COMMUNICABLE DISEASE-CHALLENGE FROM ABROAD.
D001359:Aviation; D003140:Communicable Disease Control; D004813:Epidemiology; D006801:Humans; D012899:Smallpox; D014195:Travel; D014481:United States; D014611:Vaccination
AVIATION; COMMUNICABLE DISEASE CONTROL; EPIDEMIOLOGY; SMALLPOX; TRAVEL; UNITED STATES; VACCINATION