how long are chest viruses contagious
First, scientists involved with common cold research do not know exactly how long a person with a cold is contagious. Based on previous studies, their best guess is that a person becomes contagious about two to three days before developing the usual symptoms of a cold.irst, scientists involved with common cold research do not know exactly how long a person with a cold is contagious. Based on previous studies, their best guess is that a person becomes contagious about two to three days before developing the usual symptoms of a cold.