There is a massive difference between "there are a few thousand people in the world who might have the specialized knowledge to kill billions" and "anyone with a handful of GPUs or access to a handful of cloud systems could have a conversation with LatestAIUnlimited-900T and make a few specialized mail orders".
The Venn diagram of "people who could arrange to kill most of humanity without being stopped" and "people who want to kill most of humanity" is thankfully the empty set. If the former set expands to millions of people, that may not remain true.
Generating bioweapons is not a trivial task even if you know exactly "how to do it". Ask any biologist how easy it is to grow X your very first attempt.
Then remember buying starter cultures for most bioweapons isn't exactly easy and something anyone is allowed to do.
Even an omniscient AI cannot overcome a skill issue
there's a much easier way to create a global pandemic: wait for the next Ebola outbreak, hop on a plane, get infected, fly to NYC and spread your bodily fluids everywhere. I was (pleasantly) surprised that ISIL didn't try this.
and making a pandemic virus is considerably more involved than making "a few specialized mail orders." and if it becomes easier in the future, far better to lock down the mail orders than the knowledge, no?
Thankfully, Ebola is not a good candidate for a global pandemic for a number of reasons. It is much easier to avoid a virus spread by bodily fluid contact than one which is airborne, and Ebola tends to kill its hosts rather quickly. I'm more excited about SARS-CoV-5 (Captain Trips).
The Venn diagram of "people who could arrange to kill most of humanity without being stopped" and "people who want to kill most of humanity" is thankfully the empty set. If the former set expands to millions of people, that may not remain true.