The U.S. Department of Health and Human Services and the Centers for Disease Control and Prevention require that all legal immigrants receive a medical exam. Proof of vaccination is also mandatory for measles, mumps, rubella, polio, tetanus, diphtheria, pertussis, haemophilus strains, hepatitis A and B, rotavirus, meningococcus, chicken pox, pneumonia, and seasonal flu.
None of these rigorous screenings can be done in advance of entry on people who enter this country illegally and undetected. And once people are detained, the screenings they receive are not nearly as rigorous or effective at controlling the spread of disease. This is the reason that we have a potential public health crisis along our southern border.
As many as 50,000 children, mostly from Central American countries, are now being housed in cramped makeshift detention centers by the U.S. government. Unfortunately, they are not being detained for the purpose of identifying illness, with Immigration and Customs Enforcement relying on self-report of symptoms, and many have already been sent to other states, where disease can spread.