Hi, Persistent cough and severe lethargy can be symptoms of several different health conditions, so it is difficult to provide a definitive answer without a proper medical examination. However, based on the information provided, there are a few possibilities that could explain these symptoms: * Post-viral cough: It is common for the cough to persist for several weeks after a viral infection has cleared up. This is known as post-viral cough, and it can be accompanied by fatigue and general malaise. There is no specific treatment for post-viral cough, but over-the-counter cough suppressants and staying hydrated can help alleviate the symptoms. * Pneumonia: Sometimes, a bacterial infection can develop after a viral infection has weakened the immune system. Pneumonia is an infection in the lungs that can cause a persistent cough, fatigue, and difficulty breathing. Treatment for pneumonia usually involves antibiotics and rest. * Asthma: In some cases, a persistent cough could be a symptom of asthma. Asthma is a chronic condition that affects the airways, and it can cause coughing, wheezing, and shortness of breath. Asthma treatment usually involves inhalers and other medications to manage symptoms. * Allergies: If the cough is accompanied by sneezing, a runny nose, and itchy eyes, it could be a sign of allergies. Allergies can cause a persistent cough, and treatment typically involves avoiding the allergen (if possible) and taking antihistamines. Your friend needs to see a healthcare provider for a proper diagnosis and treatment plan. The healthcare provider may recommend further tests, such as a chest X-ray or blood tests, to determine the cause of the symptoms. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician