Protestors camping out in groups like Occupy Wall Street aren’t just at risk of getting arrested, rained on, or frozen in a makeshift tent. They’re also at risk from germs and other factors that can cause serious illnesses.

In New York, hundreds of activists are packed together day and night in Zuccotti Park, where cigarettes are shared and nobody’s getting much sleep. Already, a lot of activists have what’s called “Zuccotti lung,” a hacking cough that seems to be spreading from person to person.

Germ expert Dr. Philip Tierno says that people crowded together in tent camps are also at high risk for respiratory viruses, like tuberculosis and Norovirus, which causes vomiting and diarrhea and could quickly overwhelm the camp’s limited bathroom facilities. In fact, sanitation is a huge problem with protestors tossing food on the ground to rot and urinating in bottles instead of waiting in line for the bathroom. Protestors are also living in damp clothing and carrying rain-soaked signs, which are perfect for growing mold.

Dr. Tierno compares Occupy Wall Street conditions to pilgrimages in Mecca, where huge groups of campers have come down with respiratory infections and diseases connected to contaminated water, like cholera.

Activists who get sick aren’t necessarily going home because they believe getting sick is a badge of honor and just one of the many sacrifices they have to make for a successful protest.

Even worse, the illnesses may not be contained in the camp for long, because Occupy Wall Street protestors have made it a mission to shake the hand of everyone who passes by.