The incidence of communicable diseases is such that they are unlikely to prove a hazard for international travelers greater than that found in their own country. There are, of course, health risks, but in general, the precautions required are minimal.

Certain diseases occasionally occur, such as plague, rabies in wildlife, including bats, Rocky Mountain spotted fever, tularemia, arthropod-borne encephalitis, and seasonal outbreaks of influenza. The comprehensive CDC Influenza site answers questions raised about this 2003-2004 influenza season.

Rodent-borne hantavirus pulmonary syndrome has been identified, predominantly in the western states of the United States. Lyme disease is endemic in the northeastern United States, Mid-Atlantic, and the upper Midwest and the southwestern provinces of Canada. Occasional cases have been reported from the Pacific Northwest. Recently, cases of West Nile virus have occurred throughout North America. During recent years, the incidence of certain foodborne diseases, e.g., E. coli O157:H7 and salmonellosis, has increased in some regions. Other hazards include poisonous snakes (please see Animal-Associated Hazards), poison ivy, and poison oak. In the north, a serious hazard is the very low temperature in the winter.

In the United States, proof of immunization against diphtheria, measles, poliomyelitis, and rubella is now universally required for entry into school. In addition, the school entry requirements of most states include immunization against tetanus (49 states), pertussis (44 states), mumps (46 states), and hepatitis B (26 states). Haemophilus influenzae type b (Hib) vaccine is not required for school entry but is required in 49 states for attendance in day care facilities.

Isolated cases of bovine spongiform encephalopathy (BSE/mad cow disease) have been reported in Canada and the United States. For more information, see http://www.cdc.gov/ncidod/diseases/cjd/cjd.htm and http://www.usda.gov.

Canada
For health information on traveling in Canada, please see Canada's Laboratory Center for Disease Control, which includes updates on current Canadian outbreaks.