Sudden headache, then chills and feeling cold followed by a fever of 102. i did not have any other symptoms, this lasted one day. what could it be?

?viral infection: Sounds like a brief viral infection, maybe even mild flu. Seems you are done well. Do not worry, doesn't seem to represent threat in near future.

24 hr virus?: Most fevers are accompanied by headache.There are thousands of viruses. Most 24 hr viruses usually have fever as well a vomiting and diarrhea. Influenza is serious virus usually causes more severe and extended symptoms.Whatever it was it sounds self limited. If recurs should seek input by your physician, .