The yield of temporary exclusion of blood donors, exposed to emerging infections abroad.

BACKGROUND AND OBJECTIVES: Emerging infections abroad pose a threat to the safety of blood, donated by travelling blood donors. In this study, the yield of donor deferral after travelling was evaluated, by comparing the estimated numbers of infected donors returning from various affected areas. METHODS: A deterministic model was applied to calculate the number of infected donors, returning from six areas affected by outbreaks: Greece - Macedonia (West Nile fever), Italy - Emilia Romagna (West Nile fever), Thailand (chikungunya), Latvia (hepatitis A), central Turkey (Sicilian sandfly fever) and Italy - Tuscany (Toscana sandfly fever). RESULTS: The estimated number of infections among returning blood donors was surprisingly low, ranging from 0·32 West Nile virus-infected donors per year returning from Macedonia (Greece) to approximately 0·005 infected donors per year returning respectively from Tuscany (sandfly fever), Latvia (hepatitis A) and central Turkey (sandfly fever). CONCLUSION: The yield of the temporary exclusion of blood donors travelling to a specific, affected area is low, but the continuous monitoring of emerging infections and the timely assessment of new threats are laborious and imperfect. Safety measures may be instituted after the greatest threat of a new outbreak has passed. A general deferral of travelling donors may be more appropriate than targeted measures. It can be argued that all donors who stayed outside their country or continent of residency should be deferred for 4 weeks.

The outcome of donor screening for human T-cell lymphotropic virus infection in The Netherlands.

BACKGROUND AND OBJECTIVES: Blood donor screening reduces the infectious hazards related to blood transfusion, but the range of agents to be screened for is debatable. In 1993, the screening of all blood donations for Human T-Cell Lymphotropic virus (HTLV) was introduced in The Netherlands. We analysed the outcome and costs of HTLV donor screening. METHODS: For the years 2001-2010, the number of HTLV infections among new and regular donors was used to estimate the prevented number of HTLV-infected donors in the donor pool and the amount of morbidity prevented among recipients. RESULTS: Human T-Cell Lymphotropic virus screening in The Netherlands detects per year on average 1·4 infected new donors and 0·5 infected regular donors. The prevalence among new donors is 30 times higher than the incidence among regular donors. Without HTLV screening, 14 HTLV-infected donors would be donating blood, causing 0·8 to 0·007 cases of HTLV disease per year. CONCLUSION: The lack of accurate estimators for infectivity and pathogenicity hampers the estimation of morbidity and mortality that HTLV-infected transfusions would cause. Leucodepletion may be as effective as HTLV donor screening; its effect on HTLV transmission should be studied.

The cellular basis of intrinsic sinus node recovery time.

STUDY OBJECTIVE: The aim was to investigate the mechanism of the intrinsic sinus node recovery time. DESIGN: The effect of 2 min periods of 20% and 50% overdrive on the electrical activity of fibres in the sinoatrial node was studied in isolated atria of rabbits under complete autonomic blockade (atropine 3 x 10(-6) M and propranolol 3 x 10(-7) M). EXPERIMENTAL MATERIAL: Rabbits (New Zealand white) of either sex up to 3 kg weight were used. MEASUREMENTS AND MAIN RESULTS: The first returning cycle after overdrive is prolonged not only by the time needed for retrograde plus antegrade conduction but also by a delay in impulse formation (overdrive suppression). During pacing, action potential duration, amplitude, maximum diastolic potential (only in primary pacemaker fibres), and diastolic depolarisation rate were all decreased. Action potential duration, amplitude and maximum diastolic potential returned to control value during the first cycle following a period of overdrive, but diastolic depolarisation remained depressed during many consecutive cycles. In primary pacemaker fibres, diastolic depolarisation appeared to be depressed throughout diastole. In latent pacemaker fibres diastolic depolarisation was depressed only in the second part of the diastole. CONCLUSIONS: Sinus node recovery time has two components: (1) a conduction component of both retrograde and antegrade conduction, and (2) a depression of the automaticity (= overdrive suppression), which is only due to a slowing of diastolic depolarisation.