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Fig. 3. Postulated mode of transmission of HCV from source to index patient through contaminated reusable tube holder. (A) The double-end needle is fitted onto the tube holder by a screw-on motion, with rubber sleeve capping sleeved-needle being ‘inside’ the tube holder. The skin-needle is then inserted into the patient’s vein for blood collection. The vacuum-specimen tube is plunged into the sleeved-needle by insertion into the tube holder. Blood is drawn automatically by negative pressure into the vacuum tube. (B) From above to below, blood collection from known HCV carrier. Upon removal of the vacuum-specimen tube, a rapid pressure change leads to a trace amount of blood being splashed onto the inside of the holder and the tip of the sleeve capping the sleeved-needle. While the double-end needle is being removed, its blood-stained sleeved tip contaminates the path along which the next clean double-end needle is inserted. The sleeved-needle of the new double-end needle is now fitted onto the HCV- contaminated holder and its sleeve tip gets contaminated by HCV-positive blood along the path of insertion. (C) The skin-needle is then inserted into the vein of the index victim patient. While the stopper of the new vacuum-specimen tube is plunged onto the sleeved-needle with compression of the rubber sleeve, the HCV-positive blood on the tip of the sleeve is being smeared onto the exposed metal surface of the sleeved-needle. (D) On removal of the vacuum-specimen tube, the rubber sleeve cap will recoil to its original position covering the sleeved-needle. The venous blood of the index patient under pressure goes into the potential space between the rubber sleeve and the sleeved-needle. (E) Upon release of the tourniquet, the relatively lower venous pressure above the tourniquet sucks the HCV-contaminated blood collected in the space between the rubber sleeve and the sleeved-needle through the double-end needle back into the patient’s vein.


capping will be easily contaminated along the path of insertion, especially when the double-end needle is inserted at a slight angle. When another vacuum-specimen tube is inserted through the tube holder, HCV particles contaminating the tip of the new sleeve will be smeared onto the sleeved-needle by the stopper of the vacuum-specimen tube while compressing the rubber sleeve, thus exposing the sleeved-needle. On withdrawal of the vacuum- specimen tube, the rubber sleeve capping the sleeved-needle will recoil and regain its original position, and the space between the rubber sleeve and the HCV-contaminated sleeved-needle will be filled by venous blood under positive pressure from the tourniquet-treated arm. Once the tourniquet is released, the blood in the vein below the tourniquet will flow back to the heart while sucking the HCV-contaminated blood collected in the space between the sleeve and the sleeved-needle back into the patient’s


vein. Our in vivo experiment confirmed that there is a significant drop in venous pressure of at least 11mmHg during the release of a tourniquet, regardless of sitting or lying position. The envir- onmental stability of HCV facilitates transmission via this route. The HCV remains infective for up to 6 weeks after drying on inanimate surfaces at room temperature,28 and HCV infectivity was detectable for up to 5 months in a liquid environment at lower temperatures.29 Thermostability tests showed that different HCV genotypes possess comparable environmental stability.30 Also, HCV RNA viral loads showed no significant differences after 10 freeze–thaw cycles in serum and plasma samples.31 Therefore, it is not surprising that HCV RNA was detected inside the reusable tube holder in the ward after 3 months. Our radioisotope experiment illustrated that the HCV inocu- lum contaminating the sleeve tip capping the sleeved-needle


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