Methods
Surveillance of new laboratory diagnoses of HTLV infection in E&W began in the late 1980s [3]. In 2002, surveillance was enhanced by the collection of further epidemiological information through a clinical reporting scheme, described in full elsewhere [4]. This coincided with the introduction of the national, routine testing of all blood donations for anti-HTLV by the UK Blood Services in August 2002 [4]. Reports of any HTLV infections diagnosed by the blood service in E&W are included in the routine surveillance scheme.

Probable route and country of infection are collected on clinical HTLV reports. The clinician indicates through which route the patient is most likely to have been infected through, and in which country. Where it is not clear, more than one route or country can be indicated. For those infected through heterosexual intercourse, information on their sexual partner is sought (e.g. had the partner injected drugs or has the partner had heterosexual intercourse in the Caribbean).

Surveillance findings from 2002 have previously been published [4]. Here, we present data from the surveillance system for 2002, 2003 and 2004; based on reports made to the scheme by the end of May 2005. The surveillance system coverage is likely to be near complete for laboratory-confirmed HTLV diagnoses made in E&W as most confirmatory testing for HTLV is undertaken at either at the Health Protection Agency Centre for Infections or the Health Protection Agency laboratory at King’s College hospital, from which routine laboratory reports are sent. In 2004, the laboratory at the Centre for Infections performed approximately 1,500 HTLV tests. Clinical reports are sent out for completion for every HTLV positive laboratory report received.

Results
Between 2002 and 2004, 273 reports of new HTLV diagnoses were made in E&W; 88 in 2002, 101 in 2003 and 84 in 2004. Two hundred and fifty one (93%) were HTLV-I infections, 13 HTLV-II, one a HTLV-I&II co-infection and for eight HTLV type was as yet undetermined. Of the 273 people diagnosed with HTLV between 2002 and 2004, 102 (37%) were men (four HTLV-II), 169 (62%) women (nine HTLV-II) and gender was not reported for the remaining two (one HTLV-II). The proportion of diagnoses among women increased over time: in 2002 57% of HTLV diagnoses were among women, by 2004, 69% [TABLE]. Median age at diagnosis was 54 years for men and 50 years for women.

The majority (67%) of reports were about individuals diagnosed or receiving care in London [FIGURE 1]. Elsewhere in E&W, the largest numbers of reports were about HTLV-infected individuals diagnosed/cared for in the West Midlands region of England.

At the time of writing, a clinical report (collecting more detailed epidemiological information), had been made for 212 (78%) individuals. The proportion of clinical reports made for individuals by year of diagnosis is as follows: in 2004 (75% [63/84]), in 2003 (83% [84/101]) and in 2002 (74% [65/88]). Further clinical reports for diagnoses made in 2004 are expected during 2005.

Where ethnicity was reported (199), 116 (58%) individuals were black Caribbean, 57 (29%) white (10 HTLV-II), 15 black African (one HTLV-II) and 11 of other ethnicity. The rate of HTLV diagnosis was therefore 20.5 per 100,000 among black Caribbeans living in E&W between 2002 and 2004, compared to 3.1 per 100,000 among black Africans and 0.1 per 100,000 among the white population [5]. The probable route of infection was reported for 147 individuals: 39 (27%) were probably infected through heterosexual intercourse (four HTLV-II), 40 (27%) through mother to infant transmission, 49 (33%) through either route, 14 through blood transfusion (two HTLV-II) and five through other routes (two HTLV-II) [FIGURE 2]. Where the probable country of infection was reported (146), 66 (45%) individuals were probably infected in the Caribbean (35 in Jamaica), 59 (40%) in the UK (four HTLV-II), 12 in Africa (seven in West Africa) (one HTLV-II), four in the Middle East, two in Asia and three elsewhere (one HTLV-II).

There were 42 individuals infected through either heterosexual intercourse or mother to child transmission within the UK, of whom four were known to have had a ‘high risk’ sexual partner (e.g. injecting drug user); 19 a partner or parent infected in the Caribbean, two a partner or parent infected in the UK and one, a partner or parent infected in Africa.

Where reason for testing was reported (208), 81 (39%) individuals had been tested because of symptoms (one HTLV-II), 82 (39%) as blood donors (eight HTLV-II), 13 (6%) had a HTLV-infected positive sexual partner, 13 (6%) had a HTLV-infected blood relative and 19 (9%) for other reasons (two HTLV-II). The reason stated changed over time [FIGURE 3]. There were larger numbers of individuals diagnosed through the screening of blood donors during 2002 (n=32) and 2003 (n=35) than in 2004 (n=15).

Clinical presentation at diagnosis was reported for 192 individuals, of whom 93 (48%) were asymptomatic (seven HTLV-II), 45 (23%) had ATLL, 14 (7%) had HAM/TSP and 40 (21%) had other symptoms (three HTLV-II) [FIGURE 4]. Where ATLL type was reported (n=36), 19 (53%) had a lymphoma, 11 (31%) acute ATLL, four chronic ATLL and two smouldering ATLL. Of all the individuals diagnosed between 2002 and 2004 in E&W, 14 are known to have died (one HTLV-II).

Discussion
An appreciable number of HTLV infections continue to be diagnosed within E&W each year. The introduction of anti-HTLV testing of blood donations increased the number of new HTLV diagnoses in 2002 and 2003. However, by 2004 low numbers of infected blood donors were identified - most donors had already been tested, with those found positive excluded from further donation and referred to specialist centres for appropriate care. Overall, the rate of HTLV infection in blood donations E&W between August 2002 and December 2004 for new donors was 5.1 per 100,000 donations and for repeat donors, 0.9 per 100,000 donations [6].

The majority of HTLV diagnoses were among those of black Caribbean ethnicity, with HTLV diagnoses rates highlighting that in E&W, the black Caribbean population is disproportionately affected by HTLV infection. Infections were thought to have been mainly acquired through heterosexual intercourse and/or mother to child transmission, both within the Caribbean and the UK. In the main, those infected in the UK had a partner or parent from an endemic area. Data illustrate therefore, that while HTLV infection in E&W is mainly found among those originating from endemic areas there is also transmission of the infection in E&W itself. The geographical distribution of diagnosed HTLV infection in E&W reflects both the distribution of the black Caribbean population, which is focussed in London (60%) and the West Midlands (14%) [7], and also the location of specialist HTLV centres in London and Birmingham.

A clinical report containing more detailed epidemiological and clinical information had not yet been received for 21 (25%) individuals diagnosed in 2004. More outstanding clinical reports are expected over the coming months. It is important to bear this in mind when interpreting trends. For a relatively large proportion of individuals for whom a clinical report was made, the probable route and country of was not known (~30%), highlighting difficulties in assigning these variables for infections acquired many years previously, particularly in clinical settings where sexual histories are not collected routinely (as they would be for example, in GU medicine). In addition, probable route of infection was not known for those with only a laboratory report. Such data incompleteness may bias conclusions from routine surveillance data. In this case, proportionally more of those diagnosed with symptoms or with no reason for test did not have a probable route of infection reported compared to those diagnosed as blood donors, a blood relative or because of a positive partner, as well as older individuals and those with no reported ethnicity. Finally, it is important to remember that not all of those living with HTLV infection in E&W will be diagnosed and there will be biases in ascertaining HTLV infections within the population. For example, all blood donations are tested for HTLV, and people with HTLV-associated symptoms or HTLV-infected relatives or partners are more likely to be tested than those with no symptoms or contacts.

In conclusion, while HTLV infections continue to be diagnosed in E&W, the number of diagnoses in any given year seems to have peaked in 2003 with the identification of HTLV-infected blood donors, when considering trends since 1987 [3]. While there are now three designated sites across E&W (London, Birmingham and Manchester) providing specialist investigation, therapy and contact screening services for those infected and their families, the prevention of HTLV transmission, for example through screening of pregnant women for HTLV infection and contact tracing, is limited.

Acknowledgements
We gratefully acknowledge the contribution of all of those who have reported to the HTLV surveillance system over the years, and support of Dr Barry Evans (Health Protection Agency Centre for Infections).