Viral Contagiousness
According to modern medical research, viral and infective illnesses like ear infections in infants have a lifetime of contagiousness.
The general rule of thumb is that the child is no longer contagious after 24 hours has past since the last fever, or after 4 doses of the antibiotic has been administered.
The child is still mildly contagious, but would not be spreading terminal amount of the contagion.