DO NOT start where you left off (but before...). Your body needs time to regain strength and fitness after a serious (2 week) flu-like illness. Ease back into training regiment and allow your body and HR to determine when it's time to increase intensity, volume, etc. Unfortunately, you may have to adjust your race performance goals -- better that than suffering a more lengthy set back.

Thanks, Brushman! I did a 60 min. trainer ride this afternoon and my avg. and max bpm are still 10 bpm higher than expected. So I'm still recovering in some way. I'll take your advice and start the training volume/intensity at (at least) two weeks prior to illness. I don't know where I read you just start back up where you left off... obviously wrong!

My performance goal: surviving my first tri. I figured following my plan as close as possible would assure that and give me confidence. Just freaking out that I'm not able to do that now! Just wanna finish.

Thanks again. I'll calm down. :)

Good call.

Again, allow your mind, body, HR and recovery to determine your progress.

For me, after bouts of cold/flu, it usually takes about 7-10 days for HR to come back down and for body to again accept/recover efficiently from training loads undertaken prior to layoff.

We've all had to deal the inconvenient onset of illness during training cycles. Don't worry too much, however, once fully recovered, you'll quickly resume training as before. Just be sure to monitor your training stress levels and ensure adequate recovery sessions between hard workouts (maintain good hydration, etc...).

Any time I've had to suspend training either at one or all disciplines for an extended period (10 days+) I do the first run or ride afterwards on feel to see where I am. Don't be a slave to a plan that wasn't designed for your circumstances.
I've occasionally stopped running and/or cycling for a few weeks due to travel, injury or work commitments. I always back right off with the first run back, and I think it's asking for an injury to just jump back in full tilt. The bike is more forgiving but if I'd been ill I'd still go on feel for the first one and if perceived effort, HR and power (if used) don't line up as you'd expect, don't force it. Make it an easy session. Your priority should be getting up and going again, and feeling good. NOT hitting training plan targets. Once you've done a few sessions and feel you're back up to speed, maybe within a few days, then resume a little behind where you had stopped.

Remember, it's better to be 10% undertrained than 1% over-trained.
If you just want to finish, trust the groundwork you'd already laid before illness and let your body recover and get back into it. Push it a little, but not too hard. The biggest risk is that you panic, overdo it and either run yourself into the ground or develop an injury and have to take another break. You lost some time, it happens, you can't fix that, you can only work around it. See how it goes and re-assess your expectations if you have to, but you may not need to.

You need to be easing your way back into it, not doing 50 minute workouts with extended time in Z5. If you're really working that hard then you're overdoing it. If you're not working that hard and your HR is shooting sky high anyway then it's a sign that your body is still recovering and you're not ready for that kind of workout. Your best chance of doing your tri in a month's time is turning up healthy. Getting fit is always a secondary priority to getting healthy.

For N=1, after a long injury or illness when I'm not sure if I'm ready to resume normal training I tend to work my way back into things with a couple of short (max 30 minute run, maybe 45 minutes on the bike) sessions in zone 2-3. See how they go, see what after effects I have, then ramp up from there if all seems OK. Much better to err on the side of caution and take a couple of days extra to recover, than starting a couple of days too early and making yourself sick or injured again.