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How Lethal Is H5N1?

Is This Virus Series a Danger to Humans?

MARCH 6, 2012—Baltimore, MD—In an article published today, researchers at the Center for Biosecurity of UPMC assess the evidence regarding wild-type H5N1 and its lethality in humans. The article, “Is H5N1 Really Highly Lethal?,” was posted ahead of print on the website of the journal Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science.

Recently, there has been considerable debate among scientists and public health experts about research on genetically modified H5N1 avian influenza viruses—viruses that are highly lethal to birds and spread easily from bird-to-bird, but so far have not been readily transmissible among people. One of the issues that has arisen in this debate regards the lethality of wild-type H5N1 in humans.

The authors review the available evidence: the distinctions between different clades of H5N1, the clinical series of human H5N1 cases, and the seroepidemiological and laboratory studies. They conclude that the preponderance of evidence argues that H5N1 virus is indeed highly lethal in humans compared to other influenza viruses.

Author Eric Toner said, “Our review of the evidence underscores what so many experts have been saying for years: Wild-type H5N1 is a very dangerous virus. We are quite fortunate it has not yet become contagious between humans.”

The article, titled “Is H5N1 Really Highly Lethal?,” by Eric S. Toner and Amesh A. Adalja, appears online ahead of print in the current issue of Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science, a peer-reviewed journal published by Mary Ann Liebert, Inc. ( The article is available free online at


Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science, published quarterly in print and online, covers topics such as bioscience, medical and public health preparedness and response, infrastructure and institutions, international collaborations, agroterror/food safety, infectious disease surveillance, and citizen response and responsibility in all matters related to national and international biosecurity. It provides an international forum for debate and exploration of the many key strategic, scientific, and operational issues posed by biological weapons, bioterrorism, and other major health-related events.

The Center for Biosecurity is an independent, nonprofit organization of the University of Pittsburgh Medical Center (UPMC) whose mission is to strengthen national security by reducing the risks posed by biological attacks, epidemics, and other destabilizing events, and to improve the nation’s resilience in the face of such events.



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