Immigrants and their families gathered at rallies across the country on Friday to push for changes to U.S. immigration policy, but as a swine flu outbreak continued to spread, attendance at some events was smaller than organizers had hoped.

The area hardest hit by the swine flu is Mexico, also the native home of many rally participants. There were no immediate reports of canceled events, but Juan Pablo Chavez, a community organizer for the Florida Immigration Coalition, said he and others were monitoring the situation and in close contact with state health care officials.

"If they tell us to halt the events, we will cancel immediately. But for now, we are simply asking people who are sick not to come out," Chavez said.

Organizers are seeking to channel the political muscle Hispanics showed last fall in support of then-presidential candidate Barack Obama. They hope that energy will jump-start stalled efforts to pass an immigration law that provides a path to citizenship for the estimated 12 million illegal immigrants living in the United States.

They had hoped crowds would equal or exceed those of last year, down from the 2006 turnout, when a stringent immigration bill poised to pass in Congress drew massive protests.

Thousands were expected at events in Houston, Los Angeles, Chicago, New York and other cities — mostly in the late afternoon, when workers finished their shifts. But early reports suggested turnout would be far lower than in previous years.

In Chicago, rally-goers chanted and carried signs demanding citizenship opportunities as they gathered at Union Park, and unfurled a banner of flags stitched together from countries across the globe. Organizers said they expected about 15,000 at the event, but the crowd appeared to be much smaller.

Waukegan resident Armando Pena said he was disappointed that more people didn't turn out and blamed the low numbers on a combination of the flu and tough economic times.

"The economy is so bad they don't want to lose their jobs," said Pena, who organized a contingent of about 50 people.

A line of about 225 marchers made their way down the main thoroughfare in New Jersey's largest city Friday, stopping to recite chants and gather for a vigil in front of the federal immigration building in Newark.

The marchers were led by dozens of Latin American immigrant ice cream vendors wheeling pushcarts decorated with bright umbrellas and covered in signs. One read "Say Reform, Not Raids."

In Miami, activists planned to gather downtown across from the turquoise waters of Biscayne Bay for a rally and march. They also want temporary protection for the state's large community of Haitian immigrants, whose native island has been devastated in recent years by hurricanes and floods.

In New York City, participants were set to gather in Union Square. Immigrant, labor and faith communities gathered under a light drizzle at Madison Square Park.

Activists' hopes have been buoyed with Obama in the White House and a Democratic-controlled Congress, in part because they believe the Hispanic vote, about two-thirds of which went to Obama, helped flip key battleground states such as Colorado and New Mexico. Many Hispanics strongly back comprehensive immigration reform, and they believe Obama owes them.

The White House announced this week that it would refocus its resources on prosecuting employers who hire illegal immigrants. And a Senate Judiciary subcommittee took up immigration this week for the first time in the new Congress.

But many immigrants are wary. They say that the immigration raids that grew common under the Bush administration have continued, and not stopped, since Obama took office.

In Colorado, a march was planned for Saturday in Greeley, a rural town 60 miles north of Denver, and the site of a 2006 federal raid at a meatpacking plant, in which 261 undocumented workers were detained.

Greeley is also the place where dozens of illegal immigrants were charged with identity theft last year for filing taxes using false or stolen social security numbers. County judges have since ruled tax records are confidential and authorities were wrong to seize them, but the decisions will be appealed.

"Greeley is the microcosm," said Alonzo Barron Ortiz, an organizer with the group Al Frente de la Lucha, which chose Saturday so workers wouldn't have to miss work.

Miami-Dade College student Felipe Matos, a native of Brazil, said he hoped the marches would raise awareness among those not directly affected about the impact of deportations on families.

"A lot of time you hear the numbers, 11 million people, but you don't see the faces, you don't hear the stories of the people," he said.

Matos said many of his friends feel emboldened by what they see as their role in the November election.

"Young people decided to go out and vote and get other people to vote," he said. "Now people feel empowered to make a difference and change policy."