"They're finding bubonic plague on the subway!" a friend recently said to me. "How afraid should I be?" Some subway riders are scared.
The discovery that a wide range of germs lurk in the subway should motivate us to change our behavior. But not in the ways we may think.
A major myth exists: that getting exposed to a germ inevitably causes disease. In fact, it sometimes does; but not always. Many factors are involved.
I learned this forcefully several years ago when I studied a disease called kuru in Papua New Guinea - caused by infectious proteins called prions, which also cause bovine spongiform encephalopathy or "Mad Cow" disease.
Kuru spread through cannibalistic rituals. The woman had no other source of meat in their diet. When someone died, the women and their young children consumed the body in acts of mourning. "This way," one woman told me, "I will always have part of my mother inside of me."
But I interviewed villagers who had been at several feasts and had not gotten sick. When researchers first discovered the disease, they thought it might be genetic, since some areas had the epidemic, while others did not.
However, Dr. Carleton Gajdusek and his colleagues at an NIH lab, where I worked several years ago, exposed animals to brain tissue from patients. At first, nothing happened. But after several years, the animals became ill and died, showing that the disease was in fact infectious.
But not all animals got sick.
Starting in the 1990s, when people began to die of Creutzfeldt-Jakob Disease, acquired from "mad" cows, some epidemiologists argued that hundreds of thousands of Britons would die of the disease every year. Based on my experience in New Guinea, I argued otherwise.
Thus far, there have been less than around 200 deaths.
If someone with the flu sneezes in a classroom, not everyone gets sick; and those that get sick vary in when and how severely they get ill. Many infectious diseases depend on the dose of germs, and the immune system of the host. That's why we are more likely to get infections when we are tired and rundown. Being exposed on your hands to a tiny amount of a bacteria or virus will by no means get you sick.
However, every day, whether we ride the subway or not, we should still be careful. We touch surfaces and then rub our noses and eat with our fingers -- all of which can potentially spread our germs.
Importantly, we should be careful to avoid not only getting infections, but spreading them. Our mothers and grandmothers were right: wash your hands before eating, and cover your mouth when you cough or sneeze. If you feel sick with the flu, stay home, and drink fluids, rather than go out and infect others.
I am always struck that in Japan, anyone on the subway who has a cold wears a paper face mask. We should do the same, but alas we don't. If we did, perhaps fewer of us would get sick every year. But people are afraid that if they wear a mask, others will see them as a pariah. We need to overcome this stigma.
The discovery that germs lurk in the subway should motivate us to be healthier, and remind us of just how germs do and don't spread, and what we can do to avoid them. We should stay healthy, get enough sleep, exercise, avoid rubbing our noses,
We should also get a flu shot every year, yet many people don't. Perhaps ironically, the "scare" about germs on the subway also comes at the same time that countless people are refusing vaccines that have been proven to prevent measles. We don't see germs, so often don't think about them when we should.
The discovery of germs in the subway is important and should definitely alter our behavior. It should be a wake up call to how vulnerable we all are, and how careful we all should be with each other -- in both directions.