The preventive measures you need to take while traveling in East Asia depend on the areas you visit and the length of time you stay. You should observe the precautions listed in this document in most areas of this region. However, in highly developed areas of Japan, Hong Kong, South Korea, and Taiwan , you should observe health precautions similar to those that would apply while traveling in the United States. Travelers' diarrhea , the number one illness in travelers, can be caused by viruses, bacteria, or parasites, which can contaminate food or water. Make sure your food and drinking water are safe.
Malaria is a preventable infection that can be fatal if left untreated.
For additional information on malaria risk and prevention, see Malaria Information for Travelers to East Asia . A certificate of yellow fever vaccination may be required to enter certain of these countries if you are coming from tropical South America or sub-Saharan Africa. For detailed information, see Comprehensive Yellow Fever Vaccination Requirements . Dengue , filariasis , Japanese encephalitis , leishmaniasis , and plague are diseases carried by insects that also occur in this region. If you visit the Himalayan Mountains, ascend gradually to allow time for your body to adjust to the high altitude, which can cause insomnia, headaches, nausea, and altitude sickness.