Because warning people about this makes you a racist and a hater of kids

according to President HopeyChangeyPants and friends.  Who don't have to deal with them.
During the recent surge of tens of thousands of young illegal immigrants crossing the Mexico-U.S. border, the Centers for Disease Control warned staff that many will be infected with tuberculosis — but the public wasn't given a head's up.

In fact, the young adults, few of whom had received the types of vaccines U.S. children received, arrived with TB, swine flu and even Dengue, according to reports that eventually filtered out of border agents and hospitals on or near the U.S. border.
...
What's more, the documents obtained in Judicial Watch's investigation of the flood of so-called unaccompanied minors, topping 70,000 a year, revealed that all aren't the little children the administration has portrayed them as. Many are young adults, and gang members.

"The CDC official reveals in the documents obtained by JW as a result of the lawsuit that 'some of these kids are not really kids they are young adults, and we should be wary of personal safety,'" said a memo.
But screw the US public, they don't count.