Health professionals in Ontario have been debating a deeply subversive proposition as to how to deal with children and their risks from mosquito-borne West Nile virus.

"It has been suggested at a couple of meetings that I was at: 'Forget the kids. If they get infected earlier, if they get sick, they are not likely to have serious consequences, and they are protected for the rest of their life.' This has been the experiences of the endemic countries," said Colin D'Cunha, Ontario's chief medical officer of health.

The underlying rationale for the counterintuitive thinking is the very lumpy epidemiology of the disease. It is not as if children never come down with West Nile disease, but rather that they hardly ever do. In the United States, as of November, 2002, the Centers for Disease Control and Prevention reported that children under 9 made up only about 1 per cent of the 2,354 cases in which there was any kind of serious infection.

There were, in fact, more people over 90 who contracted the serious, brain-swelling form of the illness than there were under 10. The mortality statistics were even more skewed.

None of the 201 people who died in the United States was younger than 24.

In Canada the numbers are much the same.

Last year, of the 400 people in Ontario who came down with a serious form of West Nile disease, only six were younger than 20. Most were older than 10. None of the 17 people who died in Ontario -- there were 18 in the entire country -- was under age 20.

All of which leads to the argument that it could be better to be infected early with a mild case of the illness -- especially if that protection will last you for life. It is a way of thinking, point out experts, that often prevailed before vaccines were available. At measles or mumps "parties," parents tried to expose their children to these illnesses.

"There are quite a few examples of viruses that are much worse for adults than children. Mumps is one. You run the risk of sterility in adults which are postpuberty, which never happens in pre-puberty," says Earl Brown, a professor of virology at the University of Ottawa.

Rita Shahin, an associate medical officer of health in Toronto, said she agrees that a West Nile infection is not as serious in children as it is in adults. "The younger you are, the milder the illness," she said yesterday.

But Dr. Shahin's department is still warning parents to take precautions such as reducing standing water on their property "so that the whole family doesn't get exposed." And it is a good idea to avoid being outside at dusk and dawn when mosquitoes are most prevalent, and to wear long pants and use repellents when you're in an area where you might be bitten.

No one, in fact, is quite willing at present to tell people to let the mosquitoes do their damnedest to their kids. Part of this has to do with the still unknown nature of the illness.

In the Middle East, where it is endemic, the effects are quite mild. In North America, the effects are more dire. Maybe a natural immunity has developed in the Middle East, or maybe the virus has mutated and become more virulent here, says Prof. Brown.

"In the Middle East it is probably good to let children get it early and get more protection . . . but I would be a bit nervous about the logic of that here because the virus may be doing something we don't really yet know about."

When asked about the wisdom of letting nature take its biting course, Andrew Simor, head of microbiology at Sunnybrook and Women's College Health Sciences Centre in Toronto, first answered: "Good question. I don't have an answer to that one."

Then he backed up a bit. "I don't think parents should deliberately go out and infect their children -- that would be rash -- but I don't think that parents should be overconcerned because the risk is so small for children developing serious forms of the disease."

In everyone's mind, overriding what might turn out to be a long-term general health benefit is the fact that any sick child evinces a greater sympathy than that of a sick, aged, and infirmed adult.

"If only two nine-year-olds in the entire province become ill, their parents would say, 'You said it was 100 per cent safe and it wasn't.' You understand my challenge. What I am supposed to say to them?" Dr. D'Cunha said.