Severe Acute Respiratory Syndrome (SARS)

We all recognize that our knowledge about SARS is changing daily, but here is a review as of late April 2003.

Introduction:

In the second week of March 2003, the World Heath Organization (WHO) received reports of greater than 150 cases of acute respiratory illness associated with pneumonia. The majority of these cases were from Southeast Asian countries of China (including Hong Kong), Vietnam, Indonesia, the Philippines and Singapore. China has reported more than 1300 cases of infection and 64 deaths, most in the southern province of Guangdong, where the first cases emerged in November 2002. The appearance of many cases over a short period of time in the absence of a clear cause of the pathogen along with the spread between countries and the concern of a potential pandemic has led the WHO to issue a global alert. The WHO has adopted a pivotal role in the investigation of the outbreak, with the development of a case definition for Severe Acute Respiratory Syndrome (SARS). Rapid dissemination of information on SARS has occurred via the Internet. This article provides a snapshot of the current knowledge on SARS with reference to the current peer reviewed literature and medical information on the Internet

Epidemiology:

The current (April 12, 2003) case total reported is 2,960 cases worldwide with 119 deaths.

At the present time, there are 1,309 cases and 58 deaths in China, Hong Kong has 1108 cases with 35 deaths, Canada presently reports 101 cases with 10 deaths, and the USA 166 cases with no deaths.

Preliminary information from Hong Kong has tracked the epidemic to a single visitor from main land China. As the epidemic has progressed, knowledge of the condition has improved. While the true danger of the epidemic is currently unknown, the condition, while passed from human to human, does not appear to be as transmissible as first feared. With most secondary cases being reported in close contact of the case, or health care workers involved in the care of a SARS patient.

Causative agent:

The illness appears to be viral in origin, with a coronavirus as the most likely culprit. SARS is not uniformly deadly nor does it seem to be particularly infectious once people with the virus are prevented from coughing or sneezing on others. The virus has been grown in monkey cells and the National Institute of Allergy and Immunology are commencing developing potential vaccines, although a vaccine built for clinical care may be some ways off.

Clinical presentation and course of illness:

The clinical illness, SARS, is characterized by a prodromal phase, typically with sudden onset of high fever accompanied by rigors, headache and myalgia, with, in a few cases, diarrhea. Mild respiratory symptoms may be present, but typically these develop over the next few days with a non-productive cough and dyspnea which may be accompanied by hypoxemia. In 80-90% of cases, improvement occurs after 6 or 7 days. In approximately 10%, progressive respiratory failure develops, which may require assisted ventilation. The case fatality rate to date is 2-5%. Many of the fatalities have been elderly people or patients suffering from other chronic health problems such as heart or kidney disease. But six deaths were reported in Hong Kong over the weekend with people ranging in age from 35 to 52 with no prior health problems.

Laboratory investigations:

Non-specific with leukopenia, thrombocytopenia, abnormal liver function tests and raised creatinine phosphokinase are reported.

Chest radiograph:

May be normal throughout the illness but typically shows patchy shadowing which may become confluent.

Therapy:

No treatment has been found to influence disease progression and management therefore should be directed towards, droplet precautions (mask on patient, respiratory isolation), along with supportive care including fluid balance and gas exchange. However, because of similarity to other pneumonias, appropriate broad-spectrum antimicrobial therapy, tailored to the common pathogens and local antibiotic resistance should be given until a precise diagnosis or specific causative agent is identified.

 

Andrew McIvor

Thanks to Dr. Scott Rappard, Consultant Respirologist at St. Martha's Regional Hospital, Antigonish, Nova Scotia for reviewing the draft copy of this article.

References:

  1. Update: Outbreak of severe acute respiratory syndrome - worldwide 2003. MMWR March 28, 2003/52(12); 241-248.
     
  2. Preliminary clinical description of severe acute respiratory syndrome. MMWR March 28, 2003/52(12); 255-256.
     
  3. A major outbreak of severe acute respiratory syndrome in Hong Kong. Lee N, Hi D, Wu A, et al. N Eng J Med. Mar 31,2003. www.nejm.org.
     
  4. Identification of severe acute respiratory syndrome in Canada. Poutanen SL, Low DE, Henry B, et al. N Eng J. Med. March 31, 2003 www.nejm.org.
     
  5. Faster... but fast enough? Responding the epidemic of severe acute respiratory Syndrome. Gerberding JL. (Editorial) N Eng J Med. Apr 2, 2003 www.nejm.org.
     
  6. Case clusters of the severe acute respiratory syndrome. Drasen JM. (Editorial) N Eng J. Med. . Mar 31,2003. www.nejm.org.
     
  7. Identification of a novel coronavius in patients with severe acute respiratory syndrome. Drosten C, Gunther S, Preiser W et al. N Eng J Med. Apr 10, 2003 www.nejm.org.
     
  8. A novel coronavirus associated with severe acute respiratory syndrome. Ksiazek TG, Erdman D, Goldsmith C et al. N Eng J Med. Apr 10, 2003. www.nejm.org.
     
  9. Coronavirus as a possible cause of severe acute respiratory syndrome. Peiris JSM, Lai ST, Poon LLM. Published on line Lancet, April 8, 2003.
     
  10. Novel coronavirus and severe acute respiratory syndrome. Falsey AR, Walsh EE. Published on line Lancet, April 8, 2003.
     
  11. Guideline on management of severe acute respiratory syndrome (SARS). Ho W. Published on line Lancet, April 8, 2003.

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