Chickenpox is contagious before any rash appears, which is why it spreads so easily among kids. Here's how the virus moves and when exposure actually happens.
A dry cough can stem from many causes, including post-nasal drip, acid reflux, or even your blood pressure medication. Learn what's likely behind yours and when to see a doctor.
Robert Koch helped establish that specific germs cause specific diseases, developed key lab techniques, and won a Nobel Prize for his work on tuberculosis.