Background: The recent spread of the Zika virus to the Americas and the recognition that it can cause severe disease in the developing fetus has prompted the adoption of measures to mitigate the risk that this virus might pose to transfusion safety. In nonendemic countries, the risk to transfusion results from donors traveling to an endemic region. Canada implemented a 21-day temporary deferral for prospective donors who traveled to such regions. We present the rationale for this policy, including a quantitative risk assessment supported by a Monte Carlo simulation.
Study design and methods: The model considered the following parameters, each with specified values and ranges: the probability that a donor recently returned from a Zika-endemic region, the duration of travel to this region, the daily risk of acquiring Zika while in an endemic region, and the incubation and viremic periods. We ran the simulation 20 times, each with 10 million iterations.
Results: In the absence of any travel deferral, 32 donors (range, 20-46 donors) would be able to donate while still being at risk of transmitting Zika, corresponding to a rate of 1:312,500 (range, 1:217,000 to 1:500,000). None of these donors would be viremic beyond 21 days after returning from their travel, with a risk estimated at less than 1:200,000,000.
Conclusions: A 21-day temporary travel deferral offers an extremely wide margin of safety for the possible transmission of Zika by a donation obtained from someone who recently returned from a country where the virus is circulating.
© 2017 AABB.