Valley Fever Maps

This map shows the approximate areas in the United States and Mexico where we know or suspect the fungus that causes Valley fever lives. These are considered endemic areas for Coccidioides, the fungus that causes Valley fever.^1–6 Much of what is known about where the fungus lives in the southwestern United States is based on skin testing studies performed in the late 1940s and early 1950s.² The map also shows the locations of several outbreaks and locations of Valley fever cases acquired outside of the areas identified by those studies. Coccidioides might also live in similar areas with hot, dry climates that are not shaded on the map.

Most cases of Valley fever are not part of an outbreak. However, Valley fever outbreaks linked to a common source do occasionally occur, particularly after events that disturb large amounts of soil. This map shows the locations of 40 Valley fever outbreaks that happened during 1940–2015.⁷ Some of these outbreaks happened in places where scientists did not expect the fungus to live. Investigating Valley fever outbreaks helps public health officials understand:

• Where the fungus lives,
• Activities that may make someone more likely to get Valley fever, and
• Groups of people more likely to get Valley fever

In certain states, health departments collect information about cases of Valley fever and then send the information to CDC through the National Notifiable Diseases Surveillance System (NNDSS). This map shows the average incidence of reported Valley fever per 100,000 people, by county, during 2010–2015. The rates in counties with fewer than five reported Valley fever cases, indicated by cross-hatching, might not be reliable. On this map, cases of Valley fever are classified according to people’s county of residence, which may not be where they acquired the infection. Cases in areas outside of regions where the fungus Coccidioides is believed to live are likely associated with travel to those disease-endemic areas.