Nurse Kaci Hickox was quarantined at a New Jersey hospital because she had contact with Ebola patients in West Africa. (University of Texas at Arlington via AP)

ONE OF the profound challenges of our age is how to evaluate risk from complex threats. At one level, experts provide scientific facts about, say, the transmissibility of a disease, and they can quantify the prospects for contagion. At another level, human emotions measure risk with irrational but powerful gut feelings. In a 1987 essay in Science magazine, Paul Slovic of the University of Oregon cautioned that emotions and science must be given equal weight. He wrote that “there is wisdom as well as error in public attitudes and perceptions.” His message was that, in communicating and dealing with perceptions of risk, fears and dread need to be considered as carefully as precise measurements by experts.

Dr. Slovic’s advice is relevant to the debate about Ebola virus disease and the possibility of its spread in the United States. People are worried. To some extent you can blame alarmist news coverage and exploitative politicians. But that does not mean that everyone’s worry should be dismissed. Rather, the fears need to be taken into account as well as the science — meaning decision-makers must be vigilant, transparent, credible and candid. Maintaining public confidence is a big part of protecting public health.

The decision over the weekend to quarantine a nurse, Kaci Hickox, who had returned to New Jersey from working in Sierra Leone with the charity Doctors Without Borders, overreached. Ms. Hickox had tested negative for Ebola, and her confinement was brusque. It made good sense for New Jersey to backpedal on Monday and permit her to go home under carefully controlled circumstances.

It also made good sense for Dr. Craig Spencer to check himself into a New York City hospital after feeling symptoms last week following his return from West Africa. Dr. Spencer had been out and about in the city for two days prior to the symptoms emerging — jogging, walking the High Line, bowling. He traveled on three subway lines and in an Uber car. He has since tested positive for Ebola. This makes people nervous — understandably so.

The right answer is to protect the public without overreacting. Mistakes made in the Dallas hospital ought to be a warning and a lesson, and it seems to us that they are being taken as such. The decisions adopted by Maryland and Virginia on Monday — to screen and monitor those returning from the Ebola-stricken region of West Africa, and to ask some to stay home or away from public places — are prudent and reasonable. The experts have repeatedly explained that Ebola does not spread like the flu; transmission requires the transfer of bodily fluids. That’s the science. But emotions count, too.

The most serious shortcoming in the global response to Ebola has been a lack of health-care workers where they’re most needed. Those like Ms. Hickox who volunteer for this duty deserve our utmost respect and thanks, and proper care upon return. They must not be stigmatized or mistreated even in understandable moments of dread, and irrational steps that could discourage others from volunteering must be avoided.