This hardly seems the time to be arguing againstapocalyptic public health warnings, as the aftermath of Hurricane Katrina continues to unfold. But Katrina should not be a basis for heeding every dire prophecy. Given that we have limited resources to predict and protect ourselves, the hurricane instead is a reminder of the importance of distinguishing health warnings that are grounded in impending danger from warnings that are not.
Fear works best as a warning system when it is a response to dangers that directly threaten those who are afraid. In New Orleans, fear of the weak levees could have mobilized the public to put more pressure on the local and federal governments to fix them. But that didn't happen. One reason is that Americans tend to pour their fears into dangers that, however real, pose a relatively low risk for any individual—like terrorism, anthrax, smallpox, and now the avian flu.
The avian flu virus, or H5N1, has killed millions of birds in China and Russia, either directly or because they've been destroyed to prevent its spread. The virus has infected 112 humans, 57 of whom have died. Despite the small numbers, public health officials in Russia, Germany, and the United States—along with articles like this one and this one in Foreign Affairs—have loudly sounded the alarm: Avian influenza is about to transform into a massive human killer that could kill 50 million to 100 million people. In preparation, the Department of Health and Human Services has contracted for the production of 2 million doses of vaccine, with several million more on the way, as well as millions of doses of the anti-viral drug Tamiflu. This week, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called bird flu "a time bomb waiting to go off."
Yet the science behind all the worry is questionable. It rests on the unproven claim that the avian flu will develop exactly like the strain that caused the flu pandemic of 1918. A March 2004 article in Science showed that the 1918 flu—which infected close to a billion people and killed 50 million or more—made the jump from birds to humans through a slight change in the structure of its hemagglutinins, the molecules by which the virus attaches itself to body cells. This mutation allowed the virus to kill more World War I soldiers than weapons did, effectively ending the war when forces on both sides became too sick to fight.
The current bird flu, however, has a different molecular structure than the 1918 bug. And though it has infected millions of birds, there is no direct evidence that it is about to mutate into a form that would transmit from human to human. In isolated cases, food handlers in Asia have gotten sick, but that doesn't mean that a wildly lethal mutation is about to occur. As Wendy Orent points out in the New Republic, diseases that come from animals are often hard for humans to transmit. They lack the "essential characteristics" of virulent human infections—they're not durable, or waterborne, or carried by hospital workers, or transmitted sexually.
Even if the worst-case scenario does occur and the virus mutates, there is no current indication that it will spread the way the Spanish flu did in 1918. That disease incubated in the World War I trenches before it spread across the world, infecting soldiers who were exhausted, packed together in trenches, and lacked access to hygiene. These conditions were an essential breeding ground for the virus. Today, there is no way a huge number of people would be packed together in WWI-like conditions. Also, technology allows doctors to diagnose and isolate flu patients far more effectively.
Despite the lack of evidence about a huge avian flu pandemic, still we worry. That's a problem because fear causes stress, and stress is bad for your health. Numerous studies have shown the familiar link. The American Heart Association has emphasized a correlation between stress and overeating and stress and smoking, both of which lead to heart disease. A 2000 study in the journal Stroke of more than 2,000 men showed that those suffering from anxiety or depression were three times as likely to suffer a fatal stroke. A study in Psychosomatic Medicine showed that Israeli women with an expressed fear of terrorism had twice the level of an enzyme that correlates with heart disease.
The association between worry and physical disease means that doctors have a responsibility not to upset their patients unnecessarily. Yet many doctors increase worry by ordering tests with little explanation or deploying their assistants to relay a patient's test result as an impersonal statistic. In the same way that public health officials alarm the public about unlikely health threats, some doctors dispense information in a way that alarms their patients about diseases they don't have.
I recall one patient who was filled with fear about West Nile virus, SARS, mad cow disease, bird flu—everything that came down the media pike. He extended this worry to every test a doctor ordered for him. When I took over his care, it took me a long time to learn how to inform him without scaring him. Gaining his trust meant being careful not to sound false alarms.