US FDA scientist sees challenges in H1N1 vaccine. Manufacturers may run into challenges in efforts to produce a vaccine against the new H1N1 flu strain depending on how the virus acts, the U.S. Food and Drug Administration's chief scientist told Reuters on Wednesday. [News Source]

Swine flu ancestors may protect elderly, experts say. Swine flu evolved from human viruses circulating in pigs for more than a decade, a finding that may explain why people in their 30s and 40s are getting sicker than the elderly in the U.S. and Mexico, scientists said today. [News Source]

Flu from animals an ongoing threat – reports. The first batch of formal reports looking at the current outbreak of a new kind of swine flu virus shows it is a Frankenstein-like mixture of viruses, researchers reported on Thursday. [News Source]

Devilish dilemmas surround pandemic flu vaccine. If and when a pandemic of H1N1 swine flu hits, vaccines might be the world's best hope for softening the blow. But major uncertainties cloud the prospects for vaccines against the new strain. [News Source]

Top flu expert warns of a swine flu-bird flu mix (AP via Yahoo! News) Bird flu kills more than 60 percent of its human victims, but doesn't easily pass from person to person. Swine flu can be spread with a sneeze or handshake, but kills only a small fraction of the people it infects. [News Source]

Top flu expert warns of a swine flu-bird flu mix (Boston Herald) MEXICO CITY - Bird flu kills more than 60 percent of its human victims, but doesn't easily pass from person to person. Swine flu can be spread with a sneeze or handshake,... [News Source]

Expert Warns Of Swine Flu-Bird Flu Mix (WSB-TV 2 Atlanta) Epidemiologists worry that bird flu's high mortality rate and swine flu's rapid spread could make for an extremely dangerous flu hybrid. [News Source]

Top flu expert warns of a swine flu-bird flu mix (KWQC-TV 6 Davenport) MEXICO CITY (AP) - Some top experts are worried that a mix of old and new flu could become lethal -- if it happens. Bird flu kills more than 60% of its human victims, but doesn't easily pass from person to person. [News Source]

Top flu expert warns of a swine flu-bird flu mix (AP via Yahoo! Asia News) Bird flu kills more than 60 percent of its human victims, but doesn't easily pass from person to person. [News Source]