@fify-- Leaving strep throat untreated be deadly for children and probably for adults too. I remember reading in the news about a child who died from complications of strep throat. He didn't get treatment in time and developed kidney damage from the infection. Children are more sensitive and fragile than adults and infections are extra dangerous for them.
Also, the fever that strep throat causes can lead to brain damage in very young children. If it doesn't cause death, it can cause mental illness or retardation. Strep throat should not be taken lightly.