Upon arrival at Ellis Island, immigrants were ushered into a room called the Great Hall and paraded before a series of medical officers for physical inspection. Most were allowed to pass by in a matter of seconds, but those whom the doctors deemed physically or mentally deficient were marked with chalk and taken away for additional screening.
Questionable candidates were forced to submit to more detailed questioning and medical exams, and any signs of contagious disease, poor physique, feeblemindedness or insanity could see an immigrant denied admittance on the grounds that they were likely to become a ward of the state.
In later years, doctors at Ellis Island even devised puzzles and memory tests to ensure that certain immigrants were intelligent enough to find work.
New arrivals could also face rejection if they were anarchists, had a criminal record or showed signs of low moral character.
Despite the litany of guidelines for new immigrants, the number of people denied entry at Ellis Island was quite low. Of the 12 million people who passed through its doors between 1892 and 1954, only around 2 percent were deemed unfit to become citizens of the United States.
https://www.history.com/news/9-things-you-may-not-know-about-ellis-island
"CDC stats from 2017 show that 70% of reported cases of TB in the United States
was found among non-U.S.-born individuals.
Migrants from Mexico accounted for the largest share."
Especially read post # 21, which describes the little known history,
as well as the evaluation purpose of Ellis Island as an immigrant reception center.