The use of articles for symptoms is something which confuses a lot of non-native speakers of English.
How can a cough be countable?
Are you counting the number of times the patient coughs in front of you?
It’s not that the symptom at the time the patient is experiencing it is countable, just that they can have the same symptom many times throughout their life. Most symptoms therefore require an article.
Here are some common examples:
Read more about articles for medical procedures.
Read more about articles for medical conditions.
Read more about articles for job roles.