When is a cold or the flu contagious?
A person who has the common cold can be contagious - that is, they can spread the infection to others - for as long as three weeks. However, if you catch a cold, you are most contagious two to four days after your symptoms appear.
If you develop the flu, or influenza, you may be contagious one day before you begin to feel sick. After that, you remain contagious for up to one week. Children with the flu may remain contagious somewhat longer.
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