Distinguishing early pneumonia from a common flu or bronchitis hinges on monitoring the severity, duration, and specific nature of key symptoms. While flu symptoms (fever, body aches, fatigue) are often body-wide and intense but improve within a few days, pneumonia is characterized by a deeper, persistent cough that may produce green or rusty phlegm, and a high fever that spikes and lingers. The most critical red flag is difficulty breathing or sharp, stabbing chest pain that worsens with coughing or deep breaths—symptoms not typical of routine bronchitis or flu. Bronchitis typically causes a prominent, nagging cough but rarely brings a high fever or the profound fatigue and shortness of breath seen in pneumonia. If cold-like symptoms worsen after 3-4 days instead of improving, or if breathing becomes labored, it is essential to seek medical consultation promptly.