Address of meeting with Section 31:
1044 North Maple
San Francisco
California
USA, Earth
94-1104-314159

Interestingly, the first five digits, 94110, make up a real San Francisco Zip Code. The final set of digits is simply the first six digits in pi. (3.14159)

Antaak says the virus is the worst threat to the Klingon Empire since the Hurq invasion. This is a reference to the DS9 episode "The Sword of Kahless", in which we learn the Hurq were a galactic power that conquered the Klingon homeworld about 1,000 years ago, plundering its treasures, including the sacred sword. The Klingons, true to their warrior nature, rebelled and cast away the Hurq, which is the Klingon word for "outsider." The Klingons probably stole the Hurq's technology, thereby acquiring warp drive and becoming a spacefaring empire (their lack of scientific initiative might explain why Klingon technology doesn't advance much in the 200 years between ENT and TNG, and likely hasn't changed much in the previous 500 to 1000 years, either).

In DS9's "Trials and Tribble-ations", when trying to figure out why the Klingons of the TOS era have smooth heads, O'Brien suggests genetic engineering and Bashir assumes a viral mutation. As we learn in this episode, both are correct.