id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-020756-d9f5fd7x	de Jong, Menno Douwe	Avian Influenza Viruses and Pandemic Influenza	2007		.txt	text/plain	15047	677	41	This is illustrated by the fact that during its evolution in humans, the NA of H2N2 viruses, which were of avian origin and therefore highly specific for hydrolization of α2,3-linked sialic acids, acquired high affinity for the human α2,6-linked sialic acids (Baum and Paulson, 1991) In addition to the surface glycoproteins, laboratory experiments with reassortant viruses suggest that the genes encoding internal proteins, such as M, NP, PB1 and PB2, may also play a role in determining the host range (Almond 1977; Scholtissek et al., 1978a; Snyder et al., 1987; Subbarao et al., 1993) . By reverse genetics experiments, it has been shown that a lysine residue at position 627 (Lys627) of PB2 seems essential for high virulence and systemic replication in mice of highly pathogenic influenza H5N1 viruses responsible for the outbreak among poultry and humans in Hong Kong in 1997 (H5N1/97) (Hatta et al., 2001) .	./cache/cord-020756-d9f5fd7x.txt	./txt/cord-020756-d9f5fd7x.txt