If you are an American man, you will probably die at least two years and two months earlier than men in other high-income countries. Men in Australia and Iceland live into their 80s. American men, on average, die at 76.

What kills them sooner? It's not heart disease or cancer. It's mostly a combination of three things. We can talk about two of those things, car crashes and drug overdoses, but it's difficult to have a discussion about the third and biggest contributor to the shortened lives of American men. Guns.

Gun violence cuts more than five months off the life expectancy of American men, say researchers at the National Center for Health Statistics who compared the life expectancy of men in a dozen high-income countries.

If the biggest contributor to the life expectancy gap were cancer, we would have screening programs, education campaigns and treatments developed to halt it. But out of fear of offending Second Amendment rights advocates, we refuse to talk about gun violence as a public health threat, and that silence is killing thousands.

Some cities are starting to treat gun violence like an illness. When a Delaware city experienced a 45 percent increase in shootings over two years, local officials called in disease detectives from the Centers for Disease Control and Prevention.

Those investigators are usually tasked with studying and stopping epidemics of diseases such as meningitis and HIV or limiting the health effects of a natural disaster. But in Wilmington, Delaware, they used the same tools they employ to curb infections to understand why gun violence was on the rise. Their worked help city officials understand who is most at risk of becoming a victim of gun violence and when to intervene to prevent shooting deaths.

You might think the CDC is banned from studying gun violence. It is true that in 1996 a Congressional bill cut $2.6 million from the CDC budget, the exact amount the agency spent on gun research the previous year. An amendment added to a Congressional bill that same year said "None of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control."

Since the not-quite-a-ban amendment, the CDC has been fearful of studying gun violence. Critics say the CDC investigation of the gun violence epidemic in Delaware skirted the real issues with disease detectives fearful to study how people acquired guns and investigate if policies to limit access to guns would slow the epidemic.

The interjection of gun politics in health is nowhere more apparent than in Florida. Second Amendment activists there supported a 2011 law that makes it illegal for a doctor to "ask questions concerning the ownership of a firearm" during a consultation.

The purpose of the law, they say, is to protect patient privacy. Except existing laws already protect patient privacy. What the Firearm Owner's Privacy Act does is stop doctors from asking about gun ownership and ban pediatricians from asking parents how guns are stored in the home.

A doctor charged with making sure kids are safe can lose his or her license for asking if parents own a gun safe and know how to store guns safely. (Close to 1.7 million American children live in homes where guns are stored loaded or are not locked away, according to the Law Center to Prevent Gun Violence.)

When a Florida judge issued an injunction against the Florida law in 2012, the court of appeals reversed it saying, "The practice of good medicine does not require interrogation about irrelevant, private matters."

Guns are a relevant, public health threat and good medicine requires honest discussions about everything from eating habits to gun ownership. By talking about deaths from driving, we've made strides in road safety through seat belts and speed limits. We could make gun ownership safer for everyone. But it's hard to treat an illness if you refuse to talk about it.

Seema Yasmin is a staff writer at the Dallas Morning News and a professor of public health at the University of Texas at Dallas. She is a physician and former disease detective at the Centers for Disease Control and Prevention. Twitter: @DoctorYasmin