Some diseases may not manifest themselves immediately. If travelers become ill after they return home, they should tell their physician where they have traveled.

Most persons who acquire viral, bacterial, or parasitic infections abroad become ill within 6 weeks after returning from international travel. However, some diseases may not manifest themselves immediately, e.g., malaria may not cause symptoms for as long as 6 months to a year after the traveler returns to the United States. It is recommended that a traveler always advise a physician of the countries visited within the 12 months preceding onset of illness. Knowledge of such travel and the possibility the patient may be ill with a disease the physician rarely encounters will help the physician arrive at a correct diagnosis.