The number of vCJD cases continues to decline, and it is believed that most cases to date are the result of consumption of BSE-infected beef. There were 161 recorded cases by the end of 2005, and the annual incidence has been steadily decreasing since 2000, with estimates for the total scale of the epidemic through this route now lie in the low hundreds.
However, concern has been raised that transmission could, in theory, occur directly from one person to another via routes such as blood transfusions and surgical operations, despite instruments being decontaminated routinely before being used. Scientists based at both the London School of Hygiene & Tropical Medicine and the National Creutzfeldt-Jakob Disease Surveillance Unit at Western General Hospital in Edinburgh decided to explore this possibility.
The results, published online today by the Journal of the Royal Society Interface, show that key factors determining the scale of any epidemic are the number of times a single instrument is re-used, combined with how infectious contaminated instruments are and how effective the cleaning is.
The authors begin by presenting data on the surgical procedures undertaken on vCJD patients prior to the onset of clinical symptoms which support the hypothesis that cases via this route are possible. They then apply a mathematical framework to assess the potential for self-sustaining epidemics via surgical procedures.
They conclude that further research is needed into how surgical instruments are used so as to reduce uncertainty and assess the potential risk of this transmission route.
They comment: 'Given the frequency of high- and medium-risk surgical procedures undertaken in the UK, a range of plausible scenarios suggest that surgical procedures could provide a potential route for a self-sustaining epidemic of vCJD. A first step to reducing the current uncertainty in the potential for self-sustaining transmission via surgery would be to survey the frequency with which different instruments are used, particularly those used on high-infectivity procedures. Also, tracking of surgical instruments should be improved, so that, at the very least, instruments are not re-used once the infection status of a patient is known'.
To interview the authors of the study or for copies of the paper, please contact the London School of Hygiene & Tropical Medicine's Press Office on 020 7927 2073.
Notes to Editors:
Factors determining the potential for onward transmission of vCJD via surgical instruments (doi:10.1098/rsif.2006.0142) by Tini Garske1, Hester JT Ward2, Paul Clarke1, Robert G Will2, Azra Ghani1.
1Department of Epidemiology and Population Heal th, London School of Hygiene & Tropical Medicine 2National Creutzfeldt-Jakob Disease Surveillance Unit, Western General Hospital, Edinburgh
Further information on the Journal of the Royal Society Interface can be found at: www.pubs.royalsoc.ac.uk/interface