How and who does SARS kill?

Main Category: Flu / Cold / SARS
Article Date: 22 Apr 2004 - 0:00 PDT


Who does SARS kill?

No two cases of SARS are exactly the same. Depending on the age and fitness of the patient, the disease can run wildly different courses. Even the symptoms of fever and dry cough, initially included in the case definition for SARS, are no longer considered to be universal.

One pivotal point seems to occur at about the beginning of the third week after infection, when some patients, especially the young, improve.

Others, however, progress to a more severe form of the disease - their lungs become clogged with debris and fluid, which show up as dark lesions in chest X-rays. In about a fifth of all patients, this requires aggressive treatment such as mechanical ventilation. Even then, many of these people die.

Worldwide, the death rate from SARS seems to be about 10%. But individual risk factors vary considerably. For people over 65 years of age, more than half of those infected will die. Just about any lung ailment complicates the disease, and conditions such as emphysema are more common in the elderly.

Other concurrent infections may also be involved. Although it is now well established that the SARS virus can kill on its own, other viruses that have been isolated from patients with SARS could exacerbate the illness.

The ultimate cause of death also remains unclear. Does the virus kill directly by destroying cells in the lung, or does the immune system deliver a coup de grâce by fighting back too hard? By the time that most of the lung damage occurs, the amount of virus circulating in the blood has already peaked, suggesting the latter.

And the pattern of damage is consistent with an overload of cytokines - biochemical messengers that rev up our immune responses. But for the time being, pathologists are recording an open verdict.

• Additional
• References
• Citations