Medical triage is the sorting of incoming patients into three categories (thus tri-):

• those who are likely to die despite intervention
• those who are unlikely to die quickly and whose condition may stabilize without intervention
• those who will die without immediate intervention but who will likely stabilize with intervention now

The last category gets all the attention until a crisis eases and there is sufficient equipment, doctor, nurse and orderly time to tend to the others. By that time most of the patients in the first category will have died without attention.

The need for triage is caused directly by a lack of surge capacity in a health care system: if there are sufficient attendants to deal with all incoming patients, then, there is no need for triage. In many one-time cases of large-scale trauma? such as natural disaster?s or accident?s or attacks, this capacity isn't available. In extended circumstances that also have the capacity to disable health care worker?s, such as pandemic influenza, there will definitely be a need for triage. Another non-triage aspect of this problem is that patients who have low potential for recovering a high quality of life may lose attention or equipment, e.g. there are only 140,000 ventilators in American hospitals, a tiny fraction of what would be required to deal with millions of flu patients.