West Nile virus, valley fever, hantavirus: Over the past decade, the West has seen an increase in some rare but scary illnesses. According to a September study in the American Journal of Tropical Medicine and Hygiene, the U.S. places 11th globally for incidents of plague. Scientists also recently discovered that a deadly tropical fungus, which first appeared in the Pacific Northwest roughly a decade ago, has moved further into the U.S.
Worldwide, many tropical and subtropical diseases are spreading, thanks to climate change, biodiversity loss and easy global travel. Pathogen-carrying pests like mosquitoes thrive in warmer, wetter conditions, while biodiversity declines give diseases easier access to their preferred hosts.
Scientists know little about some of the West's nastiest diseases -- except that they are becoming more common. Some are easily dodged (avoid mouse droppings that might carry hantavirus); others are more insidious (lung fungus spreads easily through the air). Here are more facts about some strange -- and alarming -- Western diseases.