The human T-lymphotropic virus type 1 (HTLV-1) and type 2 (HTLV-2), were the first retrovirus discovered in humans and named as such because they inhabit the T-lymphocytes. Both mainly transmitted by being transferred from mother to child due infected lymphocytes in breastfeeding or from a man to a woman by semen. HTLV-1 is the causative agent of an incapacitating myelopathy (HAM/TSP) and Adult T-cell leukemia / lymphoma (ATLL), among other diseases. The high endemicity of such viruses in households of the metropolitan area of Belém-Pará requires investigations to better characterize this viral spread and morbidity. This study was developed in order to identify and characterize the clinical diversity and peculiarities the HTLV transmission in families of the metropolitan region of Belém-Pará. Between 2007 and 2015, we investigated 178 family groups that are confirmed carriers of the virus (index cases). From these families, 140 have HTLV-1 and 38 have HTLV-2, of which 433 members were spontaneously subjected to serologic testing of anti-HTLV-1/2 antibodies. Such test consists on the ELISA method and the detection test of proviral DNA in the blood (PCR). Routes of infection and clinical aspects were evaluated in all individuals and families. From the 611 surveyed 64.6% are female and 37.9% male with, mean age of 41 years. The transmission of HTLV occurred in 92 families (51.8%) with occurrence of three to four infected per family. The infection was more prevalent in females (p< 0.0001) and sexual contact was greater than the vertical (p = 0.0002). 44.3% (62/140) from the index cases of HTLV-1 and 9.9% of their family contacts (11/111) were recognized as symptomatic. The most common diagnostic modalities were neurological (21.4%) and dermatological (19.3%), with a prevalence of neuromuscular osseous symptoms, dysautonomia and skin changes. The main diseases caused by the HTLV-1, out of the 251 infected cases, were: HAM/TSP 7.2% (18); Lymphoproliferative Diseases 2.6 % (6); Strongyloides hyper infection 1.6% (4); Dermatitis Infective in 1.2% (3) and uveitis in 0.4% (1). The parenteral route was the most common form of transmission of HTLV-1 in the causation of neurological diseases (HAM/TSP) whereas the vertical route was the most common form in lymphoproliferative diseases (including ATLL). In some families, HTLV-1 was inlaid spread for generations in a "sui generis" form, mimicking a genetic factor, differentiating itself from other pathogens. It was also observed unmistakable versatility of HTLV-1 to cause a variety of clinical diseases in human bodies, many of them setting well-defined diseases as the causal virus.
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