Do Some Patients with SARS Have Mild Disease?

Summaries for Patients are a service provided by Annals to help patients better understand the complicated and often mystifying language of modern medicine.

Summaries for Patients are presented for informational purposes only. These summaries are not a substitute for advice from your own medical provider. If you have questions about this material, or need medical advice about your own health or situation, please contact your physician. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the American College of Physicians.

The summary below is from the full report entitled "The Spectrum of Severe Acute Respiratory Syndrome–Associated Coronavirus Infection." It is in the 20 April 2004 issue of Annals of Internal Medicine (volume 140, pages 614-619). The authors are T.H. Rainer, P.K.S. Chan, M. Ip, N. Lee, D.S. Hui, D. Smit, A. Wu, A.T. Ahuja, J.S. Tam, J.J.Y. Sung, and P. Cameron.

What is the problem and what is known about it so far?

Severe acute respiratory syndrome (SARS) is an infectious disease caused by a virus called coronavirus. SARS can spread quickly from person to person and cause large outbreaks. Symptoms, including fever, body aches and pains, cough, and trouble breathing, may progress rapidly. Patients with severe pneumonia-like symptoms sometimes need machines to help them breathe. About 10% may die. Much of the information related to symptoms caused by SARS comes from studies of patients who were hospitalized for pneumonia. We do not know whether some patients infected with the SARS coronavirus have only mild or no symptoms.

Why did the researchers do this particular study?

To see whether some people with SARS have mild or no symptoms.

Who was studied?

1221 people attending a SARS clinic at a university hospital in Hong Kong between 12 March and 12 May 2003.

How was the study done?

The researchers asked patients about symptoms, examined them when they first visited the clinic, followed up patients who had symptoms, and arranged frequent chest x-rays. The researchers also collected blood samples at the clinic visit and tried to obtain follow-up information and blood samples 3 weeks later. They tested the blood samples for cells dispatched by the immune system to fight SARS (SARS coronavirus antibody). The researchers considered patients to have confirmed SARS if antibodies were detected.

What did the researchers find?

Almost all of the patients diagnosed with SARS by using the blood test had severe symptoms with pneumonia and were hospitalized for treatment. Of 910 patients who were managed without hospitalization, only 6 had positive results on blood tests for SARS coronavirus antibody. Five of the 6 patients had normal chest x-rays. Four patients had symptoms such as body aches, chills, coughing, and feeling feverish.

What were the limitations of the study?

The researchers could not obtain follow-up blood samples from almost half of the patients because these patients declined further testing. The research involved only patients who visited a SARS clinic. Some people living in the community who were infected but had minor or no symptoms might not have visited the clinic.

What are the implications of the study?

Few people with SARS have mild or no symptoms.