How long are people contagious when they are infected?
The answer depends on the study you read. A recent study by German scientists suggests that people who test positive are most contagious before they've started exhibiting symptoms and during the first week that symptoms show up. Symptoms can appear anywhere between two and 14 days after infection. On the plus side, the same study shows that after about eight to 10 days of symptoms, patients were no longer infectious. This seems to show that though the disease is pretty contagious at the onset, the body gets rid of the virus quickly once antibody production turns on (which is typically within six to 12 days).
Yet another study, however, suggests the virus can endure in the body for a median of 20 days after infection, and as long as 37 days in some cases.
The rule of thumb being promoted so far is to remain quarantined for 14 days from the moment you develop symptoms.