Further research needed to establish likelihood of transmissibility of disease by public access to the countryside.

BBC: At a glance: NFU disease report

If H5N1 ever acquired this kind of transmissibility, he says, it probably could not be stopped without a vaccine.

FORBES: Magazine Article

But here, too, transmissibility can be reduced dramatically.

ECONOMIST: A turning-point for AIDS?

In a report published late Thursday in the New England Journal of Medicine, samples from three patients -- all of whom died -- had mutations that have previously been shown to increase transmissibility, and to help the virus grow in a mammal's respiratory tract.

CNN: New bird flu well-adapted to infect people