Zika virus and safe blood supply: Questions and answers
Can Zika virus be transmitted through donated blood?
Zika virus may present a risk to blood safety. Currently there is a limited knowledge of Zika virus and the ways it can be transmitted. The majority of cases are transmitted to people through the bite of an infected mosquito, Aedes mosquitos. Until more is known about other means of transmission, precautions should be taken to ensure the supply of blood is safe.
- Zika virus has been detected in blood donors in affected areas.
- Transmission of related flaviviruses (dengue and West Nile virus) by blood transfusion has been documented, and thus transmission of Zika virus is possible.
- Recently 2 probable cases of Zika virus transmission by blood transfusion have been reported from Campinas, Brazil.
What precautions should be taken to ensure that the blood supply is safe in countries where Zika infection is occurring?
Ideally the blood supply during a regional outbreak of Zika should be maintained by increasing blood collections in non-affected areas. In non-affected areas, consideration may be given to defer potential donors who have recently visited areas with ongoing transmission of Zika virus infection for 28 days after their departure from these areas.
What about blood donations in areas affected by Zika?
Blood collection may need to continue in affected areas to meet needs for blood and its components. This may be necessary when an outbreak is affecting a large swathe of a country or when it is not possible to get blood from regions where Zika is not circulating.
What measures may be considered for reducing the risk of Zika virus through blood transfusion in areas with active Zika virus transmission?
- Temporary exclusion of donors with a recent clinical history consistent with Zika virus disease, such as a combination of fever or rash with pinkeye, muscle aches, headache or malaise.
- Temporary exclusion of donors for whom laboratory test results show they may recently have been infected.
- Donors with clinical history consistent with Zika virus disease or a recent history of Zika virus infection should be deferred for a period not less than 28 days following the full resolution of symptoms.
- Similarly, sex partners of men with confirmed or suspected Zika virus infection in the last 3 months should be deferred for at least 28 days after their last sexual contact.
- People who have already donated must be encouraged to report to the blood transfusion service if they subsequently get symptoms of Zika virus infection, or if they are diagnosed with recent Zika virus infection within 14 days after blood donation.
- Blood components of appropriate shelf life (e.g. red blood cells) may be quarantined for a period of 7–14 days and released following confirmation from the donor that he or she has not experienced symptoms consistent with the acute phase of Zika virus infection. For platelets, which have a shorter shelf life, a 3-day quarantine period may be considered.
- Countries with many visitors to affected countries may need to assess the impact of deferral on blood supply availability and weigh the risks against the benefits of restricting donations.
How could blood donations be tested for the presence of Zika virus?
Where possible, blood donations may be tested for the presence of Zika virus by appropriate tests. Likely, pathogen reduction technology (PRT) may be implemented for plasma and platelets.
In some cases, the selective testing for the presence of the virus in blood donors returning from affected countries may be considered as an alternative to deferral.
Should countries prepare that only have the Aedes mosquitoes but where the Zika virus has not been found?
WHO recommends that countries where the mosquito that carries Zika exists, yet the virus itself has not been found, consider preparing a plan to ensure the availability of a safe and sufficient supply of blood should an outbreak occur.