id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-048466-fj9l8che	Bragstad, Karoline	The evolution of human influenza A viruses from 1999 to 2006: A complete genome study	2008-03-07		.txt	text/plain	5357	322	53	BACKGROUND: Knowledge about the complete genome constellation of seasonal influenza A viruses from different countries is valuable for monitoring and understanding of the evolution and migration of strains. The influenza virus evades host immunity by accumulation of point mutations (drift) in the major surface glycoproteins, haemagglutinin (HA) and neuraminidase (NA) or by reassortment of segments from different viruses co-infecting the same cell leading to a new stain with a HA (and NA) not seen in the population before (shift). The A/Fujian/411/02(H3N2)-like clinical Danish viruses had several substitutions in HA at sites that might influence the virus' capability for egg growth [10, 37] . Substitutions at antigenic site B and the predicted N-glycosylation at position 144 in HA antigenic site A together with a stronger NA might have contributed to the increased infectivity of the reassorted Fujian-like viruses of the 2003-2004 season, causing an epidemic in Denmark. Positive selection on the H3 hemagglutinin gene of human influenza virus A	./cache/cord-048466-fj9l8che.txt	./txt/cord-048466-fj9l8che.txt