"Two new studies help explain why human-to-human transmission of...

"Two new studies help explain why human-to-human transmission of the bird flu virus has so far not happened -- and might not happen in the future.

Both reports found the H5N1 virus prefers to settle in cells deep within the lungs, rather than in the upper respiratory tract, as happens with human flu strains.

That's important because "most of the coughing and sneezing that transmits flu is going to be from the upper respiratory tract, and not way down in the lower respiratory tract," explained Dr. Arnold S. Monto, a professor of epidemiology at the University of Michigan School of Public Health. "So, unless you have relatively close contact, you're not going to have much [bird flu] virus get out."

Full article at http://www.forbes.com/lifestyle/health/feeds/hscout/2006/03/22/hscout531699.html