It was only afterwards that James Goins began to wonder at the narrowness of his son's escape.

The doctors couldn't tell him what was wrong with 16-year-old Aaron even as the youth's temperature surged and Goins watched helplessly as his son's suffering worsened.

"I couldn't even touch my son he was so hot. I couldn't pick him up. His muscles were seizing up on him. He couldn't move. He had a fever of 102. He was throwing up, and diarrhoea. He screamed out when I touched him. My wife was freaking out. I thought I was going to lose my son. It's the hardest thing in the world."

At that point Goins, the director of an arts foundation in California, called an ambulance.

"The doctors said maybe it was appendicitis. They said he might have to have immediate surgery. He was in so much pain he was on morphine, for god's sake."

The hospital eventually concluded that it wasn't appendicitis after all. "They didn't have any answers. They just said it was a very bad flu. In their words 'a wicked flu'," said Goins.

The doctors may have been closer than they realised.

Aaron slowly recovered while his father still worried about what had struck his son down. Then the teenager returned from school with a possible answer.

"His biology teacher was the one who pointed it out. He said Aaron had to have had the swine flu," he said.

The reports of swine flu had only just begun to come in, first from Mexico and then parts of the US, including California.

"When we looked at it, it was exactly the same symptoms. It made sense. This wasn't any normal flu," said Goins.

Aaron hasn't been to Mexico but his home town of Palmdale has a large Latino population some of whom regularly travel back and forth across the border.

"I suppose it could have been passed on at school or the art institute. Other children in the area have been sick but not as bad as Aaron," said Goins. "This whole thing was absolutely horrendous."

Goins could be wrong, although the doctors cannot offer any other explanation for Aaron's illness. But a lot of parents are wondering these days.

There is no sense of panic in the US. The number of infections by swine flu remains small and many people remember the failure of the avian flu scare to materialise into mass casualties.

But there is growing unease among some over where the latest crisis might lead and, at times, doubts about the government's assertions that it can handle it.

The declaration of a health emergency, President Barack Obama's plea to congress for $1.5bn (£1.02bn) to deal with the disease and the admission by the head of the Centres for Disease Control that deaths will surely come, have parents from California to New York checking their children and themselves.

The largest cluster of swine flu infections in the US is in one, and possibly three, New York City schools. The city's health commissioner says the total number of infected children could run into the hundreds.

Sophia Goumakos, 17, was among those who became sick at St. Francis prep school after a trip to Cancún. Her symptoms were relatively mild, a sore throat and a temperature. Her mother, Peggy, hauled her off to Long Island Jewish hospital. Reports about swine flu were by then taking over the news bulletins.

"I couldn't text anyone. I couldn't watch TV," Goumakos told the New York Post.

The hospital concluded that Sophia did not have swine flu. But the young woman's symptoms only grew worse and her mother sent the laboratory test to the city health department.

On Sunday evening, it told the Goumakos that Sophia had contracted the disease. School friends and other parents have been in touch, out of concern but also no doubt out of the sense of solidarity that fear can bring.

"Everybody's made such a big deal," said Peggy Goumakos. Aaron Goins recovered and Sophia Goumakos is receiving treatment.