How long does one remain infectious after a viral disease?
It depends on the virus causing the infection. In most cases, you are infectious even before you start feeling unwell or notice a rash. Common colds are infectious 1-2 days before the symptoms appear. You are most infective in the first 2-3 days when the symptoms are at their worst and you remain infectious till the symptoms have cleared. You can prevent the infection from spreading by following basic hygiene like using a handkerchief or a tissue when sneezing or coughing and by washing your hands often.