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Introduction |
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Gibney and colleagues undertook a cross-sectional seroprevalence survey of HIV, hepatitis B, C and D among a group presumed to be at high risk (truck drivers), and assessed risk factors for hepatitis B infection. Their findings fit in well with what is currently known about these infections in Bangladesh and raise pertinent questions about the most effective methods for their prevention.
Results from sentinel surveillance show that Bangladesh currently appears to have a relatively low level of HIV, except among injecting drug users.2 The reported prevalence in sex workers, for example, is between 0 and 1.5%. Nonetheless, syphilis prevalence in the sentinel surveillance surveys, and the results of both cross-sectional3,4 and behavioural surveillance surveys5 lead to the conclusion that there is the potential for a more widespread and sustained epidemic in the country.
In the absence of an affordable and effective HIV vaccine, prevention campaigns must be designed to achieve maximum impact, often with limited financial and biomedical resources, and decisions have to be made about the extent of risk and vulnerability in different sections of the population. Experience from other countries (including Bangladesh's neighbouring country, India) suggests that people who are more mobile, such as truck drivers, may play a crucial role in the spread of HIV.6 The results published by Gibney et al. are consistent with those reported from truck drivers in Bangladesh's behavioural surveillance survey (first round, 19981999).4 In this latter survey truck drivers reported high levels of sexual mixing and low levels of protection: a mean of 11.3 sex partners in the past year; 14% had sex with both men and women; 44% had experience of group sex; and use of condoms was low with less than 20% using condoms at last paid or unpaid sex. For this reason, these and other high risk groups (e.g. sex workers and their clients, seafarers, injecting drug users) have been the targets of primary (and sometimes secondary) prevention activities in countries perceived to be in an early HIV epidemic scenariosuch as Bangladesh. This targeted approach is calculated to be highly cost-effective,7 and often goes hand-in-hand with more general campaigns to raise public awareness.
Whilst the world awaits the development of an HIV vaccine, prevention of hepatitis B is, in theory, already possible through the existence of a cheap and effective vaccine. The virus is chronically endemic in the countries of East and South-East Asia, and there is an increasing body of evidence documenting intermediate8 levels of infection in South Asian countries as well. Seroprevalence surveys among men and women in both Bangladesh and India have found evidence of exposure and chronic carriage rates similar to those reported by Gibney et al. Community-based surveys in Bangladesh have found carriage rates (presence of hepatitis B surface antigen) of 5.7% in studies of over 500 urban men and 9% in a similar number of rural men (ICDDR,B data, unpublished), with slightly lower rates reported among women in the same geographical areas.9
Why are carriage rates so high? In part this is a reflection of the age of prevention programmes in the countryimmunization activities are relatively new and not yet well established. It is also a reflection of the multiple transmission routes in a vulnerable population. Supporting Gibney's findings, other studies in India and Bangladesh have highlighted the possible roles of both sexual activity and non-sterile injection procedures in the transmission of hepatitis B in the adult population. Surveys among sex workers in Dhaka, for example, found that almost 10% were carrying hepatitis B surface antigen and 57% had markers of previous exposure.10 Similarly, there is a large body of evidence highlighting the risk of non-sterile injection practices and the transmission of the virus.1113
Given the contribution of the blood-borne hepatitis infections to the overall burden of communicable diseases in South Asia, what strategies can be adopted for their control? Gibney and colleagues highlight the importance of therapeutic injections, and we know from other studies that a large number of these injections are unnecessary for clinical care or disease control.14 A starting point for control should include a concerted research effort to understand the importance of parenteral administration from the recipients' viewpoint (why do people choose to have an injection rather than an oral course of treatment?). The next steps will involve interventions with both clients and providers to try and change prescribing practices through a reduction in the use of injections and an increase in their safety. The introduction of one-time-use-only needles and syringes may improve injection safety, but only if these are affordable for the majority of users.
Prevention of sexual transmission is undoubtedly important, but there is evidence suggesting that the relative importance of this mode versus other transmission routes may be low as most infections are acquired in childhood.15,16 Given this, the salience of universal vaccination increases,17 and the evidence presented by Gibney et al. confirms the importance of this intervention. The inclusion of hepatitis B into national immunization programmes has been a World Health Organization (WHO) recommended policy since 1992,7 and has been shown to be a highly cost-effective strategy in India.18 Despite such evidence, India is only this coming fiscal year beginning a vaccination strategy in 15 pilot Districts (WHO office, Delhi, personal communication). In Bangladesh, planning for a pilot phase is still underway and the vaccine is not yet included in the childhood vaccination strategy (Dr K Zaman, ICDDR,B personal communication). Along with the plans for incorporating hepatitis B immunization into the expanded programme of (childhood) immunization, Gibney et al.'s work highlights the importance of prevention strategies in the adult populationto reduce both iatrogenic and sexual transmission.
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Notes |
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References |
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