Gun violence killed more than 2,500 people in 2018 in Tijuana, the Mexican city of 1.8 million residents. That year, in San Diego, 21 miles away, with 1.4 million people, the number was 86.

Why the big difference?

The usual explanations range from Mexicans being prone to violence to drug cartels, whereas Americans are more peaceful. But there may be another explanation.

Journalist Jack Herrera visited both cities and reported in The Nation on May 18: “For researchers studying violence, trying to understand why a city like Tijuana has become violent can look similar to trying to understand why the people of Flint, Michigan, began feeling sick in 2014 … It feels like the arrival of a plague, some disease that can spread through a neighborhood and take lives.”

Charlie Ransford, director of science and policy for Chicago-based Cure Violence, agreed, telling Herrera, “The No. 1 predictor of whether a person will go on to commit violence, more than anything else, is if that person has been exposed to violence in the past.”

In Cure Violence’s first year working in a deadly Chicago neighborhood, Herrera said, gun deaths dropped by more than 67 percent, a success replicated in 20 American cities and countries such as Salvador, Honduras, Syria, Iraq. In fact, he added, in the coronavirus era, Cure Violence retrained its staff “to encourage public health practices that discourage the spread of both the virus and violence.”

There is another epidemic, which is ravaging rural America. The Centers for Disease Control and Prevention (CDC) reported that, in 2018, opioids killed 46,802 people. More than 100 billion doses of oxycodone and hydrocodone, The Washington Post reported, were manufactured and distributed between 2006 and 2014.

Like the virus, what opioid overdose and gun violence have in common is that they can be “treated.” The Post reported on Nov. 5, last year, that four companies accused of making or distributing the deadly painkillers agreed to a $26 billion settlement in a lawsuit filed by numerous counties and cities. “While no dollar figure can restore the lives and families already devastated by the crisis, these settlement dollars are desperately needed in areas that have been hardest hit by this man-made epidemic, particularly as they now grapple with covid-19,” the attorneys said.

Not so for firearms. The National Rifle Association (NRA) pushed Congress to pass the Protection of Lawful Commerce in Arms Act in 2005 giving the firearms industry immunity from most lawsuits.

A decade earlier, the late Arkansas Republican Sen. Jay Dickey forced into the 1996 federal government’s omnibus spending bill banning the CDC from using funds to study the causes of gun violence, fearing the findings could “be used to advocate or promote gun control.” Democrat Bill Clinton signed the bill and it remained intact through the presidencies of Republican George W. Bush, Democrat Barack Obama and Republican Donald Trump.

Following the massacre at a movie theater in Aurora, Colo., in July 2012, Dickey relented. He joined Mark Rosenberg, director of the CDC’s National Center for Injury Prevention to pen a mea culpa in The Post on July 27, 2012. They noted that the CDC’s investigation of the causes of automobile fatalities have led to measures which have “markedly reduced traffic deaths.” They added that “scientific research should be conducted into preventing firearms injuries … and ways to prevent firearms deaths.”

It is important to pay attention to who are the victims of gun violence. As this column has reported previously, two-thirds of the deaths are due to suicide; 20 percent of the victims are men aged 15 to 34 probably shot by other males; and around 1,700 are women, probably killed by domestic violence. But, of the 300 million to 400 million guns in private hands, including between five million and 30 million assault rifles, only three percent of Americans own half of them, The Guardian reported. So there is not necessarily a correlation between the number of firearms and gun deaths.

CDC studies of the underlying causes could do for the firearms industry what the agency’s research has done for the automobile industry: provide science-based data on which to develop policies to minimize the fatalities.

And, as in the case of the coronavirus, some Americans would stand to benefit greatly. “Many of the same Black and Latino neighborhoods in cities across the nation have been disproportionately affected by both epidemics,” USA Today’s Grace Hauck reported last month.

Congress finally approved funds for research by the CDC into gun fatalities, Nidhi Subharaman reported in Nature on Dec. 17, 2019. But, for the 20 years of the ban, “We lost several generations of researchers in this field and it’s going to take a while to build that back up,” said David Studdert, a health law expert at Stanford Law School told Subharaman.

That – and the tens of thousands of lives lost to gun violence while heartless elected officials played politics with the CDC.