Learning lessons from the SARS pandemic

April 2003

It would appear that influenza is not the only respiratory infection that arises in China and seems capable of rapidly spreading around the world. The status of severe acute respiratory syndrome (SARS) is a rapidly evolving story, and it is difficult to know how to assess the situation at the present time. It is becoming clear, however, that the public panic level is already rising; though not yet at the level of hysteria, it could approach that in the days and weeks ahead, depending a great deal on how this apparent pandemic unfolds. The recent SARS death in Bangkok of Dr. Carlo Urbani, the Italian epidemiologist who first identified the spreading SARS pandemic, has only contributed to the level of public concern.

WHO became aware of rumors of an atypical respiratory infection with pneumonia occurring in the Guangdong Province in China in early November and December 2002. The Chinese government, however, was not particularly forthcoming at that time with clinical or epidemiological details. Only after SARS spread within mainland China, and then to Hong Kong, Singapore, Vietnam and Thailand did it become apparent to WHO epidemiologists that a new respiratory infection was emerging. Indeed, it was less than a month ago that WHO issued its first Global Health Alert, calling the attention of the public health community — as well as the public at large — to this problem.

As of presstime, the global status of SARS is as follows: there are now more than 2,600 suspect cases worldwide, including more than 90 deaths. Although most of the cases are in Asia (especially China, Hong Kong, Singapore and Vietnam), there are also small numbers in Europe. In the Western Hemisphere, there is a cluster of cases in the Toronto area, and in the United States, there are 62 suspect cases with (so far) no deaths. The case counts include not only those who are suspected of a “primary” infection acquired while traveling in an endemic area, but also, in some instances, close family contacts and health care workers who are suspected of being infected while caring for patients with suspect SARS.

Which virus?

Suspicions about etiologies have been many, including influenza initially, then other agents such as metapneumovirus, then a paramyxovirus and now, most recently, a coronavirus. Coronaviruses have previously been associated primarily with a mild upper respiratory syndrome and are estimated to cause around 15% of common colds. Influenza was everyone’s first choice, and certainly for some of my contemporaries and me, the situation is very reminiscent of the early days of the Asian influenza pandemic in 1957. Enough good laboratories have looked for evidence of influenza virus infection in SARS patients, however, and have failed to find it. That possibility must now be discarded. Since the putative coronavirus etiology has been stable for almost a week now, one assumes there is growing evidence to support that etiology, although the strength of that evidence is not yet clear.

The case definition currently in use by CDC, and I believe by WHO as well, is woefully but necessarily quite nonspecific. The key marker is still travel within the previous 10 days in a SARS area, which presently includes mainland China and the Hong Kong Special Administrative Region, Hanoi and Singapore; or a close contact of a suspect SARS case, plus a measured temperature of >38°C and one or more clinical findings of respiratory illness, such as cough, dyspnea, difficulty breathing or radiographic findings of pneumonitis or adult respiratory distress syndrome. As nonspecific as that definition is, however, it is still quite stringent, for good epidemiological purposes, tilting toward the “severe” end of the infection spectrum. Thus, the definition may be excluding for now an unknown number of less severe infections that are completely escaping detection. Resolution of that question must await clear definition of the etiologic agent, plus a serologic screening test to identify those recently infected.

Mostly adults affected

Most suspect cases so far have been adults, age 25 to 70, most of whom have been previously healthy; relatively few cases have been reported in children <15 years. In part, this simply represents the consequence of the case definition being used. A two-phased illness is described in the Morbidity and Mortality Weekly Report preliminary clinical description: The first begins after a two- to seven-day incubation period, and consists of fever, sometimes high and accompanied by rigors, and mild respiratory and constitutional symptoms. The second phase begins after three to seven days and includes respiratory distress, hypoxemia and in 10% to 20% of patients is severe enough to require intubation and ventilatory support. Yet, the calculated mortality rate is still only 3.6% (58/1622), although some of the reported cases may yet die as their illness progresses.

CDC recommendations

Readers with hospital infection control responsibilities should be aware of the current CDC recommendations for infection control precautions and exposure management. They are necessarily quite conservative, and reflect the many uncertainties regarding SARS transmission. Thus, both contact and airborne precautions are recommended, in addition to standard precautions. Further recommendations deal with adaptation of these to management of close contacts in the home setting.

Easily the best source of current data is the CDC SARS Web site, at www.cdc.gov/ncidod/sars. It is regularly updated and has links to WHO, other international health jurisdictions and state health departments as well.

We are already being treated to photographs of people going about the streets of Hong Kong and other cities in the endemic areas wearing masks — very reminiscent of public behavior during the 1917-18 influenza pandemic. It is doubtful that such masks prevented anything then (perhaps they made the wearer feel more secure) and equally doubtful they will prevent anything today. In my part of the world, one need only travel 30 miles up the road to Boulder, Colo. (lovingly referred to locally as the People’s Republic of Boulder), to see the same thing. A nurse who spent about 10 days in China is believed to be a suspect case, and is presently quite ill in the Boulder Community Hospital; the information has unfortunately become public knowledge. (Perhaps, some good will come from HIPAA [Health Insurance Portability and Accountability Act of 1996] after all!)

There is one very bright silver lining to all this, and that is that we have this information at all. Thirty to 40 years ago this wealth of information could not have happened! Only five months have elapsed since cases first started to occur in China unbeknownst to us, and only several weeks have elapsed since WHO first sounded its global health alert. The amount of information being put together and made available by global public health authorities under WHO auspices has truly been astonishing. The threat of an emerging infectious disease has been of great concern for the last decade; in the case of SARS, the organization and speed of the global public health response is both gratifying and reassuring.