Brought my baby to HK (via CX) when she was 7 months as well! Agree with Mei that it's really more an issue of logistics planning than health risk. If you want to be sure, ask your PD for a go signal based on your baby's history of health. I actually asked mine if there were any additional vaccines we had to take since we'll be in an enclosed space with people (and their viruses) from all over the world. But she said no need. HKG is a very family-friendly airport. On our way home, baby was asleep in the stroller and we didn't have to take her out from check-in all the way to boarding, using "family lanes"! They even had a female security personnel check our stroller because my baby is a girl.
It's perfectly safe to bring an infant on a plane. I read somewhere that the infant involved in that case was already ill prior to boarding the plane. My LO was 7-weeks old when she made her first plane trip from HK back to SG. You'll want to worry more about the logistics of flying with a baby than anything else. Ask for a bassinet if possible. Even if your baby doesn't want to lie in it, it makes for a great storage area. And have milk ready. Once the plane doors close, babies will howl because of the depressurization so something to suck on helps. If you're flying CX or SQ, the flight attendants are usually great with passengers flying with infants.
Haha my baby flown on a plane when she is just 2 months. she will be fine. Anyway baby reacts to you and your husband reaction . if you are relax, baby will enjoy too :) enjoy your trip don't be so tense..