How did dengue and 8 days of rest affect my body?

This is what dengue plus 8 days of no running did to my running fitness. I keep a very comprehensive running logs and from time to time, I will analyze my performance to see how much I've improved/regressed. So this is what happened.

I have been absent from the running scene for the past 2 weeks due to dengue fever. The last run I did was the Par series 2. I was still OK during the race in the morning and I'd actually planned to run a LSD later that day. However, my body started to feel quite unwell. At first, I thought I'd pushed too hard during the race which led to the soreness in my body but later that night, I got a very high fever. No surprise, a few days later, I was diagnosed with dengue and got admitted to the hospital.

I was actually in the middle of preparation for the SCKLM. Par series 2 was actually already at week 14 and everything was going on pretty smoothly until dengue hit. Based on my past experience, 8 days of no running won't actually cause a drastic decline but instead, this dengue put me 10 weeks behind from where my fitness was.

How do I know it's 10 weeks behind? I've got a very simple way to judge my fitness level. This is how I keep track: Based on the HR value at a certain pace, I can figure out how hard I'm running and from there, I can compare the HRs and find out my fitness level. So from time to time, I will check my HR and find out my 10k predicted race time so I know how fast I can run.

So this is how my fitness level looks like over the 16 weeks of training.

Performance Improvement Line Graph

Date     HR  Pace 10kTime Note
21/03/16 156 6:02 0:52:30 1st training after 3 months of hibernation
22/03/16 149 5:51 0:48:20 1st week
25/03/16 161 5:27 0:49:15 1st week
29/03/16 151 5:35 0:47:00 2nd week
01/04/16 152 5:35 0:47:15 2nd week
22/04/16 143 5:42 0:44:50 5th week, after Nike
27/04/16 143 5:26 0:42:45 6th week, after BDB
02/05/16 140 5:42 0:43:50 7th week
12/05/16 154 4:54 0:42:10 8th week
13/05/16 138 5:44 0:43:15 8th week
15/05/16 141 5:35 0:43:15 8th week
21/05/16 151 5:07 0:43:00 9th week
26/05/16 147 5:05 0:41:30 10th week
29/05/16 22k Race Time: 1:39:09, 10k equivalent 0:42:20
08/06/16 146 4:59 0:40:10 12th week
15/06/16 145 4:59 0:40:00 13th week, after Par series 1
18/06/16 146 4:56 0:39:45 13th week
22/06/16 143 4:53 0:38:25 14th week
24/06/16 147 4:56 0:40:10 14th week, 2 days before Par series 2
10/07/16 160 4:56 0:44:10 16th week, 4th training after dengue
13/07/16 154 4:53 0:42:00 17th week

I measured my HR during my 4th training post-dengue and it reached 160 at 4:56 pace, which I could easily achieve 2 weeks before with just 147 HR. 13 beats higher in HR to me is equaled to about 4 minutes slower in 10km race time. It was just hard at the beginning. I still remember I could only sustain this pace for about 5km. Good news is that looking at my 2nd measurement 3 days later, I think I can regain my fitness pretty quickly this time around. Anyway, this has affected my SCKLM training quite badly. It's only less than 4 weeks now, and I will have to revise my goal. I will still aim for it but with a slightly slower finishing time. Let's see how it goes.