In general, viral infections are milder than bacterial infections, but they tend to last longer. You will feel very sick for 1 to 3 days and then you will start to feel better, but some of your symptoms may linger. Symptoms that linger for a week or more may be a virus.  It's important to stay vigilant and talk to your doctor about antibiotics if symptoms last for a while. Viruses can morph into things like sinus infections or increase the risk of middle ear infections, which may result in you developing a bacterial infection as well. When you blow your nose or cough up mucus, pay attention to the color. While it may feel a little gross, color can be an indicator of whether you have a viral or bacterial infection.  Thin and clear mucus is more likely to be a viral infection. Dark, greenish mucus is more likely to be a bacterial infection. However, mucus color is not a 100% accurate indicator of whether you have a viral or bacterial infection. Make sure to weigh in other factors. A sore throat is common for both viral and bacterial infections. Checking for a sore throat is the most common test that will be performed in your doctor’s office to determine if you need antibiotics right away. Certain types of sore throats can indicate a bacterial infection. For example, white spots are generally caused by bacteria. A sore throat without other symptoms, such as a runny nose or sneezing, may be a bacterial infection such as strep throat. Fevers can be present in both viral and bacterial infections. However, fevers differ slightly with different types of infections. In bacterial infections, fevers tend to be higher. With a bacterial infection, fevers get worse after a few days while they tend to improve a few days in with a viral infection. The normal human body temperature runs between 97.8° F (36.5°C) and 99°F (37.2°C).

Summary:
Track the length of your illness. Pay attention to the color of your mucus. Observe your throat. Evaluate your fever.