The Centers for Disease Control held a press conference Tuesday to announce that for the first time, ever, a patient in the United States has been diagnosed with Ebola. Acknowledging that Ebola "can be scary," CDC Director Tom Frieden described the actions officials have already taken to ensure no one else is infected—such as quarantining the patient in a Dallas, Texas, hospital and seeking out anyone who might have been in direct contact. "I have no doubt that we will control or contain this case of Ebola so it does not spread throughout the country," Frieden said.

It was a textbook response to public health news that has the potential to incite mass panic.

In fact, the CDC was following its own textbook—that is, the agency's Crisis and Emergency Risk Communication. One passage even uses Ebola as an example, advising, "Avoid playing worst-case scenario. Stick to the known facts. If there is no information suggesting an outbreak involves Ebola, avoid mentioning it. If the facts are not known, don’t fall into the 'what ifs.' Instead, describe the steps you are using to get the facts and help the audience deal with the uncertainty while all the facts are uncovered. Speculation weakens credibility and may create needless anxiety."

All good advice, which the CDC appears to have been following precisely. That patient was admitted to a hospital on September 28, and the CDC only gave a press conference on the 30th, after it confirmed the patient indeed has Ebola.

Officials communicate health threats in this way to prevent unhelpful, if natural reactions to fear and uncertainty.

"Great uncertainty without guidance and support increases unhelpful behavior in a crisis,"  Dr. Barbara Reynolds, now director of public affairs at the CDC, wrote in a 2011 blog post. She notes that panic itself is a rare behavior. "From a psychological point of view, panic is best used to explain a behavior that is irrational or counter to a person’s survival."