Subscribe Now! National Geographic Magazine $15
Visit our Online Shops

Sign up for free


Once a month
get new photos
and expert tips.

Mexicali and Calexico

Photo: Aerial view of Mexicali and Calexico
Heavily traveled international borders, like the one seen here between Mexicali, Mexico, (right) and Calexico, California, (left) can present acute public health concerns. Migrants from Mexico, where health care is often poor and vaccination rates low, can carry diseases that have been nearly eradicated in the United States. Likewise, U.S. travelers can introduce new diseases to rural Mexico, where they can spread quickly. The smallpox virus changed much of Mexican history when, in the early 1500s, Spanish conquistadors brought the disease to the New World. A subsequent epidemic wiped out much of the local population, bringing on the collapse of the Aztec Empire.
Photograph by Karen Kasmauski

Health and Human Body Topics


Photo: 2009 Winner

Photo Contest

Find out who takes home the Grand Prize!

Photo: Man carrying a kayak

Adventure Videos

Check out adventure videos from our West Coast Adventure Editor Steve Casimiro and go "Behind the Lens."

The Green Guide

Photo: Green flower

Get tips for helping the environment.

Support Conservation

Photo: Two penguins

Help conserve the world's natural resources.