Epidemiology - HTLV

Analysis of eight years of surveillance of human T cell lymphotropic virus (HTLV) infections in England and Wales by the Health Protection Agency's Centre for Infections have shown that infections remain rare in the UK, although relatively higher risk is borne by Caribbean and African ethnic groups. Annual number of diagnoses remains fewer than the peak of 102 cases reported in 2003, when testing of blood donations was introduced.

Surveillance of HTLV, a retroviral infection, began (in England and Wales) in the late 1980s with laboratories reporting all new diagnoses. Enhanced surveillance began in 2002 with the routine follow-up of all laboratory reports with clinician reports. In August 2002 the National Health Service Blood and Transplant (NHSBT) began testing all blood donations in England and Wales for HTLV, with reports of any infections identified being passed to the enhanced National HTLV Surveillance system.

HTLV types I and II are transmissible through breast feeding, sexual contact, blood transfusion, and injecting drug use. HTLV-I is endemic in the Caribbean, Japan, South America and parts of Africa, with HTLV-II found among some native American groups and injecting drug users. An infected individual's lifetime risk of developing symptomatic disease is low (less than 5%) and the spectrum of clinical illness associated with infection is not fully understood. HTLV-I infection may cause adult T cell lymphoma (ATLL), HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) and other inflammatory conditions. There is some evidence that HTLV-II infection is also associated with neurological and lymphoproliferative disorders.

New diagnoses of HTLV 2002-2009

With the initiation of enhanced HTLV surveillance in 2002 more detailed epidemiological information is available for new HTLV diagnoses since 2002.

Between 2002 and 2009, 699 new diagnoses of HTLV infection in England and Wales were reported to the HPA Centre for Infections. There were 88 in 2002, 102 in 2003, 89 in 2004, 75 in 2005, 94 in 2006, 75 in 2007, 78 in 2008 and 98 in 2009. There were 60 deaths during this period in individuals who have been diagnosed with HTLV.

Among new HTLV diagnoses between 2002 and 2009, 35% (242/695), were men and 65% (453/695) were women. Sex was unreported for 4 individuals. Over this period, median age at diagnosis was 52 years for both men and women. The median age at diagnosis among men has decreased from 60 years in 2002 to 52 years in 2009, whilst among women the median age at diagnosis has increased from 48 years in 2002 to 55 years in 2009.

For 74% (520/699) of new diagnoses between 2002 and 2009, a clinician report or report from the National Health Service Blood and Transplant (NHSBT) was completed, containing information such as probable route and country of infection, reason for test and symptoms at diagnosis.

For those individuals with a clinician/NHSBT report and where ethnicity was reported (91% [472/520]), 61% (287/472) were black Caribbean, 23% (108/472) white, 8.5% (40/472) black African and 7.8% (37/472) of other ethnicity (Graph 2). Probable route of infection was reported for 67% (347/520) of individuals with a clinician/NHSBT report, of whom 27% (94/347) were probably infected through heterosexual intercourse, 24%(82/347) through mother to child transmission, 40% (138/347) through either heterosexual intercourse or mother to child transmission, 5.5% (19/347) through blood transfusion and 4.0% (14/347) through other routes including sex between men, injecting drug use and other blood contact.

Probable country of infection was reported for 52% (270/520) of individuals with a clinician/NHSBT report between 2002 and 2009. Of these, 43% (117/270) were infected in Latin America and the Caribbean, 42% (114/270) in the UK, 7.4% (20/270) in Africa, 3.7% (10/270) in Asia and 3.3% (9/270) in other regions (Graph 4).

Where test reason was reported (93% [482/520]), 47% (228/482) were tested after experiencing HTLV related symptoms and 34% (166/482) of individuals were tested as blood donors. Information on symptoms was reported for 98% (507/520) individuals with clinician/NHSBT reports, of whom 48% (241/507) were asymptomatic, 19% (97/507) had ATLL and 13% (67/507) had HAM/TSP. 6.3% (32/507) reported other HTLV-related symptoms, 8.7% (44/507) with other neurology\malignancies and 5.1% (26/507) of individuals reported non-HTLV symptoms.

Rates of HTLV infection in England and Wales (based on ONS 2007 population data estimates) continue to be much higher among black Caribbeans at 48/100,000 population, compared to 5.4 and 0.2/100,000 in persons of black-African and white ethnicity, respectively. The increase in cases since 2002 is due to anti-HTLV testing of blood donations. In 2009 the frequency of HTLV infection in blood donations in England and Wales in new donors is about 7.9 per 100,000 donations and for repeat donors 0.1 per 100,000 donations.

While most infections diagnosed are directly associated with travel to, or contact with those travelling to, the Caribbean, two in five diagnosed infections were probably acquired in the UK.

There are now three designated sites across England and Wales (London, Birmingham and Manchester) providing specialist investigation, treatment and contact screening services for infected individuals and their families. Additional strategies for the prevention of HTLV transmission, including screening of donated organs and donated breast milk, are under investigation.

England and Wales HTLV slides: HTLV Slide set 2002-2009 (PowerPoint Presentation, 248 KB)

Epidemiology - HTLV

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