BOSTON -- After the fear had ignited a fire, after the Rays were burned out of their home town, the people of Arcadia, Fla., started poking around the embers of their town's reputation. They were trying to see what could be saved.

The Citizens Against AIDS in Schools, the very group that had opposed the admission of the three Ray boys, all hemophiliacs, all infected with the AIDS virus, began collecting clothes and bikes and food. The priest at the local church called on his parishioners to "look into their own hearts."

A schoolteacher, the mayor's wife, who had sent her own 10-year-old to private school tried to explain herself to a reporter. "There isn't anyone who doesn't feel sympathy for the Ray children," said Sue Ellen Smith. "But there are too many unanswered questions about this disease, and if you are intelligent and listen and read about AIDS, you get scared when it involves your own children because you realize all the assurances are not based on solid evidence."

It was easy to dismiss the people of Arcadia as ignorant, to moralize about a whole town, to see the story through the violent prism of the arsonist. But, in fact, Smith did what most people do. She tried to assess risks.

Using her own personal balance sheet, this mother listed her fears, the "unanswered questions," the experts' "assurances" and the "evidence." Then, in the face of uncertainty, she chose, or so she believed, to put her son out of harm's way.

I don't agree with Smith's assessment or action. Nor do those parents who sent their children to school with the Ray boys. Nor do the parents in that other Arcadia, in Indiana, where Ryan White, a 15-year-old with AIDS, started high school without incident. But I do understand the desire for absolute safety and the distrust of experts.

In the face of a disease like AIDS, we all become risk assessors. We want guarantees, and all we can get is odds.

No responsible scientist says today that it's impossible to transmit the AIDS virus in school. If one of the Rays bled, if a classmate with open sores touched that blood, he could conceivably be infected with the virus. Three health workers came down with AIDS in similar ways.

Such risks are remote -- perhaps infinitesimal -- but they exist. How are we to think about them?

Lester Lave, past president of the Society of Risk Analysis and a professor at Carnegie-Mellon University, has spent most of his work life trying to figure out how people make decisions about risk. We factor in anxiety about the issue, confidence in the experts. If the chance of catching any lethal disease were one in a billion, he notes, we would all dismiss the risk. If the chances were one in two, "we would all run for the hills."

"Most of us don't spend time worrying about minimal risks -- being hit by a meteor or by lightning," says Lave. It is uncertainty that is most confusing. "In any society, new risks arise. Those fears will lead sensible people to be 'prudent' and others to fly off the handle. My prediction is that it will be a good long time before we manage to settle this issue."

Sue Ellen Smith's son incurs a much greater risk riding in a car to his new private school than going to class with the Rays. The risk from these three boys, none of whom has active AIDs or behavior problems, is almost nonexistent. The uncomfortable "almost" is what we have to live with.

"If this were a disease that parrots carried and this year three parrots were found to have the virus, I wouldn't hesitate to have the birds removed no matter how small the risk," says Harvey Fineberg, dean of Harvard's School of Public Health. "The problem is that you're dealing with other lives. You can't balance a clear and present harm done to three youngsters against infinitesimal risk."

That is what happened in Arcadia, Fla. The risk of infection became the reality of community violence and disruption. Here is another entry into the annals of our risk anxiety. Not the last. Not by a long shot.