Pedestrians wearing surgical masks cross a street in Hong Kong, Tuesday, April 29, 2003, as a precaution against the SARS virus that has killed more than 130 people in the territory. (AP Photo/ Lo Sai Hung)

Ten years ago this spring, reports in virtually every media outlet in the world gave distressing news of an outbreak of a lethal and highly contagious illness that eventually became known as Severe Acute Respiratory Syndrome, or SARS.

The attention generated enormous reaction, some of it bordering on panic, forcing quarantines in some areas and leading to sharp declines in world travel and global commerce, at a cost measured later of more than $50 billion.

The outbreak also forced revolutionary changes in the world of public health and epidemiology — changes that a decade later have left us better prepared for the next threat posed by yet another new infectious agent, something experts say is inevitable.

Because of SARS, there is now a more vigilant worldwide network prepared to detect the possibility of a pandemic, and better able to issue the necessary warnings. Because of that, governments will be better positioned to take rational and strategic actions to contain an outbreak without spreading unnecessary alarm.

Ironically, this has come as a direct result of actions taken at the time that were seen then as incendiary and irresponsible. But now, in the sharper lens of hindsight, the controversial decision by the World Health Organization in March 2003 to issue a global health alert, appears more courageous than capricious.

At the time, there was criticism it led to an "overkill" response that fueled panic, caused unneeded restrictions on travel and other moves that simply over-estimated the actual threat. They say the ultimate toll of SARS — 8,273 confirmed cases and 775 deaths worldwide — demonstrate the illness was not as virulent as the WHO's actions caused many to believe.

But consensus among public health experts is the warning probably saved many thousands of lives. The WHO's own analysis shows that the alert issued in the form of a press release in which the illness was first named, included a demarcation of areas with severe outbreaks and those with lesser risk. Later analysis showed that in those high-risk areas, the rate of infection dropped significantly after the alert was issued, as people began taking more precautions against exposure.

In retrospect, the only lingering criticism of the global alert is that it came too late. The WHO said the government of China, where the outbreak originated, refused early on to give accurate information about the illness, the number of those affected, and where they lived.

In the wake of SARS, most nations, including China, have entered into a formal agreement to cooperate with the WHO along specific guidelines in the event of another outbreak with the potential for global contagion.

The harsh scientific reality is that such an outbreak will occur. According to epidemiologists, new strains of contagious pathogens are discovered on a regular basis, each with the potential to spread quickly from human to human.

There are several lessons from the SARS outbreak worth noting on its anniversary. Foremost is the essential value of early detection and reporting, with facts and advice that lead people to take appropriate precautions. Public health officers worry the warnings they issue may lead people to overreact, and they naturally worry warnings about possible pandemics that don't eventually materialize work to lessen their credibility.

The legacy of SARS is that it has helped us get past all that. As a milestone event, it awakened the world to the modern dangers of rampant contagion, and prompted the creation of a more effective global sentinel against SARS and its future cousins.