It could be a new dark wizard. There are always new threats emerging in the fanfiction world. This new dark wizard might have a vendetta against Harry and uses a special spell or potion to make him cough up blood.
Another possibility is internal injuries from a battle. Fanfiction often has intense battles that are not part of the original story. Harry could have been hit by a powerful spell during a fight that caused internal damage, which then makes him cough up blood.
It could be due to a dark curse or spell. Maybe he was attacked by a powerful dark wizard using a forbidden spell that affects his internal organs and causes bleeding.
Well, it could be a result of a dark spell cast on him by a Death Eater. Maybe they found a new and insidious way to harm him without leaving an obvious trace.
It could lead to a discovery of a hidden plot against Harry. His coughing up blood might be a sign that there is a much bigger conspiracy at play, perhaps involving someone close to him who wants to weaken him for some ulterior motives.
One interesting fanfiction could be 'The Darkening Plague' where Harry's coughing blood is a sign of a dark curse spreading in Hogwarts. It has a great plot that weaves mystery and magic.
The sudden coughing of bright red blood could be caused by a variety of reasons. These included bronchial diseases, lung diseases, cardiac diseases, general diseases, and drug factors. The specific cause of the disease needed to be confirmed through the relevant examinations and medical history collection in the hospital. The common causes of the disease included bronchiectasis, lung inflammation, lung cancer, and so on. Therefore, if there is a sudden cough of bright red blood, it is recommended to seek medical attention in time for relevant examination and treatment.
Coughing up blood was a symptom, usually referring to coughing up bright red blood. There were many reasons for hemoptysis, including bronchial disease, lung disease, cardiac disease, general system disease, and drug factors. The specific reason needed to be confirmed through the relevant examinations and medical history collection in the hospital. The common possible causes included bronchiectasis, lung cancer, lung edema, and so on. If hemoptysis occurs, it is recommended to seek medical attention in time to determine the specific cause and carry out targeted treatment.
He could be secretly worried. Snape might use his knowledge of potions and dark magic to try and find a cure or at least a way to stop the bleeding. He may also be conflicted, as his past relationship with Harry and his loyalty to different sides in the wizarding world play a role in how much he wants to help Harry.