The New Killer Diseases: How the Alarming Evolution of Germs Threatens Us All

The story of SARS (severe acute respiratory syndrome)--why the virus spread so rapidly, and how the international community responded--is a powerful, cautionary tale about the thorny challenges we must grapple with as we confront a growing number of infectious microbes that are evolving at an alarming rate. In the chapters that follow, we explore these pressing issues, introducing all the vital information the public needs to know about how best to protect ourselves against these diseases, as well as measures the medical community and our government should be taking to fight them. SARS has unfortunately established a significant foothold around the world, and we must expect that it will continue to spread--though less rapidly--and also to evolve, just as West Nile virus, Lyme disease, and other recently emerged scourges have done. SARS is one of the fastest spreading and most virulent new diseases the world had seen in some time. Yet we might well face an even more deadly foe before long, and we must learn the lessons the SARS saga holds for us.

The good news witnessed during the SARS outbreak is that the world community has made great progress in its ability to track and combat emerging diseases. But the outbreak also brought into stark relief a number of weaknesses in our defenses and a set of tough questions we must address. When a new disease has broken out, can we depend on all nations to share information readily and to take the necessary steps to limit the spread? What are the most effective means of containing a new disease, and what are the acceptable limits of government control? In the case of SARS, did the World Health Organization and national health authorities act fast enough to warn people of the danger, or did they go too far in some countries, provoking unnecessary panic? What social costs are we willing to pay in order to respond with the vigilance required? Do we need more disease detection at airports and other points of entry, or tougher quarantine laws? What will the ripple effects on the world economy be? And most fundamentally, how can we best determine that a new disease has appeared, and why it spreads so much more rapidly in one locale versus another?

The World Health Organization (WHO) sounded the SARS alarm on March 15, 2003, declaring the disease a worldwide health threat because it was spreading so far, so fast. In less than seven days after the first case had been identified in Hong Kong, dozens of people, many of them health care workers, had come down with it there, and patients had also been diagnosed with SARS in Hanoi, Vietnam, and in Toronto, Canada. The fact that the disease had made it all the way to North America so fast alerted the WHO that this outbreak might well become a global epidemic.

The first symptoms of the disease were fever and dry cough, and in some people muscle aches, sore throat, and diarrhea. These symptoms mimic those from influenza or the common cold, so at first patients were unaware of how serious their illness was, and many didn't go to see a doctor. However, SARS quickly progressed to pneumonia in some patients, or caused such difficulty in breathing that doctors had to hook some up to mechanical ventilators. Those who succumbed were killed when, as in other pneumonias, the heart or other organs failed due to the stress of not getting sufficient oxygen.

More than any other recent disease, SARS traveled like wildfire because of "superspreaders," people infected with a disease who pass it on to an inordinate number of others. In Singapore, for example, one young woman who checked into a hospital after returning from Hong Kong infected twenty nurses and patients, while two other young women who had also come back did not pass on the germ to anyone. Evidence for superspreaders is rare in history. Occasional AIDS patients and TB carriers may have fit this label, and certain people exposed to any ailment such as flu are more contagious than others, but the SARS superspreaders stood out as flagrant examples. Ironically, it was the unusual spread of SARS from a single patient to many of that same person's doctors and nurses that first alerted the medical community this disease was different from other pneumonias. Indeed, it was the stunning specter of large numbers of hospital workers falling gravely ill in several of the treatment centers where patients were being examined that prompted the WHO to issue a global warning.

As of early May it was still unclear if the superspreaders were somehow different from other patients, or if they were just at the bad end of a spectrum of infectivity. They are a topic of great interest, but little is known yet. Do they have a differently mutated form of the virus?