Estimating the time of HTLV-I infection following mother-to-child transmission in a breast-feeding population in Jamaica

Mother-to-child transmission of human T-cell lymphotrophic virus type 1 (HTLV-I) is primarily due to prolonged breast-feeding (>6 months) in the post-natal period. Most infant infections are not identifiable until 12-18 months of age by available whole virus Western blot serologic tests because of their inability to distinguish passively transferred maternal antibody from infant antibody. We investigated two methods to assess more accurately the time of infant infection. In prospectively collected serial biospecimens, HTLV-I-specific immunoglobulin (Ig) isotypes of IgM and IgA were determined by Western blot and HTLV-I proviral DNA was detected by polymerase chain reaction (PCR). IgA and IgG reactivity was assessed in periodic serum samples from 16 HTLV-I-seropositive children while IgM reactivity was observed in 100 percent of children at 24 months of age and 73 percent of children at 6-12 months of age; however, this could represent maternal and not infant antibody. Both IgA and IgM reactivity were insensitive indicators of infection, with only 50 percent of children showing reactivity at 24 months of age. PCR testing was performed in biospecimens obtained from 11 of these children. An estimated median time of infection of 11.9 months was determined by PCR, which was similar to the median time to infection determined by whole virus Western blot (12.4 months; P=0.72). PCR Tests support a median time to infection that is similar to that estimated by whole virus Western blot. (AU)

A study of adult T-cell leukemia/lymphoma incidence in central Brooklyn

Adult T-cell leukemia/lymphoma (ATL), a rare outcome of infection with human T-lymphotropic virus (HTLV-I), is endemic in central Brooklyn, which has a large Caribbean migrant population. Previous studies have suggested that HTLV-I prevalence in central Brooklyn may be similar to that recorded in the Caribbean islands. We established a pilot 1-year surveillance program to identify cases of ATL in 7 of 10 hospitals serving the residents of 18 zip codes of central Brooklyn with a combined population of 1,184,670. Of the 6,198 in-patient beds in the catchment area, approximately 83 percent were covered. Twelve incident cases of ATL were ascertained, all among persons of Afro-Caribbean descent, indicating an annual incidence in African-Americans in this community of approximately 3.2/100,000 person-years. Unexplained hypercalcemia was the most useful screening method, identifying 3 of 5 patients not referred for possible ATL by a local hematologist. The female:male ratio was 3:1. The age pattern was different from that reported in the Caribbean Basin and closer to the pattern seen in Japan. Our study supports evidence that HTLV-I infection and ATL are endemic in central Brooklyn and suggests that a more intensive surveillance program for this disease coupled with intervention efforts to reduce HTLV-I transmission are warranted.(Au)

Seroprevalence of HTLV-I and HTLV-II among a cohort of HIV-infected women and women at risk for HIV infection. Women's Interagency HIV Study

OBJECTIVES: To determine the seroprevalence of, and risk factors for, HTLV-I and HTLV-II infection among HIV-infected women and women at high risk for HIV infection. DESIGN: Cross-sectional analysis of baseline data for women enrolled in the prospective Women's Interagency HIV Study (WIHS). METHODS: From October 1994 through November 1995, 2657 women from five metropolitan areas in the United States (Chicago, Los Angeles, New York City [two sites], Northern California, and Washington DC) were enrolled in WIHS. An interview-based survey collected data on demographics, behavior, and medical history. HTLV-I and HTLV-II determinations were made using a combined HTLV-I/HTLV-II indirect immunofluorescent antibody (IFA) screening test, an IFA titration specificity test, and individual HTLV-I and HTLV-II confirmatory Western blots. Fisher's exact tests and logistic regression were used to determine univariate and multi variate independent predictors for HTLV-II infection. RESULTS: Of 2625 women enrolled in WIHS with confirmed HIV results, 2487 (95 percent) were tested for HTLV-I and HTLV-II. Of these, 241 (10 percent) HTLV-II-seropositive and 13 (0.5 percent) were HTLV-I-seropositive. On multivariate analysis, independent predictors of HTLV-II infection included injection drug use (OR = 5.2; p < .001), black race (OR = 3.6; p < 0.001), age > 35 years (OR = 3.3; p < .001) and a history of sex with a male injecting drug user (OR = 1.9; p < .001). Among women injected with HIV, the seroprevalence of HTLV-II was 11 percent compared infected with HIV, the seroprevalence of HTLV-II was 11 percent compared with 6 percent for women at risk for HIV but not infected (p < .001). However, HIV was not an independent predictor of HTLV-II infection in multivariate analysis. CONCLUSIONS: This cross sectional analysis confirms that HTLV-II is found commonly in HIV-infected women at risk for HIV in major urban areas throughout the United States and that HTLV-II is far more common than HTLV-I in these populations. Although injecting drug use is most strongly associated with HTLV-II infection, sexual transmission likely contributes to the high HTLV-II seroprevalence in this cohort.(AU)

Incidence of HIV and HTLV-1 infection among sexually transmitted disease clinic attenders in Jamaica

Of 970 sexually transmitted disease (STD) patients enrolled at the Comprehensive Health Centre, Kingston, Jamaica, between November 1990 and January 1991, 710 (73 percent, 333 men and 377 women) were reexamined between January 1992 and July 1993 to estimated the incidence of HIV and HTLV-1 infection and to identify risk factors for infection. Of those reexamined, 20 percent were recruited passively when they returned to the clinic of their own accord, and 80 percent were recruited actively through field visits to their homes. Passively recruited persons were significantly more likely than active recruits to have had a sexually transmitted disease since enrollment or at their follow-up visit. Seven men and one women became HIV positive during the period of follow-up. The overall HIV incidence rate was 0.7 per 100 person years (95 percent confidence interval [CI] = 0.3 to 1.4 (CI = 0.6 to 2.8) for men and 0.2 (CI = 0.004 to 0.9) for women. Four of 270 men and 4 of 318 women were HTLV-1 positive, and overall incidence of 0.9 per 100 person years (CI = 0.4 to 1.7), 1.0 for men and 0.8 for women. HTLV-1 infection was associated with an age of 30 years or older (p < 0.01). The presumed lower transmission probability for HTV-1 may combine with a higher prevalence of HTLV-1 in sexual partners to produce similar overall incidence rates for the two infections. The HIV and HTLV-1 incidence rates may have been underestimated, because the study subjects who did not return to the clinic may have had a somewhat higher risk. On univariate analysis, there were significant associations between HIV infection in men and drinking alcohol before sex, cocaine use, total number of sex partners, sex with a prostitute since enrollment, ever accepting money for sex, the average number of sex partner per month, bruising during sex, and genital ulcers found on follow-up examination. This analysis needs to be interpreted with caution in view of the small number of seroconverters, which did not allow testing for independent effects in a logistic regression model(AU)

A case-control study of risk factors for seropositivity to human T-lymphotropic virus type I (HTLV-I) in Jamaica

BACKGROUND: We investigated behavioural and environmental risk factors for seropositivity to human T-lymphotropic virus type I (HTLV-I). METHODS: A nested case-control study of 201 HTLV-I seropositive subjects and 225 age and sex matched seronegative controls was performed using questionaire data from the enrollment visit of a cohort study in 1987-1988. HTLV-I serostatus was confirmed using enzyme-linked imunosorbent assay (ELISA) and Western blot. RESULTS: Among women, the number of lifetime sexual partners (P < 0.05, chi 2 trend) and the number of different men fathering a child by the woman (P < 0.06, chi 2 trend) were associated with HTLV-I seropositivity. Use by the female subject of an intrauterine device (IUD) was associated with an increased risk of seropositivity (odds ratio (OR) = 2.67, 95 percent confidence interval (CI): 1.13-6.23); condom use was rare in this population. Among male subjects, a larger number of lifetime sexual partners was also associated with HTLV-I seropositivity (P < 0.05, chi 2 trend). No association was found between HTLV-I seropositivity and educational attainment, income, or occupation. Having been breastfed as a child or receipt of a blood transfusion had elevated but imprecise OR due to very high and low prevalence of the risk factors, respectively. Several variables relating to insect or animal exposure showed no association with HTLV-I seropositivity. CONCLUSIONS: These data confirm that heterosexual intercourse is a major route of HTLV-I transmission, but do not support suggestions of insect or environmental vectors.(AU)

Differential patterns of serum biomarkers of immune activation in human T-cell lymphotropic virus type I-associated myelopathy/tropical spastic paraparesis, and adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) and human T-cell lymphotropic virus type I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) are associated with differing patterns of immune dysfunction. Biomarkers of immune activation may correlate with perturbations of immune function associated with these diseases. We conducted a pilot cross-sectionalstudy to assess four candidate biomarkers of immune activation, beta 2-microglobulin, neopterin, tryptophan, and kynurenine levels were assayed in storedsera from asymptomatic, human T-cell leukemia virus type I (HTL V-I) seronegative (HTLV-I-) and HTLV-I-seropositive (HTLV-I+) individuals, and ATL and HAM/TSP patients previously enrolled in seroepidemiological studies in Jamaica. Mean levels of beta 2-microglobulin, neopterin, and kynurenine were significantly elevated among ATL patients compared to the other study groups. Mean tryptophan levels were signigicantly lower among ATL and HAM/TSP patients than HTLV-I- and HTLV-I+ groups. No significant differences in biomarkers were found between HTLV-I- and HTLV-I+ groups. Among HAM/TSP patients, a significant association was found between elevated neopterin levels and symptoms of less than 4 years duration. In Cox proportional hazards regression modeling, neopterin and tryptophan were found to be independent predictors of survival among ATL patients. This study demonstrates a differential pattern of biomarkers of immune activation among ATL and HAM/TSP patients compared to HTLV-I- amd HTLV-I+ individuals. Neopterin and tryptophan may be useful clinical indicators of disease severity and prognosis among HAM/TSP and ATL patients. (AU)

Human T-cell lymphotropic virus type 1 infection in Barbados: results of a 20-year follow-up study

Forty-one human T-cell lymphotropic virus I (HTLV-1)-seropositive individuals were identified among 1,012 subjects with stored serum samples from a health and seroepidemiological survey conducted in Barbados in 1972. These 41 subjects plus 79 HTLV-1 seronegative household members were targeted in a follow-up study 20 years later. Sixteen seropositive subjects and 22 seronegative subjects were interviewed, examined, and phlebotomized. There were no changes in HTLV-1 serostatus between the 1972 and follow-up serum samples. Three (19 percent) of the seropositive subjects had HTLV-1 serostatus between the 1972 and follow-up serum samples. Three (19 percent) of the seropositive subjects had HTLV-1-associated disorders: two with dermatitis and one with <

Anterior horn cell degeneration in polymyositis associated with human T lymphotropic virus Type-1 in patients from Barbados

Anterior horn cell degeneration has only ocassionally been noted in patients with tropical spastic paraparesis associated with human T lymphotropic virus type-1 (HTLV-1) infection. We report on three adult patients with HTLV-1-associated polymyositis who had clinical evidence of anterior horn cell degeneration. One patient had moderate proximal weakness and muscle wasting in all four limbs, while two had mild upper limb weakness with more profound proximal weakness and wasting in the lower limbs. In all three patients, elctromyographic findings were compatible with motor unit loss and muscle biopsies showed mononuclear inflammatory cell infiltration; muscle cell biopsies in two patients showed features of denervation. Immunoglobulin G (IgG) antibodies to HTLV-1 were detected by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western immunoblot in serum and cerobrospinal fluid in all three patients. In two, cell cultures were established from peripheral blood lymphocytes and HTLV-1 antigen was identified by immunofluorescence and the ELISA antigen-capture technique using an anti-p19 HTLV-1 mouse monoclonal antibody. The three cases illustrate the variety of neuromuscular disease, other than spastic paraparesis, that may occur in HTLV-1 infection. In some cases of HTLV-1-associated polymyositis, anterior horn cell degeneration may make a significant contribution to the muscle atrophy observed. (AU)

Human T cell lymphotropic virus (HTLV-1): cutaneous manifestations

Skin manifestations are a common feature of HTLV-1 associated disorders and of HTLV-1 infection itself. These include the lymphomatous skin infiltrates in adult T-cell lymphoma/leukaemia, most commonly manifesting as persistent, generalised papules, nodules and plaques with later ulceration, acquired ichthyosis and xeroderma in HAM/TSP, infective dermatitis of children, dermatomyositis, crusted (Norwegian) scabies, psoriasiform rashes which may precede one of the more serious disease associations, and possibly also seborrhoeic dermatitis. Disorders typically associated with immunosuppression such as disseminated herpes zoster, and ulcerative non-healing herpes simplex may also be seen occasionally both in ATK as well as in other wise asymptomatic HTLV-1 infection (AU)

Identification of human T-cell leukemia/lymphoma virus type I antibodies, DNA, and protein in patients with polymyositis

OBJECTIVE: To investigate a possible association between human T cell leukemia/lymphoma virus type I (HTLV-I) and polymyositis (PM). METHODS: Sera and muscle biopsy samples from 9 Jamaican PM patients were compared with specimens from American HTLV-I positive PM patients and normal controls. Sera were evaluated for HTLV antibodies by enzyme-linked immunosorbent assay and Western blot. The biopsy samples were analyzed for HTLV-I/II DNA by polymerase chain reaction and were also immunohistochemically stained for HTLV gp46 envelope protein. RESULTS: Seven of the 8 Jamaican PM patients from whom sera were available were HTLV-I seropositive. The muscle biopsies of all 9 Jamaican patients demonstrated severe lymphocytic infiltration, cellular degeneration, myofiber atrophy, and fibrosis. Each muscle biopsy specimen contained HTLV-I DNA. Two of 6 samples demonstrated intense staining for HTLV-I gp46 in many of the invading mononuclear cells and weak staining for HTLV-I gp46 in many of the other specimens were weakly positive for gp46 in rare mononuclear cells. All controls specimens were negative for the presence of HTLV-I DNA and protein. CONClUSION: HTLV-I is associated with an inflammatory muscle disease characterized by direct invasion of the affected muscle by HTLV-I-infected mononuclear cells.(AU)

Risk factors for HTLV-I among heterosexual STD clinic attenders

Human T-cell lymphotropic virus type 1 (HTLV-I) status was assessed in 994 patients attending a sexually transmitted disease (STD) clinic in Kingston, Jamaica, between November 1990 and January 1991 for a new STD complaint. Of 515 heterosexual men, 36 (7.0 percent) were HTLV-I seropositive, as were 38 (7.9 percent) of 479 women. HTLV-I seroprevalence increased with age in women. A history of blood transfusion was associated with HTLV-I in both sexes, significantly so in men [odds ratio (OR) 4.7, confidence interval (CI) 1.1-17 for men; OR 1.9, CI 0.6-5.0 for women]. Further analysis excluded all persons reporting a transfusion. On multiple logistic regression analysis, independent associations with HTLV-I infection in men were shown for marital status (OR 3.5, CI 1.2-10 for married/common law vs. single/visiting unions), agricultural occupation (OR 9.0, CI 2.0-41), bruising during sex (OR 2.9, CI 1.0-8.1), o 15 years at first sexual intercouse (OR 2.9, CI 1.0-8.2), and a positive test for hepatitis B surface antigen (OR 7.3, CI 1.2-52). In women, associations were shown for two or more sex partners in the 4 weeks prior to complaint (OR 4.9, CI 1.8-13), 11 or more lifetime sexual partners (OR 5.9, CI 1.3-27), aged < 15 years at first sexual intercouse (OR 2.3, 1.0-5.4), bruising during sex (OR 2.7, CI 1.1-6.6), microhaemagglutination-Treponema pallidum positivity (OR 3.6, CI 1.6-8.4), human immunodeficiency virus infection (OR 14, CI 2.1-92). STDs and bruising during sex may facilitate sexual transmission of HTLV-I, whereas sexual activity is a more important risk factor in women than men. Programs promoting safer sexual practices and controlling STDs may reduce HTLV-I infection in Jamaica (AU)

Human T-cell lymphotropic virus type I and severe neoplasia of the cervix in Jamaica

Human T-cell lymphotropic virus type I (HTLV-I) was associated with carcinoma of the cervix in Japan in a recent study that compared hospital cases with healthy population-based controls. To test this relationship in women more alike for cervical neoplasia risk factors (including sexual behavior and human papilloma virus: HPV), we enrolled consecutive patients from a colposcopy clinic in Kingston, Jamaica (an HTLV-1 endemic area). Patients underwent Pap smear, calopscopy, biopsy and cervical swab for detection of HPV by polymerase chain reaction. Cases were defined as women with CIN-3 or invasive cancer (CIN-3/CA). Controls included all patients with either CIN-1 or koilocytotic atypia, atypical squamous cells of undetermined significane or benign cervical pathology (all but one had at least inflammatory changes). Patients with CIN-2 were excluded to minimize risk of case-control misclassification. Cases were much more likely to be HTLV-1 seropositive than controls. Although mean age differed significantly between cases (mean age = 39 years) and controls (mean age = 33 years), control for age did not explain the relation of CIN-3/CA with HTLV-1. Among HPV DNA positive subjects the age-adjusted association was not diminished but lost statistical significance. HTLV-1 seroprevalence may be independently associated with progression to severe neoplasia of the cervix (AU)

Frequency and time course of seroconversion in maternal and infant transmission of HTLV-1 (abstract)

Objectives: To characterize the frequency and timecourse of seroconversion in infants acquiring HTLV-I infection from their mothers. Methods: 220 children born to HTLV-I seropositive women in Kingston, Jamaica were followed regularly for up to 36 months following birth. At each visit, mothers were interviewed and children were examined and blood samples taken. Results: A total of 30 children have seroconverted, including 17/86 (20 percent) of those completing >/= 24 months of follow-up. Analysis of serial Western blots (WB) on 7 seroconverters revealed maternal antibodies persisting for 7.3 months ([mean], [range 7.0 - 7.4]), followed by an absence of any antibody response lasting 8.3 months ([mean], [range 2.8 - 14.2]), followed by seroconversion (gag+env), occuring at 14.1 months ([mean], [range 9.8 - 21.5]). Six of these children were breast-feeding at the time of seroconversion and one had stopped breast feeding 8 months prior to seroconversion. Two mothers lacking gag antibody p24 on WB transmitted virus to their offspring. Conclusion: HTLV-I seroconversion in infants seems to occur only after the disappearance of maternal antibody, suggesting that this antibody may be protective, and raising the possibility that an HTLV-I vaccine could prevent transmission of virus. Current WB criteria that require presence of p24 antibody do not identify all individuals capable of transmitting HTLV-I

Viral specific humoral immune responses following transfusion-related transmission of human T cell lymphotropic virus type-I infection

The immunoglobulin (Ig) isotypes of antibodies to specific proteins of the human T cell lymphotropic virus type I (HTLV-I) were determined by Western blot analysis of serial specimens from six individuals who experienced HTLV-I seroconversion following blood transfusion; five remained asymptomatic carriers, while one developed HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) 32 weeks posttransfusion. Analysis of Ig isotypes demonstrated that while IgM was the most frequent early response to gag (p19, p24) and env (r21e) proteins within the first 3 months following transfusion, IgG and IgA responses could also be detected within this period. HTLV-I-specific antibody responses plateaued in all Ig isotypes, including IgM, wtihin the next 4- to 6-months period following transfusion and pesisted through the entire study period (> 4 years). Comparison of antibody profiles in Ig isotypes and IgG1 and IgG3 subclass among asymptomatic carriers and one individual who developed HAM/TSP demonstrated no evidence of isotypic prominence or IgG subclass restriction in either group. These results indicate the appearance of HTLV-I-specific IgM that persists even after the primary infection and suggest that such responses does not appear to provide an early marker of seroconversion. Further, we found no evidence of isotypic prominence or restriction of the antibody response in recipients who remained asymptomatic compared to one who developed HAM/TS.(AU)

Role of HTLV-I in development of non-Hodgkin lymphoma in Jamaica and Trinidad and Tobago. The HTLV lymphoma study group

Human T-cell lymphotropic virus type I (HTLV-I) has been implicated in the aetiology of adult T-cell leukaemia/lymphoma in Japan and elsewhere, particularly the Caribbean. We have carried out parallel case-control studies in Jamaica and in Trinidad and Tobago to quantify the role of HTLV-I in the development of non-Hodgkin lymphoma (NHL). 135 cases of NHL were enroled in Jamaica and 104 in Trinidad and Tobago. Controls were selected from patients treated in the same wards or clinics at the same time as the cases. Overall, patients with NHL were 10 times more likely than were controls to be seropositive for HTLV-I (Jamaica odds ratio 10.3 [95 percent CI 6.0-18.0], Trinidad and Tobago 14.4 [7.6-27.2]). In both countries the association between NHL and HTLV-I was greatest for T-cell lymphomas (18.3 [9.5-35.6] and 63.3 [25-267]). Among T-cell lymphomas especially, there was no significant difference between men and women in the association between NHL and HTLV-I, but there was a significant inverse relation between age and likelihood of HTLV-I seropositivity. B-cell lymphomas were predominant in the older age groups and were not associated with HTLV-I seropositivity. These findings are consistent with the hypothesis that early life exposure to HTLV-I is important for risk of subsequent ATL. Prevention of vertical transmission of HTLV-I could reduce by 70-80 percent cases of NHL in people under 60 years in this region (AU)

Mother-to-child transmission of human T-cell lymphotropic virus type I (HTLV-1) in Jamaica: association with antibodies to envelope glycoprotein (gp46) epitopes

To study mother-to-child transmission of HTLV-I in Jamaica, we screen antenatal patients in Kingston, Jamaica, from 1983 to 1985. Of 2,329 women, 81 (3.5 percent) were HTLV-I seropositive. Two to three years later, 36 seropositive mothers were recontacted, and blood was drawn from them and their children. All sera were tested for HTLV-I antibodies, and mother's sera were additionally tested for HTLV-I whole-virus antibody titer, syncytium-inhibition neutralizing antibody liter, and titers to six synthetic peptides from the HTLV-I envelope glycoprotein gp46. Seventeen of 74 (23 percent) [95 percent confidence interval (CI) 15-34 percent] children were seropositive. HTLV-I transmission was associated with breast-feeding duration > 6 months [relative risk (RR) 3.2; CI 0.4-22.1], maternal age > 30 years (RR 2.8; CI 1.0 - 7.8), and higher maternal whole-virus antibody titer (RR 3.3; CI 1.3 - 8.5). After controlling for higher whole-virus antibody titer, transmission remained associated with higher titer of neutralizing antibody and higher titer of antibody to the peptide sp4al, corresponding to amino acids 196 - 209 of the gp46 envelope glycoprotein. We conclude that mother-to-child transmission of HTLV-I in Jamaica is associated with longer duration of breast-feeding, older age, and higher HTLV-I antibody titer, in particular to a certain immunogenic portion of the gp46 envelope glycoprotein.(AU)

A prospective study of transmission by transfusion of HTLV-I and risk factors associated with seroconversion

To evaluate the risk of transfusion-related transmisssion of HTLV-I in Jamaica, a prospective study was initiated, prior to availability of a licensed HTLV-I serological screening assay. This information would prove useful in formulating strategies for blood-donor screening. We followed 118 pre-transfusion HTLV-I-negative transfusion recipients at monthly intervals post-transfusion for 1 year. Laboratory and questionnaire data were obtained at each visit to evaluate the clinical and immunological status of recipients. Cumulative incidence of HTLV-I seroconversion was estimated and risk-factor data associated with seroconversion among 66 HTLV-I-exposed transfusion recipients were analyzed. Seroconversion occurred in 24/54 (44 percent) of recipients of HTLV-I-positive cellular blood components, 0/12 recipients of positive non-cellular donor units and 0/52 recipients of HTLV-I-negative donor units. Significant risk factors associated with recipient seroconversion were receipt of a seropositive cellular blood component stored for less than one week odds ratio (OR) = 6.34, 95 percent confidence interval (CI) = 1.83 to 21.92], male sex (OR = 4.79, 95 percent CI = 1.15 to 20.0) or use of immunosuppressive therapy at time of transfusion (OR = 12.20, 95 percent CI = 0.95 to 156). Risk of blood-borne infection per person per year in Jamaica was estimated to be 0.009 percent. Our results confirm that blood transfusion carries a significant risk of HTLV-I transmission and that screening of donor blood effectively prevents HTLV-I seroconversion. Recipients at greatest risk for seroconversion were those who required multiple transfusions or who were receiving immunosuppressive therapy at the time of transfusion. These patients should be given priority in receiving selectively screened blood components, if universal blood-donor screening for HTLV-I is not possible (AU)

HTLV-1 and dengue seropositivity in Montserrat - abstract

Over 80 percent of the adult population of three villages in Montserrat donated blood samples for screening for HTLV-I and dengue antibodies. Twenty-five (7.2 percent) of the 349 samples tested were positive for HTLV-I antibodies and 17 of them live in 4 clusters of neighbouring households which was statistically significant. This clustering was not primarily due to viral or mother-to-child transmission but was the result of related and unrelated seropositive individuals living near to each other far more frequently than by chance alone. Two hundred and two (61 percent) of 331 samples tested were seropositive for dengue. Dengue seropositivity prevalence rates increased markedly with age and showed a strong difference in prevalence by altitude. This high prevalence of dengue seropositivity was surprising since no epidemics of dengue fever were reported in Montserrat. There is no evidence to support the hypothesis that the same insect vectors have a role in both dengue and HTLV-I transmission. However, the clustering observed, the inverse relation between HTLV-I sero prevalence and altitude and the failure of HTLV-I to establish itself in temperate climates, justify the need for further studies (AU)