Ehrlichiosis and Anaplasmosis are two distinct but related bacterial infections primarily transmitted to humans by tick bites. Both diseases can cause flu-like symptoms and are most common in areas where their specific tick vectors reside across the United States. Ehrlichiosis is caused by Ehrlichia species, and Anaplasmosis by Anaplasma phagocytophilum.
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Human Anaplasmosis (initially called Human Granulocytic Ehrlichiosis) was first recognized in the United States in the early 1990s, while Human Monocytic Ehrlichiosis caused by *Ehrlichia chaffeensis* was identified in the mid-1980s. Their emergence highlighted the increasing public health threat posed by newly recognized tick-borne diseases, leading to significant research efforts.
Both diseases are transmitted through the bite of infected ticks. Anaplasmosis is primarily spread by the **blacklegged tick** (*Ixodes scapularis*) in the Northeast and Upper Midwest US, and the **western blacklegged tick** (*Ixodes pacificus*) in the West. Ehrlichiosis (specifically *E. chaffeensis*) is mainly transmitted by the **lone star tick** (*Amblyomma americanum*) across the South-Central, Southeastern, and Eastern US.
Contagious Period: Varies by disease
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Our AI-powered surveillance hasn't detected significant Ehrlichiosis and Anaplasmosis activity in the past 30 days.
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Currently, Ehrlichiosis and Anaplasmosis case counts are within baseline expectations globally. However, diseases can emerge rapidly, which is why continuous monitoring is critical.
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Even without active outbreaks, understanding Ehrlichiosis and Anaplasmosis prevention helps protect you and your community:
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Trusted information from leading health organizations
Official guidance from the U.S. Centers for Disease Control and Prevention
View CDC Resources →Global disease surveillance and guidelines from the World Health Organization
View WHO Resources →Disease information on Virus Watcher is reviewed by our Chief Epidemiologist, a former CDC lead analyst for FluSight forecasting. Outbreak data is aggregated from verified sources including BEACON, ProMED, WHO, CDC, and 50+ national health agencies. This information is for educational purposes and should not replace professional medical advice.
Last reviewed: 2026-07-19
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