WASHINGTON — President Obama voiced hope yesterday that the swine flu virus will run its course "like ordinary flus" as officials reported more than two dozen new cases and scores more schools shut down.

The government issued new guidance for schools with confirmed cases, saying they should close for at least 14 days because children can be contagious for seven to 10 days from when they get sick.

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

"I'm optimistic that we're going to be able to manage this effectively," Obama said as he received an update on the federal response to the health emergency. At the same time, he emphasized that the federal government is preparing as if the worst is still to come so it won't be caught flat-footed.

Obama's fresh take on the flu scare — more intense in neighboring Mexico than in the United States but also present in some measure worldwide — came as the Centers for Disease Control and Prevention reported the virus has been confirmed in eight more U.S. states and seems to be spreading.

Confirmed cases have risen from 109 Thursday to 161 yesterday, the CDC said, with the flu now reported in 23 states, up from 11. A few states reported higher numbers, and the District of Columbia announced two likely cases. The U.S. death toll remained at one — the Mexican toddler who visited Texas 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 of the regular winter flu.

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

While emphasizing at a news conference that the closures to date represent a tiny fraction of the almost 100,000 schools in the country, Education Secretary Arne Duncan instructed teachers, parents and students to be prepared if their school does close.

ASIA GETS 1ST CASE

Key developments on swine flu outbreaks, according to Centers for Disease Control and Prevention, World Health Organization and government officials:

• Deaths: 16 confirmed in Mexico and one confirmed in U.S., a toddler from Mexico who died in Texas.

• A Mexican tourist visiting Hong Kong becomes Asia's first confirmed case. About 300 people were quarantined at a hotel where the tourists stayed.

• Continental Airlines Inc., US Airways Group Inc. and Delta Air Lines Inc. said they will reduce service to Mexico. JetBlue Airways Corp. canceled about a dozen flights over the next month to Cancun because they weren't full enough. Alaska Airlines said it was removing pillows and blankets from all of its 114 planes, and would disinfect and sanitize all of its planes during overnight maintenance.

• Hollywood studios have delayed plans to kick off the summer movie season in Mexico. Actors who had plans to promote films in the country, such as Hugh Jackman and Miley Cyrus, also are staying away for now.