Hola Holly,

I can't find any question that relates the verb "ser" to being sick, but I've seen a question about professions that mentions nurses, though. Could it be possible that you've confused "enfermo" (sick) with "enfermera" (nurse)? Remember that when talking about professions, we always need the verb "ser" and not "estar".

Un saludo

Silvia

Hola Holly

These Kwiziq lessons will help you see in context both verbs ser and estar in these two situations: 

Using ser to say what you do for a living

Using estar to express a physical condition

Saludos

Inma