Only certain infections, primarily involving bacteria with spirochetes, produce the relevant toxins as they die, so those should be the ones creating herx reactions.I have a suspicion, which I cannot prove, that most "Herxheimer" reactions are NOT Herxheimer reactions. Again, we infer the cause from the symptoms, but there are other causes. I suspect that some antibiotics for example can act as mitochondrial poisons.
However I suspect it is more likely to experience a real Herx reaction from oral antibiotics rather than IV antibiotics.
I'm certainly having some reaction, starting 5 days after beginning IV antibiotics for Lyme. I felt great the first 4 days, probably due to the IV fluids, and with no side-effects, which would seem to suggest that I'm not reacting directly to the antibiotics. It's an odd combination of feeling better in some ways and worse in others - like a healthy person with a nasty flu, instead of an ME patient.