Well, pus indicates an infection, and if serious there should be a fever. If the condition is strep throat (tonsillitis), that is a specific type of infection caused by the streptococcus bacteria. Strep tonsillitis can cause secondary damage to the heart valves (rheumatic fever) and kidneys (glomerulonephritis). It can also lead to a skin rash (scarlet fever), sinusitis, pneumonia, and ear infections