A university professor and two students recreated a virus identical to the one that caused the devastating 1918 Spanish Flu pandemic. If they can do it, so can terrorists.
Spanish Flu Killed 50 Million. Terrorists Can Now Create Synthetic Version of the Virus.
Making a virus identical to one which existed in the past isn't particularly worrying, because the original virus is already in the wild (except for the very few which are extinct, because of vaccination efforts).
The real trick is creating a novel virus, which our immune systems aren't all accustomed to already, and that's a whole different challenge. I don't think our genetic engineering technology is at a point where that's a realistic concern yet
Viruses mutate over time. So the 1918 flu has not been circulating for over 100 years. No one under 107 has been exposed to the virus that wiped out millions aka it's novel.
White Plague by Frank Herbert.
What's the claim about terrorists about?