Epidemiology of HIV infection and AIDS in the United States

By the end of 1987, nearly 50,000 cases of acquired immunodeficiency syndrome (AIDS) had been reported since 1981, 20,745 in the past year alone. Black and Hispanic adults and children have reported rates 3 to 12 times as high as whites. This can be largely attributed to higher reported rates in black and Hispanic intravenous (IV) drug abusers, their sex partners, and infants. In 1986, reported AIDS deaths increased adult male and female mortality in the United States by an estimated 0.7 and 0.07%, respectively, with much greater increases in selected age groups or areas of the country. The greatest variation in infection with the human immunodeficiency virus (HIV) (0 to 70%) has been found in surveys of IV drug abusers, while surveys of homosexual men reveal infection rates of 20 to 50%. Infection with HIV ranged from 0 to 2.6% in limited sexually transmitted disease clinic surveys of heterosexual men and women without a history of IV drug abuse or known sexual contact with persons at increased risk. The modes of HIV transmission are now well understood, but a large amount of biologic variability in efficiency of transmission remains to be explained. The period between initial infection with HIV and the development of AIDS is variable, but the risk for disease progression increases with duration of infection.     

Seroprevalence and epidemiological correlates of HTLV-I infection in U.S. blood donors

Screening for human T-lymphotropic virus type I (HTLV-I) antibodies was performed on sera from 39,898 blood donors at eight blood centers in geographically distinct areas of the United States. Ten donors (0.025 percent) showed evidence of HTLV-I seropositivity by enzyme immunoassays; this was confirmed by protein immunoblot and radioimmunoprecipitation. Seroprevalence rates ranged from 0 to 0.10 percent at the locations sampled, with HTLV-I antibodies found predominantly in donors from the southeastern and southwestern United States. Matched case-control interviews and laboratory studies were performed on five seropositive women and two seropositive men who participated in an identity-linked collection of sera from a subset of 33,893 donors at six of the eight blood centers. Four of the women and both men are black; one woman is Caucasian. Four of the seven seropositive individuals admitted to prior intravenous drug abuse or sexual contact with an intravenous drug user. Sexual contact with native inhabitants of an HTLV-I endemic area was the only identified risk factor for one male. The distribution of HTLV-I antibodies in this U.S. blood donor sample corroborates the previously reported epidemiology of this agent and suggests that additional donor screening measures, including the testing of donated blood for HTLV-I markers, may be necessary to prevent the spread of HTLV-I to transfusion recipients.     

The epidemiology of AIDS: current status and future prospects

The reported incidence of acquired immune deficiency syndrome (AIDS) continues to increase in countries throughout the world. On the basis of a polynomial model for extrapolation, the cumulative number of cases diagnosed and reported since 1981 in the United States is expected to double during the next year with over 12,000 additional cases projected to be diagnosed by July 1986. The annual incidence rates for single (never-married) men in Manhattan and San Francisco, intravenous drug users in New York City and New Jersey, and persons with hemophilia A ranged from 261 to 350 per 100,000 population during 1984. For single men aged 25 to 44 years in Manhattan and San Francisco, AIDS was the leading cause of premature mortality in 1984 as measured by years of potential life lost. Infection with HTLV-III/LAV is considerably more common than reported AIDS in high-risk populations and can persist at least for several years, so the presence of specific antibody should be considered presumptive evidence of current infection. The screening of donated blood and plasma for antibody to HTLV-III/LAV and use of safer clotting factor concentrates should greatly reduce HTLV-III/LAV transmission through blood and blood products. Most HTLV-III/LAV infections occur through sexual transmission, use of contaminated needles, and as a result of infected mothers passing the virus to newborns. Continued research commitment is needed to develop an HTLV-III/LAV vaccine and therapy for this infection. In the interim, widespread community efforts are needed to minimize transmission.     

AIDS in Africa: an epidemiologic paradigm

Cases of the acquired immune deficiency syndrome (AIDS) have been reported in countries throughout the world. Initial surveillance studies in Central Africa suggest an annual incidence of AIDS of 550 to 1000 cases per million adults. The male to female ratio of cases is 1:1, with age- and sex-specific rates greater in females less than 30 years of age and greater in males over age 40. Clinically, AIDS in Africans is often characterized by a diarrhea-wasting syndrome, opportunistic infections, such as tuberculosis, cryptococcosis, and cryptosporidiosis, or disseminated Kaposi's sarcoma. From 1 to 18% of healthy blood donors and pregnant women and as many as 27 to 88% of female prostitutes have antibodies to human immunodeficiency virus (HIV). The present annual incidence of infection is approximately 0.75% among the general population of Central and East Africa. The disease is transmitted predominantly by heterosexual activity, parenteral exposure to blood transfusions and unsterilized needles, and perinatally from infected mothers to their newborns, and will continue to spread rapidly where economic and cultural factors favor these modes of transmission. Prevention and control of HIV infection through educational programs and blood bank screening should be an immediate public health priority for all African countries.     

A larger spectrum of severe HIV-1--related disease in intravenous drug users in New York City

Increasing mortality in intravenous (IV) drug users not reported to surveillance as acquired immunodeficiency syndrome (AIDS) has occurred in New York City coincident with the AIDS epidemic. From 1981 to 1986, narcotics-related deaths increased on average 32% per year from 492 in 1981 to 1996 in 1986. This increase included deaths from AIDS increasing from 0 to 905 and deaths from other causes, many of which were infectious diseases, increasing from 492 to 1091. Investigations of these deaths suggest a causal association with human immunodeficiency virus (HIV) infection. These deaths may represent a spectrum of HIV-related disease that has not been identified through AIDS surveillance and has resulted in a large underestimation of the impact of AIDS on IV drug users and blacks and Hispanics.     

Prevalence and patterns of same-gender sexual contact among men

The prevalence and patterns of same-gender sexual contact among men are key components of models of the spread of HIV infection and AIDS in the U.S. population. Previous estimates by Kinsey et al. from data collected between 1938 and 1948 have been widely criticized for inadequacies of sample design. New lower-bound estimates of prevalence developed from data from a national sample survey conducted in 1970 indicate that minimums of 20.3 percent of adult men in the United States in 1970 had sexual contact to orgasm with another man at some time in life; 6.7 percent had such contact after age 19; and between 1.6 and 2.0 percent had such contact within the previous year. Although these estimates incorporate adjustments for missing data, the likelihood of underreporting suggests that these estimates might be lower bounds on the prevalence of same-gender sex among men. Two sets of alternative estimates are derived to assess the sensitivity of these estimates to the assumptions made in imputing values to missing data. Detailed estimates are presented by frequency of contact, age, education, and marital status; and supporting estimates are derived from a 1988 national survey. Data from both the 1970 and 1988 surveys indicate that never-married men are more likely than other men to have had same-gender sexual contacts within the last year. The 1970 survey also indicates, however, that approximately half the men estimated to have such contacts are found among the more numerous population of currently or previously married men.     

Antibodies to cell membrane antigens associated with human T-cell leukemia virus in patients with AIDS

The acquired immune deficiency syndrome (AIDS), which has recently occurred at increasing rates in homosexual men, intravenous drug users, and others, is characterized by the development of Kaposi's sarcoma and several opportunistic infections including pneumonia caused by Pneumocystis carinii. Serum samples from patients with AIDS and from matched and unmatched control subjects were examined for the presence of antibodies to cell membrane antigens associated with human T-cell leukemia virus. Nineteen of 75 of the AIDS patients had antibodies directed to surface antigens of Hut 102, a reference T lymphoid cell line infected with leukemia virus, as did two of the 336 control subjects.     

Infectious diseases. China awakens to fight projected AIDS crisis

Official tallies count only 670 confirmed AIDS cases and 18,143 confirmed HIV-infected people among China's 1.2 billion population. Now changing social mores, including an increase in drug use and a boom in commercial sex, combined with a tainted blood supply, have led China to the brink of an AIDS explosion. But its historic isolation also gives the country an advantage in testing the latest vaccines, as the different strains of HIV have not yet commingled there; China's well-developed public health infrastructure could also help facilitate clinical trials.     

Population-level HIV declines and behavioral risk avoidance in Uganda

Uganda provides the clearest example that human immunodeficiency virus (HIV) is preventable if populations are mobilized to avoid risk. Despite limited resources, Uganda has shown a 70% decline in HIV prevalence since the early 1990s, linked to a 60% reduction in casual sex. The response in Uganda appears to be distinctively associated with communication about acquired immunodeficiency syndrome (AIDS) through social networks. Despite substantial condom use and promotion of biomedical approaches, other African countries have shown neither similar behavioral responses nor HIV prevalence declines of the same scale. The Ugandan success is equivalent to a vaccine of 80% effectiveness. Its replication will require changes in global HIV/AIDS intervention policies and their evaluation.     

Sexual deprivation increases ethanol intake in Drosophila

The brain's reward systems reinforce behaviors required for species survival, including sex, food consumption, and social interaction. Drugs of abuse co-opt these neural pathways, which can lead to addiction. Here, we used Drosophila melanogaster to investigate the relationship between natural and drug rewards. In males, mating increased, whereas sexual deprivation reduced, neuropeptide F (NPF) levels. Activation or inhibition of the NPF system in turn reduced or enhanced ethanol preference. These results thus link sexual experience, NPF system activity, and ethanol consumption. Artificial activation of NPF neurons was in itself rewarding and precluded the ability of ethanol to act as a reward. We propose that activity of the NPF-NPF receptor axis represents the state of the fly reward system and modifies behavior accordingly.     

A tale of two futures: HIV and antiretroviral therapy in San Francisco

The effect of antiretroviral therapy (ART) in preventing human immunodeficiency virus (HIV) infections and averting acquired immunodeficiency syndrome (AIDS) deaths in the San Francisco gay community over the next 10 years was predicted. A transmission model was coupled with a statistical approach that enabled inclusion of a high degree of uncertainty in the potential treatment effects of ART (in terms of infectivity and survival), increase in risky behavior, and rate of emergence of drug resistance. Increasing the usage of ART in San Francisco would decrease the AIDS death rate and could substantially reduce the incidence rate.     

AIDS: an international perspective

The acquired immunodeficiency syndrome (AIDS) and infection with the human immunodeficiency virus type 1 (HIV-1) constitute a worldwide public health problem. Whereas in Europe and in most of the Americas transmission of HIV-1 has occurred predominantly among homosexual men and intravenous drug abusers, in Africa a distinct epidemiologic pattern has emerged that indicates that HIV-1 infection is mainly heterosexually acquired. Heterosexual transmission appears to be increasing in some parts of Latin America and the Caribbean, and possibly in the United States. In addition to HIV-1, at least one other human retrovirus, namely HIV-2, has been implicated as a cause of AIDS in Africa and Europe. Factors that influence heterosexual transmission of HIV-1 include genital ulcerations, early or late stages of HIV-1 infection in the index case, and possibly oral contraception and immune activation. The rate of perinatal transmission is enhanced when the mother's illness is more advanced. AIDS and HIV-1 infection may have a significant impact not only on public health, but also on the demography and socioeconomic conditions of some developing countries. Programs for the prevention and control of AIDS should be an immediate priority in all countries.     

HIV decline associated with behavior change in eastern Zimbabwe

Few sub-Saharan African countries have witnessed declines in HIV prevalence, and only Uganda has compelling evidence for a decline founded on sexual behavior change. We report a decline in HIV prevalence in eastern Zimbabwe between 1998 and 2003 associated with sexual behavior change in four distinct socioeconomic strata. HIV prevalence fell most steeply at young ages-by 23 and 49%, respectively, among men aged 17 to 29 years and women aged 15 to 24 years-and in more educated groups. Sexually experienced men and women reported reductions in casual sex of 49 and 22%, respectively, whereas recent cohorts reported delayed sexual debut. Selective AIDS-induced mortality contributed to the decline in HIV prevalence.     

Reconstruction and future trends of the AIDS epidemic in the United States

There has been considerable uncertainty in estimates of past and current human immunodeficiency virus (HIV) infection rates in the United States. Statistical estimates of historical infection rates can be obtained from acquired immunodeficiency syndrome (AIDS) incidence data and the incubation period. However, this approach is subject to a number of sources of uncertainty and two other approaches, epidemic models of HIV transmission and surveys of HIV prevalence, are used to corroborate and refine the statistical estimates. Analyses suggest the HIV infection rate in the United States grew rapidly in the early 1980s, peaked in the mid-1980s, and subsequently declined markedly. Due both to the decline in the underlying infection rate and to the development of effective therapies that may delay AIDS diagnosis, overall AIDS incidence may plateau during the next 5 years. However, the number of individuals with advanced HIV disease without a diagnosis of AIDS who could potentially benefit from therapy is expected to increase 40% by 1995 as infected individuals progress to more advanced stages of HIV disease. Thus, although the overall HIV infection rate has declined, the demands on the U.S. health care system for treatment and care of HIV-infected individuals remain enormous.     

Preventing AIDS but not HIV-1 infection with a DNA vaccine

Although there has been some success in treating human immunodeficiency virus (HIV) patients with triple drug therapy (highly active antiretroviral therapy or HAART), the best hope for combating AIDS (the disease caused by HIV) could be a combination of drug therapy and vaccination, according to Shen and Siliciano in their Perspective. A new study in rhesus monkeys treated with a DNA vaccine (Barouch et al.) demonstrates that a powerful vaccine-induced CD8(+) cytolytic T cell response reduces the amount of virus in the blood to very low levels preventing the drastic decrease in CD4(+) T helper cells and subsequent immunodeficiency. As the Perspective authors explain, vaccinating HIV patients that are receiving HAART may enable HIV levels to be permanently brought under control such that the drug treatment can eventually be stopped.     

Origins of HIV and the evolution of resistance to AIDS

The cross-species transmission of lentiviruses from African primates to humans has selected viral adaptations which have subsequently facilitated human-to-human transmission. HIV adapts not only by positive selection through mutation but also by recombination of segments of its genome in individuals who become multiply infected. Naturally infected nonhuman primates are relatively resistant to AIDS-like disease despite high plasma viral loads and sustained viral evolution. Further understanding of host resistance factors and the mechanisms of disease in natural primate hosts may provide insight into unexplored therapeutic avenues for the prevention of AIDS.     

Synthetic peptide immunoassay distinguishes HIV type 1 and HIV type 2 infections

Efforts to solve the epidemiologic puzzle of AIDS in Africa are complicated by the presence of multiple human retroviruses. Simple serologic tests that unambiguously distinguish among infections by these retroviruses are essential. To that end, a partially conserved immunoreactive epitope was identified in the transmembrane glycoproteins of human immunodeficiency viruses (HIV) types 1 and 2. Synthetic peptides derived from these conserved domains were used in sensitive and specific immunoassays that detect antibodies in sera from patients infected with HIV-1 or HIV-2. By making single amino acid substitutions in the HIV-1 peptide, it was possible to demonstrate HIV-1 strain-specific antibody responses to this epitope. Such custom-designed peptides synthesized from this domain are likely to detect newly discovered HIV types, define infection with specific HIV strains, and allow detection of group-common antibodies.     

Naturally acquired antibodies to sporozoites do not prevent malaria: vaccine development implications

The first human vaccines against the malaria parasite have been designed to elicit antibodies to the circumsporozoite protein of Plasmodium falciparum. However, it is not known whether any level of naturally acquired antibodies to the circumsporozoite protein can predict resistance to Plasmodium falciparum malaria. In this study, 83 adults in a malaria-endemic region of Kenya were tested for circumsporozoite antibodies and then treated for malaria. They were monitored for the development of new malaria infections for 98 days. Antibody levels, as determined by four assays in vitro, were indistinguishable between the 60 individuals who did and the 23 who did not develop parasitemia during follow-up, and there was no apparent relation between day of onset of parasitemia and level of antibodies to circumsporozoite protein. Unless immunization with sporozoite vaccines induces antibodies that are quantitatively or qualitatively superior to the circumsporozoite antibodies in these adults, it is unlikely that such antibodies will prevent infection in areas with as intense malaria transmission as western Kenya.     

AIDS. Origins of HIV

Establishing the date when immunodeficiency viruses were transmitted from nonhuman primates to humans should provide a clue to the origin of the AIDS pandemic. In his Perspective, Hillis discusses an important analysis of the molecular divergence of SIV and HIV genes (Korber et al.). This analysis establishes 1931 as the date of origin of the HIV-1 M-group viruses (the principal cause of the AIDS pandemic). Hillis discusses three possible hypotheses of immunodeficiency virus transmission that are consistent with this date.     

昆虫性信息素生物学研究与应用进展

近年来,利用昆虫本身生理生化特性和行为学特点作为害虫防治的新技术日益受到重视,其中性信息素的研究尤为突出。性信息素是昆虫交配时两性相互寻找过程中的重要纽带和必备因素,可以保证昆虫在种群内雌雄个体之间性的联系及物种有条不紊的繁衍。昆虫性信息素具有专一、高效、无毒、无污染、不伤益虫等优点。就近些年来的昆虫性信息素生物学特性及应用的情况进行了较为详细的概述,并对其进行了展望。