Fevers are caused in most cases by viral or bacterial infections, such as otitis media (ear infection), upper respiratory infection, pharyngitis (throat infection), pneumonia, chickenpox, and urinary tract infection.
Environmental and other conditions, such as breathing secondhand smoke, breathing polluted air or chemical fumes, or swallowing substances that burn or scratch the throat can also cause pharyngitis.
In about 40 percent of these cases of pharyngitis, it is never clear what caused the sore throat.
About 10 percent of children who go to the doctor each year have pharyngitis.
"Pharyngitis." American Family Physician 69, no. 6 (March 15, 2004): 1465.