We’ve heard it all: Illegal immigrants are criminals. Illegal immigrants steal jobs from Americans. Illegal immigrants refuse to assimilate. Illegal immigrants live off the taxes paid for by Americans.

Regardless of where you stand on these claims, there is another component of the illegal immigration debate that is worth considering as the new administration in Washington prepares to unveil its approach to this contentious issue: the impact of illegal immigration on the health of all who live in the United States (legal and otherwise).

Let’s get to it: dangerous viruses and bacteria are uninterested in an immigrant’s criminal record or employment aspirations. Threatening infectious agents don’t care whether their host body enters America legally via JFK International Airport or slips unnoticed across the Arizona desert in the pre-dawn hours. It’s all the same to our microscopic predators.

This is why for decades and still today, the United States demands that prior to being allowed entrance into our country, those wishing to immigrate must undergo a thorough, well-defined medical history and physical examination performed by a recognized, qualified physician, a medical evaluation that includes blood work and a chest X-ray. According to the Centers for Disease Control and Prevention (CDC), “The purpose of the mandated [pre-immigration] medical examination is to detect inadmissible conditions, including communicable diseases of public health significance, mental disorders associated with harmful behavior, and substance use or .”

Of the many diseases and conditions screened for in immigrant applicants, tuberculosis is likely the best known to the average person. Today, tuberculosis (TB) continues to be a major governmental health focus in immigrants, as the CDC considers TB “one of the world’s deadliest diseases.” Thus, all immigration applicants must be screened for TB via a health history, a physical examination, and a chest X-ray. If any of these arouses suspicion of TB, additional more aggressive screening for the TB bacteria are performed. If TB is identified, the CDC and U.S. Immigration require proof of appropriate TB treatment before the applicant is allowed to enter the United States.

Why all the fuss?

Because of two major realities: (1) according to the World Health Organization (WHO), TB “is one of the top 10 causes of death worldwide,” and (2) tuberculosis is contagious, spread when an infected individual coughs or sneezes tiny bacteria-laden droplets into the air to be inhaled by nearby uninfected individuals. And while life-threatening for those whose immune system is compromised (such as people with HIV and those battling cancer), TB is increasingly dangerous for otherwise healthy individuals, as strains of the TB bacteria resistant to antibiotics are becoming more and more common, leaving physicians and patients with few options to check the progress of the disease once it has entered a healthy body.

In a nutshell, tuberculosis is a bad disease.

So how does this relate to the illegal immigration debate? Because those who enter our country illegally are not screened for TB (or other diseases). And this should be of concern to all of us.

But perhaps this risk is overblown. The question really is: What is the likelihood that those who enter the country illegally pose a real health risk to the American population?

This discussion requires some circumspect analysis, as accurate data on the health of those who cross into the United States illegally (and who try to remain “off the radar”) is hard to come by. So let’s look at some related numbers in our search to answer the question.

Where Do Illegal Immigrants Live in the U.S., and is TB Common in those States?

2010 Pew Research Center estimates rank states with the highest estimated percentage of illegal immigrant residents as Nevada (7.2% of the population), California (6.8%), Texas (6.7%), New Jersey (6.2%), and Arizona (6.0%).

2015 CDC rankings of known tuberculosis cases per 100,000 population list these states as Nevada at #10, California #3, Texas #4, New Jersey #6, and Arizona #13.

Is TB Prevalent in the Most Common Countries of Illegal Immigrant Origin?

It is estimated that in 2014, there were over 11 million illegal immigrants living within the borders of the United States. Mexico remains the country of origin for the majority (52%), with an increasing number now entering illegally from Asia and Central America. The top ten countries of origin for illegal immigrants (2012 data) in descending order are: Mexico, El Salvador, Guatemala, Honduras, Philippines, India, Korea, China, Ecuador, and Viet Nam.

Again, let’s look at TB. There are several potential pitfalls in simply assuming that the incidence of TB in an illegal immigrant population is equivalent to that of the origin country’s general population. Still, knowing how common TB is in a country’s general population at least gives us a ballpark figure. According to 2015 WHO data, the number of people infected with TB per 100,000 in the general population for the top ten illegal immigrant origin countries is:

Mexico – 21

El Salvador – 43

Guatemala – 25

Honduras – 43

Philippines – 322

India – 217

Korea – 80

China – 67

Ecuador – 52

Viet Nam - 137

Let’s start with Mexico, number one in origin of illegal immigrants, but number ten in incidence of TB. If 52% of 11 million individuals illegally emigrated from Mexico, we can (cautiously) estimate that there are over 2,300 infected Mexican illegal immigrants currently living in the United States. What does this mean annually? It is estimated that 720,000 Mexicans attempt to illegally cross into the U.S. annually (roughly half are captured by the U.S. Border Patrol, but based on surveys, many soon attempt to cross the border again). We would calculate that approximately 151 illegal immigrants infected with TB cross into the U.S. annually (half being apprehended, many of whom soon return).

While fewer in number, illegal immigrants from India, China, and the Philippines are many times more likely to be infected with tuberculosis when they silently enter our country.

In the end, no doubt thousands of illegal immigrants currently living across America are actively infected with TB. And hundreds more enter the country annually. For all of these individuals, for their families, for their co-workers, their infection (which often remains undiagnosed for a long period) places their own health and the health of all with whom they interact at serious risk.

And that’s just tuberculosis. Other conditions, such as HIV and syphilis, also pose significant infectious risks to unsuspecting immigrants and those with whom they live, work, and engage.

In the end, it is hard to completely ignore the health risks posed by those whose entry into the country avoids medical examination and treatment. Whether you sit on the “build a wall” end of the spectrum or the “they’re just seeking a better life” end, accepting that treatable major health risks are freely entering into our general population is an unwise strategy, regardless of your political leaning (assuming those risks are meaningful, a debate we can have).

Whether or not health risks will factor into the new Trump administration immigration policy remains to be seen. But they certainly should.