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For better understanding of the role of humoral immunity in ameliorating infections with rotavirus (RV) and Norwalk virus (NW), 305 Cuna Indians living on two isolated islands located off Panama's Carribean coast were surveyed daily for diarrhea over a seven-month period. Nine (8%) of 108 persons with a baseline RV antibody titer of greater than 1:4 developed RV infection compared with 70 (46%) of 151 persons with a baseline RV antibody titer of less than 1:4 (P less than .001). Thirty-eight (25%) of 151 persons of all ages with baseline RV antibody titer of less than 1:4 had at least one episode of RV diarrhea compared with 6 (6%) of 108 persons who had baseline RV antibody titers of greater than 1:4 (P less than .001). Thirty-two (47%) of 68 persons of all ages who had a baseline NW antibody titer of less than 1:100 developed NW infection compared with 30 (13%) of 237 persons with a baseline NW titer of greater than 1:100 (P less than .001). The high NW and RV infection rates and the excellent levels of protection provided by specific preexisting humoral antibody to these agents should promote activities aimed at developing vaccines for preventing these infections.

A case-control study of 667 patients with invasive squamous cell carcinoma of the cervix and 1,430 controls from four Latin American countries showed an age-adjusted relative risk (RR) of 1.2 [95% confidence interval (CI) = 1.0-1.4] for women who had ever smoked, with risk rising to 1.7 (95% CI, 0.8-3.6) for women who smoked greater than or equal to 30 cigarettes per day. The associations were practically eliminated after adjustment for the number of sexual partners and alcohol consumption, probably a surrogate for an unidentified life-style risk factor. Some excess risk persisted among women who smoked for extended periods (RR = 1.5 for greater than or equal to 40 yr), as well as those who began smoking at older ages (RR = 1.7 for greater than 30 yr), which suggests a late-stage effect. In addition, among women who tested positive for human papillomavirus (HPV) type 16 or 18 by filter in situ hybridization, there was an increased risk for women who had ever smoked and a dose-response relationship with the number of cigarettes smoked (adjusted RRs compared with HPV-negative nonsmokers = 5.0 for HPV-positive nonsmokers, 5.5 for less than 10 cigarettes/day, and 8.4 for greater than or equal to 10 cigarettes/day). In contrast, HPV-negative women had no increased risk associated with smoking. These results, from a high-incidence area where intensive smoking among women is still relatively rare, suggest that smoking has a limited effect on cervical cancer risk, possibly only among women with specific types of HPV.

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Cerebellar symptoms at onset are unusual in HTLV-I/II-associated tropical spastic paraparesis (TSP). A prospective study of neurological disorders in Panama (1985-1990) revealed 13 patients with TSP and 3 with HTLV-I/II-associated spinocerebellar syndrome (HSCS) presenting at onset loss of balance, wide-based stance and gait, truncal instability, and mild leg ataxia (vermian cerebellar syndrome), with absent upper limb dysmetria but with postural tremor, downbeat nystagmus, and dysarthria. In 4-5 years, spinal cord manifestations of TSP developed, including spastic paraparesis, pyramidal signs, bladder and sphincter disturbances. Two patients were infected with HTLV-I and another one, a Guaymi Amerindian woman, with HTLV-II. Magnetic resonance imaging (MRI) demonstrated cerebellar atrophy involving predominantly the superior vermis. Mild axonal peripheral neuropathy in the lower limbs, dorsal column involvement and inflammatory myopathy were found by neurophysiology studies. There are 14 similar cases reported in Japan and Canada, but to our knowledge these are the first documented cases of HSCS in the tropics. A cerebellar syndrome constitutes another form of presentation of HTLV-I/II infection of the nervous system.

Human T-cell lymphotropic virus type I (HTLV-I) infection and associated hematologic malignancies cluster in Japan, the Caribbean basin, and Central Africa. The authors believe that this study of HTLV-I seroepidemiology in the Republic of Panamá is the first detailed analytic study of environmental factors pertaining to HTLV-I infection in representative tropical populations. The study analyzed observational data concerning housing conditions, family composition, and demographic and behavioral attributes as risk factors for HTLV-I infection (HTLV-I antibody). The 745 study subjects were residents of representative households in Panamá City and Colón. Overall, 5% of sera had antibody against HTLV-I, detected by enzyme-linked immunosorbent assay and confirmed by competitive binding. Housing conditions, race, and socioeconomic factors were not associated with infection nor did infection cluster in families. Interview of 706 women enrolled in cervical cancer studies documented that female sexual experience (number of marriages or sexual partners) was associated with HTLV-I infection. These findings support the hypothesis that HTLV-I is not transmitted by casual contact but requires exposures involving exchange of bodily fluids.