FIGHTING CONTAGION

Pathogens Like to Travel

Pathogens — more popularly known as "germs" — spread, finding appropriate accommodations in which to settle and multiply. Some travel by air. Some travel by water or in liquids and foods. And many attach themselves to clothing and various surfaces — posing an ever-present threat to humans. Pathogens may also be spread by single or multiple vectors — animals such as rats, fleas, ticks, or mosquitoes that carry the germs or pathogens internally. The warm, moist surfaces of human hands provide an accommodating place for germs to linger and multiply.

The 1918 Influenza: The Deadly Spread of a Mysterious Disease

In 1918, an unidentified killer disease — later identified as a particularly virulent form of influenza — appeared and rapidly became pandemic, reducing the world's population by 20 to 50 million people by the time it ran its course. Scientists now know that this mysterious disease was caused by a well-traveled virus too small to be seen with microscopes of the time. The close quarters of recruits in American military camps and the large-scale movement of troops between and within the United States and Europe during World War I certainly helped spread the disease. Influenza quickly became the single most deadly American epidemic of the 20th century. People knew it was contagious, and suspected that it was airborne, but were incapable of stopping it — despite gauze masks worn for that purpose.

Left: Customer turned away from a San Francisco trolley for lack of a mask, as required by an emergency city ordinance, 1918.

Upper Right: Dressed for work, 1918.

Lower Right: American soldiers with gauze masks, during World War I, 1918.