At one time, up to half of IDUs commonly shared needles and syringes (Lyu et al. 1999) . A recent study indicated that following the SARS outbreak in Taiwan an increase in sharing of needles may have helped cause the rapid increase of infections among IDUs; they may have engaged in more of this risky sharing behaviour because of a perceived decrease in the drug supply during the outbreak (Lyu et al. 2008) .