"If you wanted to kill as many people as possible, deniably and with no criminal consequences, what would you do? You’d do well to start with a bird flu. Bird flus are responsible for all the known flu pandemics: the great influenza that started more than a century ago, “Asian flu”, “Hong Kong flu” and “Russian flu”, which killed tens of millions between them. They also cause many of the annual outbreaks that slaughter hundreds of thousands of people.
Once you have found a suitable variant, two further components are required to weaponise it. The first is an amplifier. The best amplifier is a giant shed or factory in which thousands of birds are packed. These birds should be genetically homogenous, so that your viral strain can travel freely between them. Intensive poultry farms would serve very well. Before long, a low-pathogenic strain should mutate in these circumstances into a highly pathogenic variety.
To ensure maximum transmission, you should move some of the birds around, faster than the flu’s incubation period. You might carry them across borders. Some would be shifted to free-range or hobby farms, to enhance the possibility of infecting wild birds."