Illustration by Tom Bachtell

In early March of 2003, when SARS swept into Hong Kong from Southern China, the streets of one of the world’s most densely populated areas were practically deserted. Venders in kiosks sold face masks and hand sanitizer to anyone brave, or foolish, enough to leave home. The fear of a new highly contagious disease is understandable, and, with no effective treatment or vaccine for SARS, it was difficult to know what to do. The World Health Organization recommended that officials in the countries most affected warn people with a fever to stay off international flights. Hong Kong went further, using infrared scanners and thermometers to take the temperature of more than thirty-six million passengers as they arrived. Nineteen hundred and twenty-one of them had a fever, and forty were admitted to the hospital. None developed SARS. (Canada and Singapore also scanned arriving passengers. Neither country found anyone with sars.)

Last week, the Obama Administration announced that, at five major U.S. airports, passengers arriving from Liberia, Guinea, and Sierra Leone will be checked for fever. That measure isn’t likely to be any more effective at detecting the Ebola virus than it was at finding SARS. Thomas Eric Duncan, the first person to receive a diagnosis of Ebola in the United States, died last Wednesday, in Dallas. But before he left Liberia, as part of a routine scan at the Monrovia airport, a technician who had been trained by the Centers for Disease Control and Prevention took his temperature with a type of infrared thermometer that had been approved by the Food and Drug Administration. Duncan had no fever, which isn’t surprising, as it can take as long as three weeks for Ebola to cause symptoms (and until people develop symptoms they are not contagious). Still, on Wednesday, Senator Charles E. Schumer, of New York, said, “Taking temperatures and learning more about passengers coming here from West Africa will provide another necessary line of defense against this epidemic. When it comes to Ebola, you can’t be too careful. As we saw in Dallas, all it takes is one case to discombobulate an entire city.”

Actually, all it takes to discombobulate a city is a few irrational decisions and some irresponsible statements. Several politicians, like Governor Bobby Jindal, of Louisiana, have turned the epidemic into fodder for their campaign to halt immigration. Jindal, and others, have suggested that we ought to simply close our borders to people coming from West Africa. That would only increase the isolation of countries that have already been devastated and make it harder to deliver essential aid there. As Bruce Aylward, the assistant director general of the W.H.O., has pointed out, travel bans make the world sicker, not safer. He said recently, “The more difficulty you have with travel and trade, the harder it is to have an appropriate response.” He added, “which means this disease is getting more and more ahead of us.”

Fear is not a weakness; it’s how people respond to danger. Unless it is calibrated properly, however, fear quickly turns into panic, and panic moves faster than any virus. Diseases that get the most attention and cause the greatest anxiety are rarely those which claim the most lives. Malaria, tuberculosis, and H.I.V. have killed hundreds of thousands of people this year. Fewer than a thousand people died in the 2003 SARS epidemic, but a report by the National Academy of Sciences notes that its cost to the global economy—not only in medical expenditures but in lost trade, productivity, and investment—was almost forty billion dollars.

At least four thousand people have already died of Ebola, the economic impact of the epidemic has been calamitous, and every day the numbers get worse. But we need to stop acting as if the tragedy unfolding in Liberia, Guinea, and Sierra Leone could happen here on anything like the same scale. There will be more cases of Ebola in the United States, but unless something remarkably unlikely develops, such as a mutation that makes it easier for the virus to spread, the epidemic can be stopped. Ebola is difficult to contract, and although viruses mutate constantly, once they are established in humans they do not generally alter their mode of transmission.

That message is not getting through. According to a Harris poll taken just before Duncan’s diagnosis, forty per cent of Americans believed that Ebola represented a major or a moderate threat to public health in the United States. Thirty-seven per cent thought that the H1N1 influenza epidemic of 2009 posed a similar threat. The two outbreaks are not comparable. H1N1 infected about twenty per cent of the world’s population, including sixty million Americans. A catastrophe was averted owing solely to a biological fluke: the death rate of those infected was unusually low—there were more than twelve thousand fatalities in the U.S., but that is far fewer than die from the flu in most years.

Our response to pandemics—whether SARS, avian influenza, MERS, or Ebola—has become predictable. First, there is the panic. Then, as the pandemic ebbs, we forget. We can’t afford to do either. This epidemic won’t be over soon, but that is even more reason to focus on what works. Liberia, Guinea, and Sierra Leone all need more money, more health-care workers, and more troops to help coördinate relief efforts. In the short term, the only way to halt the epidemic is with better infection-control measures. In Senegal and Nigeria, two countries where poverty and health problems are pervasive, the most basic such measures—contact tracing, quarantine, and proper protections for health workers—seem to have had a positive effect. (Part of the success in Nigeria is also due to the fact that officials made an enormous effort to keep the virus out of Lagos, a city of twenty million people.)

We also need to take better advantage of our scientific tools. Advances in molecular and synthetic biology have begun to provide a sophisticated understanding of the genetic composition of viruses. We are increasingly able to make vaccines by assembling synthetic proteins as if they were molecular Legos. Rob Carlson, the author of “Biology Is Technology,” who has written widely about genetic engineering and vaccine development, says, “We could have pushed the development of a synthetic Ebola vaccine a decade ago. We had the skills, but we chose not to pursue it. Why? Because we weren’t the people getting sick.” One day, a virus that matches our sense of doom may come along. Until then, we will need to rely on data and evidence—not theatrics or fear. ♦