Organ Transplantation

Risk from transplanted organs

The risk of being infected with West Nile virus from a transplanted organ is low.

The following can affect your chances of being infected with West Nile virus from a transplanted organ:

• Time of year. Infection risk increases during months when mosquitoes are most active (June through October).
• Number of West Nile virus disease (West Nile) cases in a year
• Where the organ donor lives
  

Testing organ donors

Previously, organ donors in the United States were not always tested for West Nile virus. As of June 2026, seasonal WNV testing from July 1 through October 31 is now required for all potential living and deceased solid organ donors.

Donation after infection

You can still be an organ donor if you have had West Nile in the past. A small number of patients have been infected with West Nile virus from transplanted organs. However, those organs came from donors who were recently infected with West Nile virus and still had virus in the blood or tissues at the time of donation.

Risk of severe illness

Organ transplant recipients are generally at higher risk of severe West Nile illness because they take medications that can weaken the immune system. Seventy-five percent of transplant recipients who become infected develop severe illness. This is much higher than the risk among most people who do not have weakened immune systems and are infected by mosquito bite (less than 1%).