; seroprevalence among women was higher than among men across nine of 10 systems. Using age 25 years to divide the population, HIV-1 prevalence among young women (5.2%) was significantly higher than among young men (2.3%), but similar to that in both older women (5.3%) and older men (5.6%). Overall, HIV-1 rates for nonwhites (4.8%) were higher than those for whites (2.5%). Although categories were identified across correctional systems, which may serve to focus prevention programs, variability in rates among correctional systems indicates that program planning must take local conditions into consideration.

By the end of 1989, 18,518 cases of Pneumocystis carinii infection and 5,614 cases of Toxoplasma gondii infection were reported to the Centers for Disease Control as the AIDS indicator disease. Pneumocystosis did not vary according to gender, race or risk factors; whereas toxoplasmosis was more common in black males with no known risk factors. Immigrants to the USA from Africa, Latin America and Haiti are three to four times more likely to develop toxoplasmic encephalitis than American-born patients with AIDS. The implications of this epidemiologic data for the predictive value of serology and clinical trials are discussed.

The transmission of tuberculosis is a recognized risk in health-care settings. Several recent outbreaks of tuberculosis in health-care settings, including outbreaks involving multidrug-resistant strains of Mycobacterium tuberculosis, have heightened concern about nosocomial transmission. In addition, increases in tuberculosis cases in many areas are related to the high risk of tuberculosis among persons infected with the human immunodeficiency virus (HIV). Transmission of tuberculosis to persons with HIV infection is of particular concern because they are at high risk of developing active tuberculosis if infected. Health-care workers should be particularly alert to the need for preventing tuberculosis transmission in settings in which persons with HIV infection receive care, especially settings in which cough-inducing procedures (e.g., sputum induction and aerosolized pentamidine [AP] treatments) are being performed. Transmission is most likely to occur from patients with unrecognized pulmonary or laryngeal tuberculosis who are not on effective antituberculosis therapy and have not been placed in tuberculosis (acid-fast bacilli [AFB]) isolation. Health-care facilities in which persons at high risk for tuberculosis work or receive care should periodically review their tuberculosis policies and procedures, and determine the actions necessary to minimize the risk of tuberculosis transmission in their particular settings. The prevention of tuberculosis transmission in health-care settings requires that all of the following basic approaches be used: a) prevention of the generation of infectious airborne particles (droplet nuclei) by early identification and treatment of persons with tuberculous infection and active tuberculosis, b) prevention of the spread of infectious droplet nuclei into the general air circulation by applying source-control methods, c) reduction of the number of infectious droplet nuclei in air contaminated with them, and d) surveillance of health-care-facility personnel for tuberculosis and tuberculous infection. Experience has shown that when inadequate attention is given to any of these approaches, the probability of tuberculosis transmission is increased. Specific actions to reduce the risk of tuberculosis transmission should include a) screening patients for active tuberculosis and tuberculous infection, b) providing rapid diagnostic services, c) prescribing appropriate curative and preventive therapy, d) maintaining physical measures to reduce microbial contamination of the air, e) providing isolation rooms for persons with, or suspected of having, infectious tuberculosis, f) screening health-care-facility personnel for tuberculous infection and tuberculosis, and g) promptly investigating and controlling outbreaks. Although completely eliminating the risk of tuberculosis transmission in all health-care settings may be impossible, adhering to these guidelines should minimize the risk to persons in these settings.

A population-based serosurvey of human immunodeficiency virus in Belle Glade, FL, enabled evaluation of risk factors for hepatitis B virus (HBV) infection in this racially mixed community. Serum samples from 725 adults and 130 children were tested for markers of HBV infection, and histories of exposure to HBV were obtained by interview. The overall prevalence of past or present HBV infection was 26%; prevalence was 9% among whites, 5% among Hispanics, 30% among blacks, and 57% among Haitians. Prevalence of HBV infection was 3% in children aged 2-10 years and increased to 31% in adults greater than 17 years. Of adults seropositive for HBV, only 5% had homosexual partners or used parenteral drugs, but 47% had a positive serologic test for syphilis. Factors associated with HBV infection in adults were positive serologic test for syphilis (odd ratio [OR] = 3.1; 95% confidence limits [CL] = 2.0, 4.8), and having had two or more lifetime heterosexual partners (OR = 3.2; 95% CL = 1.6, 6.4). In this community, HBV infection was transmitted predominantly by heterosexual contact.

From 1 June 1981 through 31 January 1984, 201 cases of the acquired immunodeficiency syndrome were reported involving persons who could not be classified into a group identified to be at increased risk for this syndrome. Thirty-five had received transfusions of single-donor blood components in the 5 years preceding diagnosis of the syndrome and 30 were sexual partners of persons belonging to a high-risk group. Information was incomplete for most remaining patients, but because many of these patients were demographically similar to populations recognized to be at increased risk for the syndrome, previously identified risk factors may have been present but not reported for some of them. Additionally, a few persons who met the case definition for the syndrome probably had other reasons for their opportunistic disease and did not have the acquired immunodeficiency syndrome. The slow emergence of the acquired immunodeficiency syndrome in new populations is consistent with transmission mediated through sexual contact or parenteral exposure to blood.

Maguari virus, a member of the Bunyamwera serogroup (family Bunyaviridae, genus Bunyavirus) has not been isolated north of Trinidad. Anecdotal information from other investigators has indicated the presence of antibody to Maguari virus in human residents of south Florida. We attributed such antibody to either cross-reactivity with Tensaw virus, the only Bunyamwera serogroup virus known in south Florida, or to cross-reactivity to an antigenic subtype or variant of Tensaw virus. Five strains, identified as Tensaw virus when they were isolated from mosquitoes collected in south Florida more than 20 years ago, were retrieved from storage. They were compared by serum dilution-plaque reduction neutralization tests with Bunyamwera serogroup prototypes Tensaw, Maguari, Cache Valley, and Tlacotalpan viruses. The south Florida isolates were shown to be most closely related to prototype Tensaw virus and most distantly related to prototype Maguari virus. One isolate could not be distinguished from prototype Tensaw virus, and the other 4 appeared to be subtypes of prototype Tensaw virus. More than 300 serum samples from humans in south Florida were tested for neutralizing antibody to prototypes Tensaw and Maguari viruses and to 3 of the field isolates. Thirteen had antibody to prototype Tensaw virus only, 19 to prototype Maguari virus only, and 39 to both. Antibody to all but 6 of these 71 was attributed to infection with Tensaw virus, to a subtype of Tensaw virus, or to travel or birth outside the United States. It is likely that those with antibody to Maguari virus only had been infected with yet another subtype of Tensaw virus, although another, undiscovered, Bunyamwera serogroup virus may exist in south Florida.

Information obtained for all persons with the acquired immunodeficiency syndrome (AIDS) reported to the Centers for Disease Control, Atlanta, includes a question about employment in a health care or clinical laboratory setting. As of May 1, 1986, a total of 922 (5.5%) of 16,748 adults with AIDS reported employment in such settings. Ninety-five percent of these health care workers belonged to recognized high-risk groups for AIDS; the proportion with "no identified risk" has not increased with time. All AIDS patients (including health care workers) who do not belong to high-risk groups are referred for further investigation. Of 88 health care workers initially reported with no identified risk, ten were from countries where heterosexual transmission is believed to play a major role; additional information was unobtainable or incomplete for 17 individuals. Of 61 persons on whom interviews or other follow-up information was obtained, 44 (73%) were reclassified. Specific occupational exposures that could be implicated as the source of human immunodeficiency virus infection were not identified for any health care workers with AIDS. A review of surveillance data supports other studies indicating that the risk of human immunodeficiency virus transmission in the occupational setting is low.

The acquired immunodeficiency syndromE (AIDS) is a very serious illness caused by a human T-lymphotropic retrovirus: human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). It primarily affects young adults living in one of several major metropolitan areas. Most patients are homosexual men, but heterosexual men and women have also been affected. Heterosexual men and women who use intravenous drugs, who are hemophiliacs, or who are sex partners of AIDS patients appear to be at increased risk for developing the disease.

To extend previous work showing that the risk of AIDS (acquired immunodeficiency syndrome) is higher in US Hispanics than in Whites who are not Hispanic, we compared US residents born in different Latin American countries. We computed the cumulative incidence (CI) of AIDS and the distribution of cases by mode of exposure. Cases were those reported to the Centers for Disease Control between June 1, 1981 and December 12, 1988, and populations specific for birthplace were from the 1980 census. The reference group was the White population that was not Hispanic, CI 25.7/100,000. We estimated a similar rate in Mexican-born persons (25.3/100,000). In the South and West, the rate in Mexican-born Hispanics was half the reference rate. In each US region, the CI of AIDS in heterosexual intravenous drug abusers (IVDAs) in Puerto Rican-born persons was several times greater than that in other Latin American-born persons. Puerto Rican-born persons were the only Latin American-born persons in whom most cases were in heterosexual IVDAs. The data suggest that resources for preventing AIDS in Hispanics are needed most in those of Puerto Rican ethnicity for AIDS related to intravenous drug abuse.

Through Sept 30, 1987, two thousand fifty-nine patients with acquired immunodeficiency syndrome (AIDS) and no recognized risk factors were reported to the Centers for Disease Control. Risk history was incomplete or unobtainable for 921 (45%) of them. Risk factors were ultimately identified for 825 (72%) of the remaining 1138. Another 32 persons (3%) did not meet the case definition for AIDS. Risk factors could not be identified for the remaining 281 patients (25%), despite additional information. Of these, 178 (63%) were interviewed with standard questionnaires; 38% reported sexually transmitted diseases and 34% of the men reported sexual contact with prostitutes. There was no evidence for new transmission modes. Although the proportion of AIDS patients with undetermined risk factors has increased significantly during the past year, the adjusted proportion shows no significant change over time. Thus, follow-up of AIDS patients with no apparent risk factors suggests that modes of transmission for human immunodeficiency virus have remained stable.

We analyzed the variation in the risk of AIDS in US Blacks, Hispanics, and other racial/ethnic groups relative to that in Whites (non-Hispanic) by geographic area and mode of acquiring HIV infection, based on data reported between June 1, 1981 and January 18, 1988 to the Centers for Disease Control and 1980 US census data. Relative risks (RRs) in Blacks and Hispanics were highest in the northeast region, and higher in suburbs than in central cities of metropolitan areas. RRs in Blacks and Hispanics were greatest for AIDS directly or indirectly associated with intravenous-drug abuse by heterosexuals (range: 5.7-26.9) and were also high for AIDS associated with male bisexuality (range: 2.5-4.8), suggesting that these behaviors may be more prevalent in Blacks and Hispanics than in Whites. Prevention strategies should take into account these racial/ethnic differences.

The high cumulative incidence of AIDS and the large percentage of AIDS patients with no identified risks in Belle Glade, Florida, were evaluated through case interviews and neighborhood-based seroepidemiologic studies. It was found that of 93 AIDS patients reported between July 1982 and 1 August 1987, 34 could be directly linked to at least one other AIDS patient or to a person with AIDS-related complex by sexual contact, sharing of needles during intravenous drug abuse (or both), or perinatal exposure; of 877 randomly selected adults, 28 had antibodies to HIV; no person over age 60 and none of 138 children aged 2 to 10 years had antibodies to HIV; no clustering of infected persons within households occurred, except in sex partners; and HIV-seropositive adults were more likely than HIV-seronegative adults to be from Haiti, have a lower income, report sex with intravenous drug abusers, and have a history of previous treatment for sexually transmitted diseases. The presence of antibodies to five arboviruses prevalent in South Florida or the Caribbean did not correlate significantly with HIV infection. The high cumulative rate of AIDS in Belle Glade appears to be the result of HIV transmission through sexual contact and intravenous drug abuse; the evidence does not suggest transmission of HIV through insects.

Screening of blood product donations for antibody to HIV began in Mexico in May 1986. From June to October 1986, the HIV cumulative seroprevalence increased from 6.3 to 9.2% in a commercial plasma collection center. Of the 281 people who donated the antibody-positive units, 62 (22.1%) had documented seroconversion during these 5 months. An epidemiologic study of 54 seropositive and 58 seronegative donors was carried out. The HIV serologic status did not change in any of these donors after repeat testing. Only 13.0% of the seropositives and 15.5% of the seronegatives had any of the known risk factors for AIDS. There was a direct relationship between frequency of plasma donation and the risk of being seropositive. A survey of employees disclosed the frequent re-use of disposable blood collection equipment. We conclude that HIV transmission had probably occurred in this plasma collection center.