U.S. officials advised Americans against most travel to Mexico on Monday as a swine flu virus that began there spread to the United States and beyond. With 40 cases now confirmed in the United States, President Barack Obama said there was reason for concern but not yet “a cause for alarm.”

Dr. Richard Besser, acting director of the Centers of Disease Control and Prevention, said that so far the disease in the United States seems less severe than the outbreak in Mexico, where more than 1,600 cases have been reported and where the suspected death toll has climbed to 149. No deaths have been reported in the U.S, and only one hospitalization.

“I wouldn’t be overly reassured by that,” Besser told reporters at CDC’s headquarters in Atlanta. He raised the possibility of more severe cases in the United States.

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Rihanna and Chris Brown seemed the happy couple just last month.

It started with a text.

The explosive fight that landed sultry singer Rihanna in the hospital ignited when singer Chris Brown got a text message from another young woman, a source said.

“He got a booty call. He got a text. Rihanna saw it and she got upset. They started to argue. She got out of the car. He wanted her to get back in, so he grabbed her,” the industry source said. “She pulled away. That’s when she’s told people he hit her.”

The Barbados-born beauty had “visible injuries” when cops arrived, and she’s been cooperating with the investigation ever since, while freezing out Brown.

“Chris has been trying to contact her. So far she hasn’t taken his call,” the music business source said. “Her family is on their way to be with her. She has some close girlfriend looking after her.”

The source scoffed at reports that the fight erupted after a jealous Brown scolded Rihanna for spending time with producer Timbaland at a pre-Grammy party.

Cops and sources say the two were driving a rented Lamborghini on a ritzy street south of Rihanna’s pad in the Hollywood Hills early Sunday when they quarreled, parked, got out and “the argument escalated.”

Cops responding to a 911 call found the “Umbrella” singer with a split lip and contusions on either side of her forehead, according to People.com.

“She looked distraught and in a lot of pain. Her eyes were closed because she was looking down,” a police source who saw photos told People.com.

Rihanna also reportedly had bite marks on her hand and was treated at Cedars-Sinai Medical Center.

Cops delivered their case to prosecutors Tuesday, but the district attorney sent them back to the drawing board.

“LAPD did present a case this morning and we have asked for further investigation,” DA spokeswoman Jane Robison said.

Robison wouldn’t describe the holes that prosecutors want plugged.

A legal expert said prosecutors generally ask for an overabundance of “witness work” in cases like this because victims often lose their nerve when it comes to trial.

“These cases are often stymied by the refusal of victims to testify,” said attorney Alexandra Leichter, a Beverly Hills-based private arbitrator. “If witnesses saw the victim before the attack, witnesses heard the screams and then cops came and she was bloodied, then the circumstantial evidence could be enough to convict.”

The Daily News spoke to a witness Tuesday who heard the raucous fight explode outside her house: “I heard the screaming. It was loud,” the homeowner said.

“In my opinion, either [the cops] have conflicting stories and not enough evidence, or the DA is debating whether to file this as misdemeanor or felony battery,” said defense attorney Steve Cron. “If you have a scratch or a bruise, that’s more in the realm of misdemeanor. If you have a cut that requires stitches, bruising showing multiple blows, a broken bone or a chipped tooth, that’s more felony.”

Brown, 19, has kept a low profile since he was booked on a felony criminal threats charge and released on $50,000 bail. His attorney Mark Geragos did not return calls seeking comment.

Singer Kanye West, who toured with Rihanna last year, said he was “devastated” by word of the alleged abuse.

“All I will say is, it’s so devastating. I feel like, just as a person, I don’t care how famous she is, or even if she worked at McDonald’s, that should have never happened,” West told Ryan Seacrest during a radio interview. “It should never come to that place.”

The new series’ pilot was penned by producer Rob Thomas, who resigned as creator to make way for Gabe Sachs and Jeff Judah, who produced a revised version of his script.

The new “90210″ uses some of the same sets as “Beverly Hills, 90210″ such as the high school and ‘the Peach Pit’, and much like the original show, 90210 follows the move of a family [parents Debbie and Harry Wilson, their daughter Annie and adoptive son Dixon] from Kansas to settle in Beverly Hills.

A graduate of Beverly Hills High, Harry comes back to Beverly Hills both to look after his mother Tabitha and to work as the Beverly Hills High school principal. The family struggles to adjust to their new lives; daughter Annie has a hard time balancing romances and friendships as well as popularity and identity, while their adopted son Dixon has a hard time finding peace with issues of his adoption and heritage, while in the meantime parents Harry and Debbie hit a road bump when they discover that Harry has a son from a former high school sweetheart.

Harry’s high school sweetheart, Tracy Clark, has a daughter of her own, Naomi Clark. Naomi and Annie alternate between enemies in a love triangle and sister-like sentiments as the plot thickens.

Naomi’s best friend, fallen starlet Adrianna Duncan battles a drug addiction. This causes her a great deal of trouble when Harry decides to clean the school, with the help of an undercover cop disguised as a student: Kimberly McIntyre.

Navid Shirazi is the head of the school’s paper and Dixon’s best friend. He gravitates towards Adrianna and helps with her addiction.

The creators of the new series sought to reinvent “90210″ through using current and timely issues in their storyline and subplots, promising a timelier product, delivered in a more powerfully realistic fashion.