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.
Reference:
CDC Health Information for International Travel

