28/29 April 2020
End of July, the FDA/CBER published a short summary about the scientific work of FDA researchers who were concerned with the genetic background and genetic changes of the mosquito-borne West Nile Virus (WNV). This virus, normally hosted by birds and mosquitos, can be occasionally transmitted by the mosquitos to humans and causes symptoms in 20% of these cases. As many other viruses too, the WNV underlies permanent genetic changes and the study of the FDA scientists highlights the need for continuously tracking and identifying new genetic variants of WNV in order to protect public health from the annual outbreak of this disease, for which there are no specific therapies or vaccines.
It is important, because it is known, that WNV can be transmitted by transfusion of blood and blood components and by organ transplantation. Therefore some guidelines and guidance documents were published since WNV emerged in the United States in 1999 - as examples:
But if the virus will underlie genetic changes, it is a valid question, whether tests used to diagnose infection and screen blood donors, as well as vaccines and drug therapies may not perform as well against newer genetic variants of WNV.
The scientists tracked now samples obtained from 1999 - 2012 and they detected several codons in the WNV genetic material that had undergone mutations that remained in a variety of virus populations over the years.
FDA summarized: "The study’s findings also suggest that these genetically similar variants may be a new strain of WNV emerging in the United States. They also suggest that by studying genetic changes in the virus, scientists can obtain important insights into the virus’s ability to spread, clues for designing anti-WNV vaccines, drug treatments, and reliable tests for screening blood donors for this virus."
For more details, please see the FDA publication: Tracking genetic changes in West Nile Virus that could affect its spread and the ability of blood donor screening tests, future treatments, and vaccines to work effectively or the publication Genetic Variability of West Nile Virus in U.S. Blood Donors from the 2012 Epidemic Season by Andriyan Grinev , Caren Chancey, Evgeniya Volkova, Germán Añez, Daniel A. R. Heisey, Valerie Winkelman, Gregory A. Foster, Phillip Williamson, Susan L. Stramer, Maria Rios, Published: May 16, 2016