1. Department of Genetics and Microbiology, University of Pavia, Pavia, Italy.
2. Laboratory of Virology and Microbiology, Fondazione IRCCS San Matteo, University of Pavia, Pavia, Italy.
3. DiSCAFF, Università del Piemonte Orientale, Novara, Italy.
4. Department of Evolutionary Biology, University of Florence, Firenze, Italy.