1. Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy.
2. Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy.
3. I.N.M.I “L. Spallanzani,” Rome, Italy.
4. Department of Experimental Medicine and Surgery, University of Tor Vergata, Rome, Italy.
5. Laboratory of Molecular Virology, Foundation Polyclinic Tor Vergata, Rome, Italy.
6. Theoretical Biology Divisions, Los Alamos National Laboratory, Los Alamos, New Mexico.