SARS

Severe Acute Respiratory Syndrome or SARS is a contagious viral disease that was pandemic from late 2002 to early 2003. It infected about 8,000 people during that time and caused about 700 deaths. It has influenza-like symptoms and the outcome of the disease is similar to influenza, although it has a somewhat higher mortality rate. However, SARS is caused by a type of virus different from influenza; much closer to that of the bird flu. Moreover, it is harder to develop SARS even if you are exposed to it.
As there's no vaccine for the disease, and no treatment, the best strategy is to contain cases when they appear. A medical history is vital when distinguishing SARS from influenza, as the only way to establish a definitive diagnosis is to tie the patient to a person who has already developed the disease. Once a SARS patient is identified, they must be kept in a negative pressure room (that, unlike a clean room, will not let air in the room out of the room) and staff dealing with the patient must follow strict antiseptic protocols. The virus is very hardy and can easily be passed from medical personnel to other patients.
In Toronto, one of the SARS outbreaks was traced to the use of part-time nurses who travelled from their job at one hospital to infect patients at their other job.
SARS' mortality rate ranges widely with the age of the patient. A patient under the age of 24 (including children) have only a 1% mortality rate. However, the mortality rate for patients over the age of 65 is close to 50%.
Severe acute respiratory syndrome at Wikipedia