LOS ANGELES - "Contagion" infected enough moviegoers to catch the top spot at the box office.

The Warner Bros. pandemic thriller directed by Steven Soderbergh and starring an A-list cast that includes Matt Damon, Kate Winslet, Jude Law and Gwyneth Paltrow coughed up $23.1 million in its first weekend, according to studio estimates Sunday.

The film's contagious opening marked the beginning of the fall movie season by exceeding the studio's estimates.

"I think Steven Soderbergh made a compelling movie that tapped into that fear that many of us have about illnesses, viruses and pandemics," said Jeff Goldstein, Warner Bros. general sales manager. "It's like a train or car accident. You can't look away. You prefer not to think about it, but when it's presented to you, you want to learn more."

Despite the breakout success of "Contagion," it was the lowest grossing weekend of the year so far for the film industry, according to Paul Dergarabedian, box-office analyst for Hollywood.com. Dergarabedian said that's typical for the weekend after Labor Day and expected business to pick up in the coming weeks as the Academy Awards race begins.

"There are some great titles that are on the way," said Dergarabedian. "I see several promising films - Oscar contenders like '50/50,' 'The Descendants' and 'Ides of March,' and even potential big moneymakers like 'Real Steel.'"

"The Help," the acclaimed DreamWorks Pictures drama distributed by Disney about black Southern maids speaking out during the civil-rights movement, slipped to No. 2 with $8.7 million after three straight weeks at the top, bringing its domestic total to $137 million.

"Warrior," the Lionsgate mixed-martial arts drama starring Tom Hardy and Joel Edgerton, punched up a $5.6 million debut in the No. 3 position. David Spitz, head of distribution for Lionsgate, said he expects "Warrior" to mirror the simmering success of "The Help."

"The film has gotten unbelievable reviews," said Spitz. "The audience reaction we're getting on the movie is consistent. People like the film. It's a slow burn. We think we're going to be in theaters for a long time."

Overseas, the family smash "The Smurfs" continued to dominate, pulling in $14.9 million to pad its international total to $321.2 million and its worldwide haul to $457.2 million. "Rise of the Planet of the Apes" again came in second internationally with $12.5 million, lifting its overseas take to $207.6 million and its worldwide total to $375.4 million.

Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters, according to Hollywood.com. Where available, latest international numbers are also included. Final domestic figures will be released Monday.

1. "Contagion," $23.1 million. ($2.1 million international.)

2. "The Help," $8.7 million.

3. "Warrior," $5.6 million.

4. "The Debt," $4.9 million. ($1.5 million international.)

5. "Colombiana," $4 million.

6. "Rise of the Planet of the Apes," $3.8 million. ($12.5 million international.)

7. "Shark Night 3D," $3.5 million. ($500,000 international.)

8. "Apollo 18," $2.9 million. ($425,000 international.)

9. "Our Idiot Brother," $2.7 million.

10. "Spy Kids: All the Time in the World," $2.5 million. ($425,000 international.)

Estimated weekend ticket sales at international theaters (excluding the U.S. and Canada), according to Rentrak:

1. "The Smurfs," $14.9 million.

2. "Rise of the Planet of the Apes," $12.5 million.

3. "Final Destination 5," $10.8 million.

4. "Friends with Benefits," $10.2 million.

5. "Captain America: The First Avenger," $8 million.

6. "Cowboys & Aliens," $5.5 million.

7. "Horrible Bosses," $5.3 million.

8. "Harry Potter and the Deathly Hallows: Part 2," $3.4 million.

9. "The Zookeeper," $3.3. million.

10. "Crazy, Stupid, Love," $2.9 million.