There were plenty of computer glitches when millions of Americans went online to check out their options for affordable insurance policies on the new health care exchanges that opened for business this week. It was frustrating, but it was also an indication of overwhelming interest that exceeded all predictions.

In the first three days, there were 8.6 million unique visitors to the federal government Web site for health care exchanges, far more than had ever signed on at one time to a popular Web site serving Medicare patients. In New York, the state-run exchange had an astonishing 30 million visits in the first two days, although a large share almost surely consisted of repeat visits by people who were blocked by balky computer systems.

Earlier surveys had shown that most Americans were unaware that the exchanges would open on Oct. 1 and ignorant of what the health care reform law could provide for them. Many thought it was still just a proposal, not a law. (Congressional Republicans who have shut down the government over their demands to defund and weaken health care reform may have inadvertently fanned interest in exchanges by putting them in the news.)

Neither federal nor state officials were willing to say how many people actually enrolled in a health plan the first week, but the numbers are surely low. People need time to ponder their choices, and the computer problems haven’t made it easy. But the start-up problems are sure to be smoothed out as enrollment for coverage in 2014 goes on for the next six months. As federal officials stress, this is not a sprint but a marathon.