(AP) - President Barack Obama voiced hope Friday thatthe swine flu virus will run its course "like ordinary flus" asofficials reported more than two dozen new cases and scores moreschools shut down.

The government issued new guidance for schools with confirmedcases, saying they should close for at least 14 days becausechildren can be contagious for seven to 10 days from when they getsick. That means parents can expect to have children at home forlonger than previously thought.

The Education Department said that 433 schools had closed,affecting 245,000 children in 17 states. That was about 100 moreschools reported closed than reported on Thursday.

Major U.S. airlines, meanwhile, announced plans to curtailflights into flu-ravaged Mexico.

"I'm optimistic that we're going to be able to manage thiseffectively," Obama told reporters as he received an update fromhis Cabinet on the federal response to the health emergency. At thesame time, he emphasized that the federal government is preparingas if the worst is still to come so that it won't be caughtflat-footed.

Obama's fresh take on the flu scare - more intense inneighboring Mexico than in the United States but also present insome measure around the globe - came as the Centers for DiseaseControl and Prevention reported the virus has been confirmed ineight more U.S. states and seems to be spreading.

Confirmed cases have risen from 109 Thursday to 141 Friday, theCDC said, with the flu now reported in 19 states, up from 11.Separately, a few states reported slightly higher numbers, and theDistrict of Columbia announced its first two probable cases. TheU.S. death toll remained at one - the Mexican toddler who visitedTexas with his family and died there.

The most recent onset of illness was Tuesday, CDC said,indicating a continuing spread, though no faster than the rate ofthe regular winter flu.

"We think the cases do continue to occur," said CDC's Dr. AnneSchuchat. But CDC also said the new swine flu virus lacks genesthat made the 1918 pandemic strain so deadly.

Obama said it wasn't clear whether the flu would be more severethan others before it, and he said the swine flu is a cause forspecial concern because it is a new strain and people have notdeveloped an immunity to it.

The CDC added the following states to its list of those withconfirmed cases: New Jersey with five cases, Delaware with four,Illinois with three, Colorado and Virginia with two, and Minnesota,Nebraska and Kentucky each with one.

CDC previously had confirmed cases in New York, Texas,California, South Carolina, Kansas, Massachusetts, Indiana, Ohio,Arizona, Michigan and Nevada.