Your risk of getting malaria depends on your age, history
of exposure to malaria, and whether you are pregnant. Most adults who have
lived in areas where malaria is present have developed partial immunity to
malaria because of previous infections and so almost never develop severe
disease. But young children who live in these areas and travelers to these
areas are especially at risk for malaria because they have not developed this
Public health scientists verified that a common virus -- a coronavirus -- that has become more severe as the likely cause of severe acute respiratory syndrome (SARS). Many people wonder just how scientists know that the cause is a virus and, more importantly, this particular virus.
In 1890, Robert Koch described the basis rules that scientists use to determine if an infectious organism causes a specific disease. These four rules are called "Koch's postulates."
The organism must be found in...