1. Department of Science and Mathematics, Abraham Baldwin Agricultural College, Tifton, GA 31793, USA
2. Department of Mathematics, Morgan State University, Baltimore, Maryland 21252, USA
3. Department of Mathematics, San Diego State University, San Diego, California 92182, USA
4. Computational Science Research Center, San Diego State University, San Diego, California 92182, USA
5. Viral Information Institute, San Diego State University, San Diego, California 92182, USA