A quote from The Influenza Times, 4th ESWI Influenza Conference 11-14 September 2011, Malta:
A “stupid” experiment leads to a valuable result Fouchier and his team’s biggest discovery, however, was based on what he termed a “stupid” experiment. He and his team introduced mutations, under strict laboratory safety procedures, by reverse genetics into laboratory ferrets. They then collected a nasal wash from each infected ferret and inoculated another ferret after a few days. They repeated this process ten times. The result? H5N1 had been transmitted to three out of four ferrets. “This virus is airborne and as efficiently transmitted as the seasonal virus,” said Fouchier. His research team found that only 5 mutations, 3 by reverse genetics and 2 by repeated transmission, were enough to produce this result. “This is very bad news, indeed,” said Fouchier.
I've noticed several design suggestions in your code.