The writer is a pediatrician in Washington and a board member of the National Physicians Alliance.

People across not just the United States but also the world were horrified on Dec. 14, when 20 children and six staff members at Sandy Hook Elementary School were murdered by a gunman with an assault rifle. Yet in the six months since the tragedy in Newtown, Conn., 362 children and teens and 4,614 adults have died in the United States from gun violence — and nothing has been done on the national level.

Much has been said — particularly by leaders of the National Rifle Association — about gun control as an issue of rights. The rights issue has been settled: Americans have a Second Amendment right to own guns. But because of the societal and economic impact of gun violence, this is an issue of not just gun rights but also health, justice and economic development.

The data tell a horrible tale: In the United States in recent years, firearm homicide was the second-leading cause of death (after motor vehicle crashes) for those ages 1 to 19. Gun violence is declining but still striking: According to a Bureau of Justice Statistics report last month, firearm-related homicides fell from 11,101 in 2011 to 18,253 in 1993. And this is the good news?

Nor is this just an urban issue: Gun violence cost the United States $174 billion in 2010, according to the Pacific Institute for Research and Evaluation, which assessed medical bills, lost productivity, insurance and more.

Action at the state level is not enough. Sensible federal legislation is necessary. Polling for the group Mayors Against Illegal Guns found that “82 percent of gun owners — including 74 percent of National Rifle Association members — support requiring criminal background checks for anyone purchasing a gun.” Washington Post-ABC News polling in December found that 54 percent of Americans favor stricter gun laws, with 59 percent supporting a ban on high-capacity magazines.

Thirty-three people in this country are killed by guns every day, Mayors Against Illegal Guns noted in February. Our society must make changes. As we remember the victims of the Newtown shootings, let us take action to prevent such an atrocity from ever happening again.