Dr Meeta Khan, wears a face mask as she examines a respiratory patient at the Rush University Hospital emergency department. (Charles Rex Arbogast/AP)

The writer is the scientific director of the International Union Against Tuberculosis and Lung Disease.

John Armstrong, Florida’s top health official , sent a letter last month to the heads of the Department of Health and Human Services and the Federal Emergency Management Agency — taking the extra step of copying the media — requesting that they tell him how many of the children who recently crossed the U.S. border from Mexico are in Florida and what illnesses they have. In asserting that this information was “urgently needed and is vital to guarding the health and safety of Florida communities, ” Armstrong fanned anxieties that the influx of children from Central and South America poses a large-scale threat to public health.

Likewise, Georgia Rep. Phil Gingrey, a chair of the GOP Doctors Caucus, penned a letter last month to Centers for Disease Control and Prevention Director Tom Frieden requesting a national threat assessment, claiming he had heard reports of children crossing the border “carrying deadly diseases such as swine flu, dengue fever, Ebola virus, and tuberculosis.” The congressman later added smallpox to his list of diseases of concern.

Let’s everybody calm down. No one has ever been infected with Ebola in the Western Hemisphere, dengue fever isn’t transmitted from human to human, only one confirmed case of flu has been found so far among the children and smallpox has been eradicated worldwide.

That leaves tuberculosis, an infectious disease that actually is of great public health concern. TB is an airborne illness, caused by a bacterium that can infect any part of the body, though it typically affects the lungs. Symptoms include severe weight loss, lethargy and bloody coughing. It can be fatal without treatment.

I certainly share the concern that the American public is not adequately protected from TB. But as a doctor who led the response to an actual TB epidemic in New York City in the 1990s, I feel compelled to explain that tuberculosis already exists in the United States. It has always been here. By far the most effective way of protecting Americans from it is to provide the public health system with the resources it needs to treat and prevent the disease in our communities every day.

The United States faced a TB epidemic in the 1980s and 1990s that was the direct result of years of gutted federal and local funding for basic control activities. Ultimately, it cost a billion dollars to stop the spread of the disease just in New York — far more than it would have cost if we had simply maintained the basic infrastructure needed to diagnose and treat those infected.

As a recent article in the New England Journal of Medicine laid out, health officials working to control TB today are facing funding challenges similar to what we faced then. According to the report, municipal funding for TB control has been cut by more than half since the 1990s, and federal spending on anti-TB efforts has dropped 15 percent. In fact, in 2012, Armstrong himself oversaw the closing of Florida’s A.G. Holley Hospital — one of the nation’s leading TB treatment facilities.

Such neglect has already led to serious shortages of TB medications and diagnostics. Notably, since 2005, there have been major disruptions in the supply of the TB drug isoniazid, as well as tuberculin, which is used to diagnose TB infection.

As a result, there is a rash of new TB cases in this country, mostly in large urban settings, where population densities are conducive to transmission. Most recently, a Sacramento school experienced an outbreak in which 120 students and employees have been found to be infected since February.

If U.S. leaders are concerned that tuberculosis poses a threat to public health, they’re right. But that threat doesn’t stem from the recent influx of undocumented children. It has arisen from years of neglect of our core institutions tasked with preventing and treating TB.