Don’t worry about bacterial meningitis if there’s no fever.
For the febrile “headache” patient [who probably has the flu], worry if the patient looks real sick, or can’t bend their neck. For subacute meningitis (e.g. TB), or CNS abscesses, be alert if there’s only fever and “headache,” without myalgias (and certainly without cough).
Encephalitis (often afebrile) presents with more confusion than headache.
See posting Acute Headache -3.