“…Viral genes encoding outer capsid or envelope proteins have been the most frequently implicated determinants of pathogenicity (e.g., reovirus Si gene [38,42], Sindbis virus El and/or E2 proteins [20,22], lymphocytic choriomeningitis virus S gene [29], mouse hepatitis virus type 4 E2 protein [5], JHM murine coronavirus E2 protein [10], rabies virus glycoprotein [6,7,23,33], mumps virus hemagglutinin/neuraminidase protein [19], influenza virus hemagglutinin protein [2], and poliovirus VP1 protein [21]). However, genes encoding viral proteins with polymerase function (e.g., lymphocytic choriomeningitis L gene [28] and influenza virus PB1, PB2, PA, and NP proteins [31]) as well as noncoding regions of the genome (poliovirus 5' noncoding region [9,17]) have also been indicated as determinants of virulence.…”