Since it was first identified in New York City in 1999, West Nile virus has become endemic across the United States. The virus has caused an estimated 780,000 illnesses, over 16,000 documented neuroinvasive cases and more than 1,500 deaths.
Here is Dr. Lyle Peterson from the Centers for Disease Control:
“Last year in 2012 there was a huge increase in the number of cases. It was the largest outbreak we have experienced since 2003. We are going to continue to experience periodic large outbreaks which clearly would indicate a great risk for transfusion medicine had not screening been implemented.”
In order to guide future prevention efforts, researchers assessed the epidemiologic, meteorologic, and geospatial features of the 2012 epidemic in Dallas, Texas. In a study published in JAMA, researchers found that large epidemics were often preceded by warm winters and that epidemics revisit the same geographical areas. In addition, they found an important marker of the virus, which may be used to predict outbreaks.
Here is Dr. Robert Haley, who led the study:
“Our study found that there’s a statistic called the vector index calculated from weekly mosquito infection surveillance data the health department has helped collect. And this vector index can predict West Nile epidemics, weeks before the human cases come to attention.”
In addition, Dr. Haley noted that infected blood donors could be an additional signal for an oncoming epidemic:
“We started seeing positive blood donors just at the same time the vector index started jumping up. Suggesting timely reporting from regional blood banks might also be a very useful alert for early warning of epidemics.”
Since 2003, the United States blood supply has been routinely screened for West Nile virus; as a result, transfusion-associated infections are rare. Screening for all possible threats to the blood supply, however, can be costly.
Dr. Peterson added:
“The idea of pathogen inactivation is a very compelling one because of all these potential threats of blood supply, if we keep implementing screening measures. It is almost like putting your finger in a dyke to stop a flood.”
We’ll be back with another edition of Transfusion News on September 15th. Until then, thanks for joining us.
4. US Department of Health and Human Services. Centers for Disease Control and Prevention. National Center for Emerging and Zoonotic Infectious Diseases. Division of Vector-Borne Diseases. West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control. June 14, 2013. Accessed online July 31, 2013. http://www.cdc.gov/westnile/resources/pdfs/wnvGuidelines.pdf.