Epidemiology

HTLV-2

Prevalence

Until recently, there was no information available to differentiate HTLV-II from HTLV-I, due partly to lack of serologic tests related to seroepidemiology or modes of transmission of HTLV-II. HTLV-II is prevalent among intravenal drug users, in the USA and Europe (52,53); more than 80% of HTLV-II seropositive in drug users in the USA is due to HTLV-II infection (54). HTLV-II seems also to be endemic in Native-American (Indigenous) populations, including the Guaymi in Panama (55) and the Native-Americans (Indigenous groups) from Florida (56), and New Mexico (57). HTLV-II-infected blood donors reported, with frequency, either a history of intravenal drug use or sexual contact with an intravenal drug user (6, 58). There is a reference of less percentage with history of blood transfusion. In Brazil, intravenal drug use is also an important form of contamination. Thus, individuals infected by the HIV-1, hepatitis C virus, hemodialysis clients should be tested for anti-HTLV-I/II antibodies.

Transmission

It is assumed that the HTLV-II is transmitted the same way as the HTLV-I; however, we know less about the specific modes and the efficiency of the HTLV-II transmission. A study conducted with 20 non-breastfed children born from women infected by the HTLV-II, in the city of New York, USA, did not show the transmission to the newborns (56). HTLV-II provirus was found in breast milk from HTLV-II-infected mothers (60), but there is no data available regarding the transmission to breastfed children. Meanwhile, a more recent study conducted among Kaiapos Indians in Brazil's North region indicates a vertical transmission rate of 45% in newborn children of HTLV-II-seropositive mothers (P. Novoa). HTLV-II can be transmitted sexually (61); the risk factor frequently reported among HTLV-II-infected North-American blood donors is the sexual contact with intravenal drug user (6,58). HTLV-II can be transmitted through transfusion of cellular products (platelets, red cells, and total blood) (31,32). The probability of transmission with hemácias seems to decrease with higher storage duration of the product (31). The high prevalence of HTLV-II among intravenal drug users is due to the sharing of needles or other paraphernalia for the injection, which includes the contaminated blood (62).

Related diseases

HTLV-II infection is not clearly related with any other type of disease. The virus was first isolated in two patients with hairy cells leukemia (2,63), but no evidence of HTLV-II infection was found in 21 additional patients with hairy cells leukemia (64). In a study, it has not been found rates more latas of lymphoproliferative diseases among Native-Americans from New Mexico, where HTLV-II is present (65). Rare cases of neurological diseases similar to HAM/TSP (66), mycosis fungoides (67), granular lymphocytes leukemia (68), were reported in people infected with the HTLV-II. Cases of skin bacterial infections and erythrodermatitis in people co-infected with the HTLV-II and HIV-1 (69) have been published.