How to get sick on the U.S. campaign trail- Little sleep, bad food, germs everywhere

U.S. Democratic presidential candidate Hillary Clinton coughs onstage during a campaign stop at the 11th Congressional District Labor Day Parade and Festival in Cleveland, Ohio, United States September 5, 2016. REUTERS/Brian Snyder

WASHINGTON (Reuters) - Hillary Clinton's bout of pneumonia has shed light on a problem seldom seen by American voters: The long days, little sleep, cross-country travel, bad food and kissing babies add up to a recipe for illness for presidential candidates and aides.

Avoiding viruses and other ailments can be next to impossible for people who spend months in the close confines of campaign planes and buses.