WSU Virology

The industrial-size servings of food on a cruise ship with hundreds of passengers can be particularly worrisome, since once the virus enters the food it can spread rapidly. Food can also get more easily contaminated with the virus if it sits out for several hours, as is often the case with buffet-style meals.

And so many people being in one place eases the virus's spread. "In close quarters it doesn't get away, everything's concentrated," Zimring says.

The best defense against gastrointestinal disease, Zimring says, is to wash and sanitize your hands constantly

Over the past five years, an average of about 14 cruise ships a year have had outbreaks of diarrheal illness, and the culprit is almost always norovirus

The best way to avoid it is prevention, and the best prevention is hand washing.

The problem, he said, is passengers. “If Grandma is sick when she gets on, she’s going on the cruise anyway,” Dr. Vinjé said. “And that’s how the virus gets onboard. Then it lands on handrails and doorknobs, and the transmission continues.”

On Tuesday night, administration officials said the Pentagon would ask Congress to redirect $500 million from existing Defense Department funds to fight Ebola. The money is in addition to $500 million the Pentagon requested last week in redirected funds for both Iraq and Ebola.

The first possibility is that the Ebola virus spreads from West Africa to megacities in other regions of the developing world.

The second possibility is one that virologists are loath to discuss openly but are definitely considering in private: that an Ebola virus could mutate to become transmissible through the air.

The current Ebola virus’s hyper-evolution is unprecedented; there has been more human-to-human transmission in the past four months than most likely occurred in the last 500 to 1,000 years. Each new infection represents trillions of throws of the genetic dice.