Temp basal in sickness

Jess has come down with a mild temperature and her readings have gone up quite high. She was 16 earlier and with boluses she's come down to 14, 13 and now 12. I've tested for Ketones and they're currently 0. She woke up this morning with a reading of 9 (high for her since being on the pump) and I've not managed to get them any lower all day. I think a temp basal is needed, is there any rule of thumb I should work to? What do others set their temp basal to during sickness?

Thanks, I've upped it by 20% over the next 4 hours and will take it from there. Am testing regularly to make sure the readings don't go any higher and will keep testing ketones every 4 hours or so until readings come back to below 9 or 10. Just when things were going so well, it's a shock to see such high numbers display on the test meter. Nearly half Jess' class were off school sick last week so there's definitely some sort of bug circulating, looks like it might be her turn to get it.

Just thought I'd update incase this of use to someone else in the future. The 20% increase in basal for 4 hours worked well. Within a couple of hours Jess' readings were back into the 6s. After the 4 hours (when the temp bolus had ended) they did climb again and I did some boluses to bring the readings down (I didn't get much sleep last night!). By this morning readings have returned to normal and been good all day so far, but she does have a nasty head cold and cough now, but temperature has come back to normal.