Quotes of the Day

There is no more powerful image of fear than a population gripped by plague. A novel flu virus exploded through Mexico last week, killing some 150, infecting hundreds more, and generating images of masked citizens and grim officials enumerating the latest toll. By April 29, the virus had spread to at least nine countries, leading health officials to raise the alert level and warn that a pandemic is imminent; the most recent influenza pandemic, in 1968, killed around a million people.

Fear thrives on uncertainty, and the current swine-flu virus has left health officials pondering crucial, unanswered questions: How easily is the virus transmitted between people? Why does it seem to be more lethal in Mexico than elsewhere? Can it be stopped? How long will it take to develop a vaccine?

Viruses spread faster than they used to. Our global financial system allowed America's subprime crisis to poison the world's economy. Another great symbol of globalization, jet travel, is capable of spreading a different type of infection — one that sickens not markets, but people.

But as health officials grapple with how to handle the crisis, whether to close borders and ground flights, it's worth remembering that, just as with our economic troubles, a retreat to protectionism will come at a high cost. A coordinated scientific response provides the best way forward, not panicked xenophobia.

One of the deadliest pandemics in human history — the Black Death of the 14th century, which killed roughly 25 million people in Europe — resulted in massive social dislocation and doubt in an omnipotent God, which some scholars think led to the intellectual ferment of the Renaissance. Cholera, when it came to Europe in the 1830s, led to the overhaul of public health and sanitation. Human vulnerability can paradoxically lead to the triumph of human confidence — the knowledge that progress can survive even the most dreadful diseases.

• EBEN HARRELL
• A flu virus spreads fear and illness around the world