Under current law, foreign nationals not already legally residing in the United States who wish to come to the United States generally must obtain a visa and submit to an inspection to be admitted. They must first meet a set of criteria specified in the Immigration and Nationality Act (INA) that determine whether they are eligible for admission. Moreover, they must also not be deemed inadmissible according to specified grounds in the INA. One of the reasons why a foreign national might be deemed inadmissible is on health-related grounds. The diseases that trigger inadmissibility in the INA are those communicable diseases of public health significance as determined by the Secretary of Health and Human Services (HHS).
Currently there are seven diseases deemed communicable disease of public health significance: chancroid, gonorrhea, granuloma inguinale, infectious leprosy, lymphogranuloma venereum, active tuberculosis and infectious syphilis. Other diseases incorporated by reference are cholera; diphtheria; infectious tuberculosis; plague; smallpox; yellow fever; viral hemorrhagic fevers (Lassa, Marburg, Ebola, Crimean-Congo, South American, and others not yet isolated or named); severe acute respiratory syndrome (SARS); and "[i]nfluenza caused by novel or reemergent influenza viruses that are causing, or have the potential to cause, a pandemic." The INA also renders inadmissible foreign nationals who are not vaccinated against vaccine-preventable diseases. Vaccinations are statutorily required for mumps, measles, rubella, polio, tetanus, diphtheria, pertussis, influenza type B and hepatitis B. Vaccinations against other diseases may also be required if recommended by the Advisory Committee for Immunization Practices (ACIP).