According to a recent claim from a Border Control union, illegal immigrants are coming into the United States with “active scabies and other illnesses,” while reports have surfaced from a camp in San Antonio of a tuberculosis infection. While common in other areas of the world, these two infections aren’t frequently seen in the U.S.

Scabies are a mite-type parasite that burrow under the skin, leading to itchiness and skin eruptions. Typically they’re found by looking between the fingers, where they often burrow, but they can spread over the entire body.

Symptoms typically begin three to six weeks after infestation, and the disease can be treated with either oral or topical medication to kill the insects. Seven to 14 days after the first dosage, medication must be administered again to ensure the mites are eradicated.

The disease is not very common in the U.S., but has been found in homeless populations.

“It’s usually associated with poor housing, poor socioeconomic status, hygiene issues; think about people living in a crowded place for a long time,” Dr. Olveen Carrasquillo, an associate professor of medicine and chief of division of general internal medicine at the University of Miami’s Miller School of Medicine, told FoxNews.com.

While scabies does spread person-to-person, it’s more common in populations with very close contact.

“Basically it comes down to the chance of exposure to someone who has scabies, where the mite can crawl from one person to another through direct physical contact,” Dr. David Smith of the Center of Infectious Disease Excellence in Flowood, Miss., told FoxNews.com. “Not unless you have really close physical contact with the [infected] person, sleeping in the same bed, living in the same household—it requires really close physical contact.”

According to Smith, there are about 300 million cases of scabies worldwide, but the condition is not highly reported, so there isn’t always reliable data.

Tuberculosis in the U.S.?

Another infectious disease of concern is tuberculosis (TB), which is caused by mycobacterium tuberculosis bacteria. While the bacteria mostly attack the lungs, they can attack any part of the body, including the brain. Active TB is spread person-to person by droplets that an infected person expels when coughing. The droplets go into the lungs and take weeks – or even months – to grow.

Active TB is highly contagious and requires isolation and multi-drug treatments that take between 12 and 24 months to complete. Symptoms include coughing, weight loss, night sweats and blood-streaked mucous. Doctors use chest X-rays, a blood test or a skin test to diagnose the disease.

Like scabies, contact with infected individuals increases a person’s risk for contracting the disease.

“The closer one is, the more time spent in continuity [to an infected person], the more likely you are to get it,” Smith said.

With immigrants coming from high-risk countries, most of them have latent TB, said Carrasquillo, who specializes in minority health.  This occurs when the disease remains in certain lung cavities but is not infectious. It’s typically detected by a chest X-ray and a sputum (mucous) exam. Patients are treated with medication preventatively for six months, in order to reduce the risk of their TB becoming active.

Little is known about how latent TB becomes active TB, Carrasquillo noted, but diagnosing and treating the latent form can prevent activation.

Distinguishing between active and latent TB can be difficult, Smith said.

“It’s one of the most complicated diseases of all time,” he said.