Headache caused by and occurring in association with other symptoms and/or clinical signs of a systemic viral infection, in the absence of meningitis or encephalitis.
A. Headache of any duration fulfilling criterion C
B. Both of the following:
1. systemic viral infection has been diagnosed
2. there is no evidence of meningitic or encephalitic involvement
C. Evidence of causation demonstrated by at least two of the following:
1. headache has developed in temporal relation to onset of the systemic viral infection
2. headache has significantly worsened in parallel with worsening of the systemic viral infection
3. headache has significantly improved or resolved in parallel with improvement in or resolution of the systemic viral infection
4. headache has either or both of the following characteristics:
a) diffuse pain
b) moderate or severe intensity
D. Not better accounted for by another ICHD-3 diagnosis.