Is it flu or SARS? MDs gear up for a difficult winter
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* Allison Gandey

Differentiating between SARS and influenza is a tricky business, and as Canada heads into its winter months health officials are concerned about the possibility of widespread false alarms. This means that important decisions will have to be made about how to handle patients with flu-like symptoms.

![Figure1](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/169/8/821.1/F1.medium.gif)

[Figure1](http://www.cmaj.ca/content/169/8/821.1/F1)

Figure. **Who should be isolated?** Photo by: Canapress

“We have a great number of problematic questions to answer,” says Dr. Frank Plummer, scientific director of Health Canada's National Microbiology Laboratory in Winnipeg. “When do we test for SARS? And when do we isolate people?”

The World Health Organization (WHO) says this problem requires immediate preventive measures. “Because this disease starts the same as influenza and transmits to health care workers, people will have to be isolated,” says Dr. David Heymann, the executive director of communicable diseases. “I'm sure you can see the implications.”

He says the potential confusion surrounding the SARS/flu diagnosis is the reason WHO is recommending that elderly and immunocompromised people or those who have underlying chronic cardiopulmonary, renal or metabolic disease be vaccinated against influenza this fall. Influenza typically infects 10% to 20% of the population during seasonal epidemics. Each year, 3 to 5 million cases of severe flu-related illness occur worldwide, and at least 250 000 to 500 000 people die.

Klaus Stöhr, head of WHO's influenza program, says physicians must remain alert. “The earlier we intervene, the less likely the disease will spread.”

Several respiratory illnesses occur less frequently when temperature and humidity are high, and the number of cases increases with the return of cooler weather. There is some speculation that SARS might follow this seasonal pattern.

WHO's case definition for SARS (September 2003) includes these signs:

· fever ≥ 38°C AND

· one or more symptoms of lower respiratory tract illness (cough, difficulty breathing, shortness of breath) AND

· radiographic evidence of lung infiltrates consistent with pneumonia or respiratory distress syndrome (RDS) OR autopsy findings consistent with the pathology of pneumonia or RDS without an identifiable cause AND

· there is no alternative diagnosis.

Under a microscope, the novel coronavirus believed to cause SARS (SCoV) appears as an irregular sphere, engulfed by peplomers that look like a crown (*corona*).

SARS was first recognized in China's Guangdong Province in November 2002. It spread to Hong Kong in February, and eventually to more than 30 other countries. More than 8400 people worldwide contracted SARS and over 900 of them died, including 43 in Canada. Currently, there is no reliable point-of-care diagnostic test for SARS, no effective treatment and no vaccine.

Dr. David Patrick, director of epidemiology at the British Columbia Centre for Disease Control, is concerned about SARS diagnostics. Although testing for infection with the SARS virus proved effective during this year's outbreak, Patrick questions the overall efficacy of these tests and notes that false- positive results cannot be tolerated.

Plummer says physicians must understand that not everyone who presents with a coronavirus develops SARS, and that most people who have SARS do not transmit it to large numbers of people because infection appears to require close and sustained contact.

Patrick says it is time to return to the old standbys to combat SARS: wash hands frequently, stay home when sick and avoid hand shakes and other similar physical contacts during flu season. “You've heard of the ‘new normal’?” Patrick asks. “Well, that's a bit of a misnomer. It's actually the old normal.” — *Allison Gandey*, CMAJ