Editor’s Note: Go inside the chaos and courage of the September 11, 2001, attacks in New York in “9/11: Fifteen Years Later,” airing Sunday, September 11, at 8p ET

Story highlights

Several terrorist attacks have occurred on US soil in the past five years

Americans say they experience more anger and fear when they think about what happened 15 years ago

Washington CNN  — 

Fifteen years after the 9/11 attacks, Americans are increasingly worried that terrorists will strike in the days around the anniversary, and they are more likely than five years ago to feel fear and anger when they think about what happened that day, according to a new CNN/ORC Poll.

Half of Americans say that acts of terrorism in the US in the days around September 11 this year are at least somewhat likely, up from 39% who felt that way around the 10th anniversary of the attacks in 2011.

The time between these two anniversaries has seen the rise of ISIS and several high-profile terrorist attacks both in the US and abroad. On US soil, those include the Boston Marathon bombing in 2013, an attack on a military recruiting center in Tennessee and a mass shooting in San Bernardino, California, by a couple who had self-radicalized. In Europe, terrorists have struck an airport in Brussels, several sites around Paris and a Bastille Day celebration in Nice in the last year alone.

Read the poll results

The increased concern about new attacks comes as Americans say they experience more anger and fear when they think about what happened 15 years ago on 9/11. About three-quarters say they feel anger when they look back, about on par with the share who felt angry on the fifth anniversary but significantly above the 62% who said so at the 10th anniversary. A smaller share, 40%, say they feel fear when they think about 9/11, but that too is up from five years ago. Then, just 30% said they felt fearful when considering the terrorist attacks, a figure that stood at 44% in 2006.

The percentage of Americans who think about 9/11 frequently or have visited the site where the twin towers once stood in New York City has stabilized since the last major anniversary: 22% say they’ve been to Ground Zero, about the same as the 21% who said they had visited in 2011. Just about 1 in 6 Americans say they think about the events of 9/11 weekly or more often, on par with the 17% who said so in 2011.

The anniversary comes amid a presidential campaign where questions about which candidate would do a better job keeping the US safe have been a central focus. According to results from the same poll released earlier in the week, about 11% of voters name an issue related to terrorism, national security or military policy as their top concern when choosing a presidential candidate, and more voters trust Donald Trump than Hillary Clinton to handle terrorism if elected (51% of registered voters say they trust Trump, 45% Clinton).

Worries about new attacks around the 9/11 anniversary this year are sharper among Republicans than Democrats, and increased worry among Republicans and independents is largely responsible for the shift in overall worry compared with 2011. Now, 65% of Republicans and 50% of independents say attacks are very or somewhat likely around the anniversary, just 36% of Democrats say the same. In 2011, 47% of Republicans, 41% of independents and 33% of Democrats were that worried.

The CNN/ORC poll was conducted by telephone September 1-4 among a random national sample of 1,001 adults. For results among the full sample of adults, the margin of sampling error is plus or minus 3 percentage points.