It has been drawn to the publisher's attention that this article \[[@B1]\] was inadvertently published with certain omissions. The authors apologize for the omissions in the published article.

The co-authors Nicolas Sluis-Cremer and Brian D. Herman, Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA have now been added as co-authors.

The following sentence has been added to the acknowledgements section: "The research in the N.S.--C laboratory was supported by a grant from the United States of America National Institutes of Health (GM068406)"
