A Wyoming University entomology professor told BBC radio yesterday that infectious diseases could be brought into a country and spread by using infected insects. According to him, it would be an inexpensive and easy method of biological warfare.
It's hard to know what to make of this, given that it's the theory of only one scientist. I'm not sure exactly how it would work. The article doesn't give details, which is probably a good thing. Jeffrey Lockwood, the scientist in question, has written a book about it, which would probably be interesting reading.
Assuming that his theory is plausible, this demonstrates yet again how difficult it is to play defense against terrorism. Terrorists who are not stopped before they actually strike always have the advantage of timing and strategy. They can pick their method. And it's likely that they'll choose something we aren't guarding against and just aren't prepared for. Resources are limited, and we can't defend adequately against everything.