In regions where West Nile Virus is prevalent, blood banks may screen for the virus to prevent its transmission through blood transfusions.

West Nile Virus (WNV) is a mosquito-borne virus that can infect humans and animals.  West Nile Virus is primarily transmitted to humans through the bite of infected mosquitoes. Mosquitoes become infected when they feed on infected birds, which serve as the primary reservoir of the virus. Many people who are infected with West Nile Virus do not develop any symptoms, while others may experience mild to moderate symptoms, including fever, headache, body aches, joint pain, vomiting, diarrhea, or rash.

According to American red cross -Following the introduction of blood donation screening in 2003 through the end of 2018, there have been 15 cases of documented WNV-transfusion transmission from screened blood; all are believed to be due to donations having very low levels of virus. This translates to a risk of about 1 per 84 million donations for the Red Cross overall (or 1 per 35 million during the summer transmission season).

Image credit: Photo by Charlie-Helen Robinson: https://www.pexels.com/photo/blood-samples-in-test-tubes-6622519/ (cc by 0)