Epidemiological Aspects and World Distribution of HTLV-1 Infection

CNRS, URA3015 Paris, France.
Frontiers in Microbiology (Impact Factor: 3.94). 11/2012; 3:388. DOI: 10.3389/fmicb.2012.00388
Source: PubMed

ABSTRACT The human T-cell leukemia virus type 1 (HTLV-1), identified as the first human oncogenic retrovirus 30 years ago, is not an ubiquitous virus. HTLV-1 is present throughout the world, with clusters of high endemicity located often nearby areas where the virus is nearly absent. The main HTLV-1 highly endemic regions are the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area and foci in Middle East and Australo-Melanesia. The origin of this puzzling geographical or rather ethnic repartition is probably linked to a founder effect in some groups with the persistence of a high viral transmission rate. Despite different socio-economic and cultural environments, the HTLV-1 prevalence increases gradually with age, especially among women in all highly endemic areas. The three modes of HTLV-1 transmission are mother to child, sexual transmission and transmission with contaminated blood products. Twenty years ago, de Thé and Bomford estimated the total number of HTLV-1 carriers to be 10-20 millions people. At that time, large regions had not been investigated, few population-based studies were available and the assays used for HTLV-1 serology were not enough specific. Despite the fact that there is still a lot of data lacking in large areas of the world and that most of the HTLV-1 studies concern only blood donors, pregnant women or different selected patients or high-risk groups, we shall try based on the most recent data, to revisit the world distribution and the estimates of the number of HTLV-1 infected persons. Our best estimates range from 5-10 millions HTLV-1 infected individuals. However, these results were based on approximately 1.5 billion of individuals originating from known endemic areas with reliable available epidemiological data. Correct estimates in other highly populated regions such as China, India, the Maghreb and East Africa is currently not possible, thus, the current number of HTLV-1 carriers is very probably much higher.

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Available from: Olivier Cassar, Aug 27, 2015
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    • "However, most seropositive individuals are asymptomatic and less than 2% develop a neurological disease, mainly HAM/ TSP or ATL [Shoeibi et al., 2013]. Worldwide, approximately 15–20 million persons are estimated to be infected with HTLV-I [Proietti et al., 2005; Gessain and Cassar, 2012]. HTLV-I infection is endemic in certain geographical regions, such as; Iran, Japan, the Caribbean Islands, parts of Africa, and Central and South America, with a prevalence rate of more than 1% in the general population [Blattner et al., 1982; Saxinger et al., 1984; Reeves et al., 1988; Yamaguchi, 1994; Farid et al., 1995; Cesaire et al., 1999; Shindo et al., 2002]. "
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    • "The two viruses also differ in their geographical distribution. HTLV-1 is endemic in Japan, sub-Saharan Africa, South America, and the Caribbean (Gessain and Cassar, 2012), whereas HTLV-2 is prevalent among the indigenous populations in Africa and the Indian-American tribes in Central and South America as well as among drug users in Europe and North America (Zella et al., 1990; Roucoux and Murphy, 2004). Although their receptor usage allows HTLV-1 and HTLV-2 to be quite promiscuous for different cell types in vitro, they exhibit distinct cellular tropisms in vivo: HTLV-1 is mainly found in CD4+ T lymphocytes, whereas CD8+ T cells are the preferred target for HTLV-2 (Ijichi et al., 1992). "
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