A population-based study of the prevalence and risk factors of low-grade Plasmodium falciparum malaria infection in children aged 0-15 years old in northern Tanzania.

OBJECTIVES: Northern Tanzania experiences significant malaria-related morbidity and mortality, but accurate data are scarce. We update the data on patterns of low-grade Plasmodium falciparum malaria infection among children in northern Tanzania. METHODS: Plasmodium falciparum malaria prevalence (pfPR) was assessed in a representative sample of 819 children enrolled in 94 villages in northern Tanzania between October 2015 and August 2016, using a complex survey design. Individual- and household-level risk factors for pfPR were elicited using structured questionnaires. pfPR was assessed using rapid diagnostic tests (RDTs) and thick film microscopy (TFM). Associations with pfPR, based on RDT, were assessed using adjusted odds ratios (aOR) and confidence intervals (CI) from weighted survey logistic regression models. RESULTS: Plasmodium falciparum malaria prevalence (pfPR) was 39.5% (95% CI: 31.5, 47.5) by RDT and 33.4% (26.0, 40.6) by TFM. pfPR by RDT was inversely associated with higher-education parents, especially mothers (5-7 years of education: aOR 0.55; 95% CI: 0.31, 0.96, senior secondary education: aOR 0.10; 95% CI: 0.02, 0.55), living in a house near the main road (aOR 0.34; 95% CI: 0.15, 0.76), in a larger household (two rooms: aOR 0.40; 95% CI: 0.21, 0.79, more than two rooms OR 0.35; 95% CI: 0.20, 0.62). Keeping a dog near or inside the house was positively associated with pfPR (aOR 2.01; 95% CI: 1.26, 3.21). pfPR was not associated with bed-net use or indoor residual spraying. CONCLUSIONS: Nearly 40% of children in northern Tanzania had low-grade malaria antigenaemia. Higher parental education and household metrics but not mosquito bed-net use were inversely associated with pfPR.

OBJECTIFS: La Tanzanie connaît une morbidité et une mortalité importantes liées au paludisme, mais les données précises sont rares. Nous mettons à jour les données sur les profils en matière d'infection par le paludisme à Plasmodium falciparum de faible grade chez les enfants dans le nord de la Tanzanie. MÉTHODES: La prévalence du paludisme à P. falciparum (pfPR) a été évaluée sur un échantillon représentatif de 819 enfants inscrits dans 94 villages dans le nord de la Tanzanie entre octobre 2015 et août 2016, à l'aide d'un plan d'enquête complexe. Des facteurs de risque de pfPR au niveau individuel et au niveau du ménage ont été déterminés à l'aide de questionnaires structurés. La pfPR a été évaluée à l'aide de tests de diagnostic rapides (TDR) et de microscopie à film épais (TFM). Les associations avec la pfPR, sur la base des TDR, ont été évaluées à l'aide des rapports de cotes ajustés (aOR) et des intervalles de confiance (IC) de modèles de régression logistique de surveillances pondérées. RÉSULTATS: La pfPR était de 39,5% (IC95%: 31,5-47,5) avec les TDR et de 33,4% (26,0-40,6) avec la TFM. La pfPR par les TDR était inversement associée aux parents avec un niveau d'éducation plus élevé, en particulier les mères (5-7 ans d'études: aOR: 0,55; IC95%: 0,31-0,96, enseignement secondaire supérieur: aOR: 0,10; IC95%: 0,02-0,55), vivre dans une maison proche de la route principale (aOR: 0,34; IC95%: 0,15-0,76), dans un ménage plus grand (2 chambres: aOR: 0,40; IC95%: 0,21-0,79, plus de 2 pièces aOR: 0,35; IC95%: 0,20-0,62). Garder un chien près ou à l'intérieur de la maison était positivement associé à la pfPR (aOR: 2,01; IC95%: 1,26-3,21). La pfPR n'était pas associée à l'utilisation de moustiquaire ou à la pulvérisation de résidus à l'intérieur. CONCLUSIONS: Près de 40% des enfants dans nord de la Tanzanie présentaient une antigénémie paludéenne de faible grade. Un niveau d'éducation parentale plus élevé et les indicateurs du ménage, mais pas l'utilisation de moustiquaires, étaient inversement associés à la pfPR.

National cohort study of reproductive risk factors for rheumatoid arthritis in Denmark: a role for hyperemesis, gestational hypertension and pre-eclampsia?

OBJECTIVES: While reproductive factors might plausibly be involved in the aetiology of rheumatoid arthritis (RA), the female predominance remains unexplained. A study was undertaken to address the possible impact of live births, pregnancy losses and pregnancy complications on the subsequent risk of RA in a nationwide cohort study. METHODS: National register data were used to link reproductive histories and later RA hospitalisations in a cohort of 4.4 million Danes. As a measure of relative risk associated with different reproductive histories, ratios of first inpatient RA hospitalisation rates (RRs) were used with 95% confidence intervals (CIs) obtained by Poisson regression analysis. RESULTS: Overall, 7017 women and 3041 men were admitted to hospital with RA in 1977-2004 (88.8 million person-years). The risk of RA was inversely associated with age at birth of first child in both women and men (p for trend <0.001). Overall, nulliparity and a history of pregnancy loss were not associated with RA risk but, compared with one-child mothers, women with two (RR 0.84; 95% CI 0.78 to 0.90) or three (RR 0.83; 95% CI 0.77 to 0.91) children were at reduced risk. The risk of RA was increased in women with a history of hyperemesis (RR 1.70; 95% CI 1.06 to 2.54), gestational hypertension (RR 1.49; 95% CI 1.06 to 2.02) or pre-eclampsia (RR 1.42; 95% CI 1.08 to 1.84). CONCLUSIONS: One-child mothers and young parents are at increased risk of RA later in life, possibly due to socioeconomic factors. The novel finding of a significantly increased risk of RA in women whose pregnancies were complicated by hyperemesis, gestational hypertension or pre-eclampsia might reflect reduced immune adaptability to pregnancy in women disposed to RA or a role of fetal microchimerism in the aetiology of RA.

Solid tumors after chronic lymphocytic leukemia.

Prior reports indicate that patients with chronic lymphocytic leukemia (CLL) may be at increased risk of subsequent neoplasms. This study quantified the risk of second cancers among 16 367 patients with CLL in the population-based Surveillance, Epidemiology and End Results Program. Overall, the observed/expected ratio (O/E) was 1.20 (95% confidence interval [CI], 1.15-1.26). Second cancer risks for patients who received chemotherapy only as the first course of treatment (O/E = 1.21) were similar to risks for those who received no treatment initially (O/E = 1.19). Significant excesses were found for Kaposi sarcoma (O/E = 5.09), malignant melanoma (O/E = 3.18), and cancers of the larynx (O/E = 1.72) and the lung (O/E = 1.66). Increased risks were also found for brain cancer among men (O/E =1.91) and for cancers of the stomach (O/E = 1.76) and bladder (O/E = 1.52) among women. Additional investigations of cancers after CLL are needed to explore the role of immunologic impairment and/or other etiologic influences.

Appendectomy and subsequent risk of inflammatory bowel diseases.

BACKGROUND: Case-control studies have reported an inverse relationship between appendectomy and the risk of ulcerative colitis, but the association has not been confirmed in prospective studies. METHODS: Using national hospital discharge registry data in Denmark, the authors followed up 154,434 patients who underwent appendectomy during the period 1977 to 1989 to investigate whether they had subsequent hospitalizations for ulcerative colitis and Crohn's disease. Ratios of observed-to-expected first hospitalizations for inflammatory bowel diseases served as measures of the relative risk (RR). RESULTS: Hospitalization for ulcerative colitis occurred in 84 patients who had appendectomies versus 97.0 expected (RR = 0.87; 95% CI, 0.69-1.07). RRs were not significantly reduced in subgroups defined by sex, age, time since appendectomy, calendar period, or cause of appendectomy. Hospitalization for Crohn's disease occurred in excess (RR = 2.88; 95% CI, 2.45-3.39; n = 150), notably in the first year after appendectomy (RR = 10.83; 95% CI, 8.49-13.62; n = 73); but after 5 years, the RR was not significantly elevated. CONCLUSIONS: This large population-based cohort study failed to support a significant inverse association between appendectomy and ulcerative colitis risk in the first decade after the operation. The excess of Crohn's disease shortly after appendectomy most likely reflects differential diagnostic problems in patients newly presenting with abdominal pain.

Trends in human immunodeficiency virus type 1 (HIV-1) load among HIV-1-infected children with hemophilia.

In human immunodeficiency virus type 1 (HIV-1)-infected persons, virus load (serum/plasma level of HIV) predicts outcome. Virus load trends have been characterized in adults and infants but not in children. Virus load trends in 22 male children with hemophilia who acquired HIV-1 postnatally (age 0.7-5.2 years at seroconversion) were studied. The mean HIV-1 load 2 years after seroconversion was 4.40 log10 copies/mL, and the mean change over time (slope) was 0.03 log10 copies/(mL x year). Significant among-children variation was apparent: a random effects model predicted that 95% of children had early virus loads 3.75-5.04 log10 copies/mL and slopes -0.07 to 0.12 log10 copies/(mL x year). Higher early virus loads and higher slopes were each associated with increased mortality (P=.006 and P=.03, respectively). In conclusion, those subjects had virus load trends similar to those in adults. Early virus loads were lower than those in vertically infected infants, which suggests that factors changing soon after birth affect viral replication.

Viral levels in newborn African infants undergoing primary HIV-1 infection.

We examined weekly changes in viral levels in seven untreated infants infected with HIV at birth. Viral levels spiked immediately but reverted quickly to plateau levels typical of infant HIV infection within 2 weeks of first detected viraemia. We speculated that the depletion of naive, susceptible cells is responsible for the rapid decrease in spike levels and that the rapid replacement of lymphocytes in infants causes the high plateau viral levels (10(5) copies/ml) to be sustained.

AIDS-related cancers in the era of highly active antiretroviral therapy.

Highly active antiretroviral therapy (HAART) has shown great efficacy in reducing human immunodeficiency virus levels, increasing immunity, and prolonging the survival of persons with acquired immunodeficiency syndrome (AIDS). The risk of life-threatening infections has been greatly reduced. However, the impact of HAART on the incidence of malignancy has been less clear. Published studies generally show that the risk of developing Kaposi's sarcoma declined by about two-thirds between 1994 and 1995 and from 1996 onward (considered the HAART era). Even before 1994, the risk for Kaposi's sarcoma in persons with AIDS had declined considerably and this cancer has now become relatively uncommon. The mechanism by which this decline in incidence was achieved appears to involve improved immunity. Data on the reduction in the risk for non-Hodgkin's lymphoma are mixed. Several studies conducted between 1997 and 1999 found no reduction in the risk for non-Hodgkin's lymphoma, although the most recent data (from 1997 to 1999) show a 42% decrease in risk. Even with a one-third reduction, the risk for non-Hodgkin's lymphoma remains considerably elevated. This high risk may be related to the fact that HAART therapy does not restore the immune system to normalcy. The increased lymphocyte turnover, with its accompanying risk of genetic errors, may increase the risk of developing non-Hodgkin's lymphoma. Most reports have insufficient data to analyze the impact of HAART therapy on incidence of central nervous system lymphomas, but recent data (from 1997 to 1999) showed a significant reduction in that risk. The mechanism by which this might occur is unclear because the central nervous system is an immunologic sanctuary. The relatively low incidence of other cancers in persons with AIDS makes it difficult to gauge the effect of HAART on their incidence, but to date, no significant trends have been reported for specific tumor types or for the overall risk of non-AIDS-related cancers.

Risk of T-cell lymphomas in persons with AIDS.

Lymphomas in persons with AIDS are mostly B-cell types, but T-cell lymphomas have also been reported. We examined T-cell lymphoma risk in the 2-year period after AIDS onset by linking 302,834 adults with AIDS to cancer registry data. Of 6,788 cases of non-Hodgkin's lymphoma (NHL) with specified histologies, 96 (1.4%) were T-cell lymphomas. Assessment was based on clinical diagnosis and histology because T-cell marker data were inadequate, but when present, marker data supported the T-cell diagnosis. The relative risk of T-cell lymphoma, estimated by standardized incidence ratio, was 15.0 (95% confidence interval: 10.0--21.7). Risks were increased for all subtypes, including mycosis fungoides, peripheral lymphomas, cutaneous lymphomas, and adult T-cell leukemia/lymphoma (ATLL). HIV-related immunodeficiency could be important, but differences between the population developing AIDS and the general population (e. g., immigration from the Caribbean region for ATLL) might independently increase T-cell lymphoma risk.

Association of cancer with AIDS-related immunosuppression in adults.

CONTEXT: Large-scale studies are needed to determine if cancers other than Kaposi sarcoma, non-Hodgkin lymphoma, and cervical cancer occur in excess in persons with human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS). OBJECTIVES: To examine the general cancer pattern among adults with HIV/AIDS and to distinguish immunosuppression-associated cancers from other cancers that may occur in excess among persons with HIV/AIDS. DESIGN, SETTING, AND SUBJECTS: Analysis of linked population-based AIDS and cancer registry data from 11 geographically diverse areas in the United States, including 302 834 adults aged 15 to 69 years with HIV/AIDS. The period of study varied by registry between 1978 and 1996. MAIN OUTCOME MEASURE: Relative risks (RRs) of cancers, calculated by dividing the number of observed cancer cases by the number expected based on contemporaneous population-based incidence rates. We defined cancers potentially influenced by immunosuppression by 3 criteria: (1) elevated overall RR in the period from 60 months before to 27 months after AIDS; (2) elevated RR in the 4- to 27-month post-AIDS period; and (3) increasing trend in RR from before to after AIDS onset. RESULTS: Expected excesses were observed for the AIDS-defining cancers, but non-AIDS-defining cancers also occurred in statistically significant excess (n = 4422; overall RR, 2.7; 95% confidence interval [CI], 2.7-2.8). Of individual cancers, only Hodgkin disease (n = 612; RR, 11.5; 95% CI, 10.6-12.5), particularly of the mixed cellularity (n = 217; RR, 18.3; 95% CI, 15.9-20.9) and lymphocytic depletion (n = 36; RR, 35.3; 95% CI, 24.7-48.8) subtypes; lung cancer (n = 808; RR, 4.5; 95% CI, 4.2-4.8); penile cancer (n = 14; RR, 3.9; 95% CI, 2.1-6.5); soft tissue malignancies (n = 78; RR, 3.3; 95% CI, 2.6-4.1); lip cancer (n = 20; RR, 3.1; 95% CI, 1.9-4.8); and testicular seminoma (n = 115; RR, 2.0; 95% CI, 1.7-2.4) met all 3 criteria for potential association with immunosuppression. CONCLUSION: Although occurring in overall excess, most non-AIDS-defining cancers do not appear to be influenced by the advancing immunosuppression associated with HIV disease progression. Some cancers that met our criteria for potential association with immunosuppression may have occurred in excess in persons with HIV/AIDS because of heavy smoking (lung cancer), frequent exposure to human papillomavirus (penile cancer), or inaccurately recorded cases of Kaposi sarcoma (soft tissue malignancies) in these persons. However, Hodgkin disease, notably of the mixed cellularity and lymphocytic depletion subtypes, and possibly lip cancer and testicular seminoma may be genuinely influenced by immunosuppression.

Latent class analysis of human herpesvirus 8 assay performance and infection prevalence in sub-saharan Africa and Malta.

Human herpesvirus 8 (HHV-8) is thought to be highly prevalent in Mediterranean countries and sub-Saharan Africa, where it causes Kaposi's sarcoma in a small proportion of infected immunocompetent persons. However, the lack of serological tests with established accuracy has hindered our understanding of the prevalence, risk factors and natural history of HHV-8 infection. We tested 837 subjects from Congo, Botswana (mostly young adults) and Malta (elderly adults), using an immunofluorescence assay and 2 enzyme immunoassays (EIAs, to viral proteins K8.1 and orf65). Each assay found HHV-8 seroprevalence to be high (49-87%) in the African populations and generally lower (9-54%) in Malta. However, there was only modest agreement among tests regarding which subjects were seropositive (3-way kappa, 0.05-0.34). We used latent class analysis to model this lack of agreement, estimating each test's sensitivity and specificity and each population's HHV-8 prevalence. Using this approach, the K8.1 EIA had consistently high sensitivity (91-100%) and specificity (92-100%) across populations, suggesting that it might be useful for epidemiological studies. Compared with the K8.1 EIA, both the immunofluorescence assay and the orf65 EIA had more variable sensitivity (80-100% and 58-87%, respectively) and more variable specificity (57-100% and 48-85%, respectively). HHV-8 prevalence was 7% among elderly Maltese adults. Prevalence was much higher (82%) in Congo, consistent with very high Kaposi's sarcoma incidence there. Prevalence was also high in Botswana (87% in Sans, an indigenous group, and 76% in Bantus), though Kaposi's sarcoma is not common, suggesting that additional co-factors besides HHV-8 are needed for development of Kaposi's sarcoma.

Human papillomavirus-associated cancers in patients with human immunodeficiency virus infection and acquired immunodeficiency syndrome.

BACKGROUND: Human papillomavirus (HPV)-associated anogenital malignancies occur frequently in patients with human immunodeficiency virus (HIV) infection and the acquired immunodeficiency syndrome (AIDS). The purpose of our study was to determine if the high frequency of these cancers is due to lifestyle factors associated with both HPV and HIV infections or to immunosuppression following HIV infection. METHODS: We studied invasive and in situ HPV-associated cancers among 309 365 U.S. patients with HIV infection/AIDS (257 605 males and 51 760 females) from 5 years before the date of AIDS onset to 5 years after this date. Sex-, race-, and age-standardized ratios of observed-to-expected cancers served as measures of relative risk (RR). Trend tests were used to evaluate changes in the RRs during the 10 years spanning AIDS onset. All statistical tests were two-sided. RESULTS: All HPV-associated cancers in AIDS patients occurred in statistically significant excess compared with the expected numbers of cancers. For in situ cancers, overall risks were significantly increased for cervical (RR = 4.6; 95% confidence interval [CI] = 4.3-5.0), vulvar/vaginal (RR = 3.9; 95% CI = 2.0-7. 0), anal (in females, RR = 7.8 [95% CI = 0.2-43.6]; in males, RR = 60.1 [95% CI = 49.2-72.7]), and penile (RR = 6.9; 95% CI = 4.2-10.6) cancers, and RRs increased during the 10 years spanning AIDS onset for carcinomas in situ of the cervix (P: for trend <.001), vulva/vagina (P: for trend =.04), and penis (P: for trend =.04). For invasive cancers, overall risks were significantly increased for cervical (RR = 5.4; 95% CI = 3.9-7.2), vulvar/vaginal (RR = 5.8; 95% CI = 3.0-10.2), and anal (RR = 6.8; 95% CI = 2.7-14.0) cancers in females and for anal (RR = 37.9; 95% CI = 33.0-43.4), penile (RR = 3. 7; 95% CI = 2.0-6.2), tonsillar (RR = 2.6; 95% CI = 1.8-3.8), and conjunctival (RR = 14.6; 95% CI = 5.8-30.0) cancers in males. However, RRs for invasive cancers changed little during the 10 years spanning AIDS onset. CONCLUSIONS: HPV-associated malignancies occur at increased rates in persons with HIV/AIDS. Increasing RRs for in situ cancers to and beyond the time of AIDS onset may reflect the gradual loss of control over HPV-infected keratinocytes with advancing immunosuppression. However, the lack of a similar increase for invasive HPV-associated cancers suggests that late-stage cancer invasion is not greatly influenced by immune status.

Changing patterns of tonsillar squamous cell carcinoma in the United States.

OBJECTIVE: Tonsillar squamous cell carcinoma (SCC) may differ etiologically from other oral cancers. The aim of this study was to provide a detailed description of the incidence patterns of tonsillar SCC in the United States. METHODS: Population-based incidence data from the Connecticut Tumor Registry (period 1945-1994) and from the SEER program (period 1973-1995) were used to calculate age-standardized (US 1970) and age-specific incidence rates and confidence intervals (CIs). Linear regression was used to evaluate trends. RESULTS: The incidence of tonsillar SCC increased fourfold among white women in Connecticut during 1945-1994 but remained rather constant in white men. During 1973-1995, incidence rates per million person-years were considerably higher in blacks (31.6; 95% CI: 29.0-34.4 in men, and 9.6; 95% CI: 8.3-10.9 in women) than whites (14.8; 95% CI: 14.3 15.3 in men, and 6.1; 95% CI: 5.8-6.4 in women). Men, but not women, who were younger than 60 years experienced significant annual increases in tonsillar SCC incidence during 1973-1995 (2.7% in blacks and 1.9% in whites). No similar increases occurred for oral SCC at non-tonsillar sites. CONCLUSION: Incidence rates of tonsillar SCC vary considerably by sex, race and time in a way that cannot be explained by changes in tonsillectomy practices alone. Changes in environmental risk factors, including changes in smoking patterns and an increase in oral human papillomavirus infections, may have contributed.

Risk of cancer in children with AIDS. AIDS-Cancer Match Registry Study Group.

CONTEXT: Population-based data on cancers associated with acquired immunodeficiency syndrome (AIDS) in children are lacking. OBJECTIVE: To determine risk of pediatric AIDS-associated cancers. DESIGN, SETTING, AND PARTICIPANTS: Using records from 11 locations in the United States for varying periods between 1978 and 1996, we linked data for children aged 14 years and younger at AIDS diagnosis to local cancer registry data. MAIN OUTCOME MEASURES: Cancer frequency and, in the 2-year post-AIDS onset period, cancer incidence and relative risk (RR; measured as standardized incidence ratio), by cancer type. RESULTS: Among 4954 children with AIDS, 124 (2.5%) were identified as having cancer before, at, or after AIDS onset, including 100 cases of non-Hodgkin lymphoma (NHL), 8 of Kaposi sarcoma (KS), 4 of leiomyosarcoma, and 2 of Hodgkin disease; there were 10 other or unspecified cancers. Expected numbers for all cancers identified in the study sample, based on population rates (using area-specific registry data), were less than 1. In the first 2 years after AIDS diagnosis (5485 person-years), NHL incidence was 510 per 100,000 person-years (RR, 651; 95% confidence interval [CI], 432-941). Median time for developing NHL after AIDS diagnosis was 14 months (range, 3-107 months). The most common type of NHL was Burkitt lymphoma. However, the risk of primary brain lymphoma (91 per 100,000 person-years) was especially high (RR, 7143; 95% CI, 2321-16,692), and 4 cases were diagnosed more than 2 years (range, 37-98 months) after AIDS onset. Leiomyosarcomas also tended to occur several years after AIDS onset, with 3 of the 4 cases occurring 33 to 76 months after AIDS diagnosis, whereas KS was reported only at or within 2 years of AIDS diagnosis. Hodgkin disease risk was also significantly increased (RR, 62; 95% CI, 2-342). CONCLUSIONS: The spectrum of AIDS-associated pediatric cancers resembled that seen in adults, with the addition of leiomyosarcoma. Both primary brain lymphomas and leiomyosarcomas tended to occur in children surviving several years after AIDS onset. Because the expected numbers of these cancers in this population were less than 1 and because of the small numbers of some types of observed cancers, the RR estimates are imprecise and caution is warranted in their interpretation. JAMA. 2000;284:205-209

Identifying human herpesvirus 8 infection: performance characteristics of serologic assays.

Epidemiologic studies of infection with the oncogenic human herpesvirus 8 (HHV-8) depend on serologic methods to diagnose infection. However, optimal strategies for identifying HHV-8 infection remain undefined. We therefore evaluated four enzyme-linked immunoassays (EIAs) and one immunofluorescence assay (IFA) using sera from 87 individuals with the prototype HHV-8 disease, Kaposi's sarcoma (KS), and 210 participants in a hemophilia study (who were presumed not to be infected with HHV-8). Assays performed reasonably well in distinguishing between infected and uninfected persons, with receiver operator curve areas between 0.86 and 0.96. Nonetheless, IFA had only 86% sensitivity and 88% specificity, and no EIA simultaneously had sensitivity and specificity above 90% for any of the optical density (OD) cutpoints used to define seropositivity. Some assays were markedly less sensitive with diluted KS sera, suggesting that they poorly identify low-titer antibodies present in asymptomatic infection. We also developed a classification tree that categorized individuals as seropositive if they had OD > 2.00 on recombinant K8.1 protein EIA or if they had both K8.1 OD between 0.51 and 2.00 and positive IFA results; this strategy had between 80% and 90% sensitivity and 95% and 100% specificity. Overall, assays performed adequately for use in most epidemiologic investigations, but wider applications will require improved tests.

Human herpesvirus 8 in Brazilian Amerindians: a hyperendemic population with a new subtype.

Human herpesvirus 8 (HHV-8) epidemiology in Brazilian Amerindians was studied. Use of an immunofluorescence (IFA) test for latent antibody demonstrated that the prevalence of HHV-8 in 781 Amerindians of diverse tribes (overall, 53% prevalence) was not related to language group or sex but rather increased gradually from 41% in children <10 years of age to 65% in adults >/=30 years of age. In IFA-positive subjects, HHV-8 DNA was detected in 3 (16%) of 19 mononuclear cell samples from peripheral blood and in 1 of 16 saliva samples. The sequences of conserved ORF22 and K6 genes were typical of HHV-8, but the variable K1 gene sequences were only 70%-75% identical to other known HHV-8 strains. Thus, a new HHV-8 subtype, E, is hyperendemic in Brazilian Amerindians, although Kaposi's sarcoma has not been reported. Transmission is probably oral rather than sexual. The limited genetic pool in isolated groups may permit more frequent transmission of a virus with a low prevalence in heterogeneous populations.