User:Jennifer Old/sandbox

Despite there being multiple strains of ehrlichiosis, there are only two strains, Ehrlichia chaffeensis and Ehrlichia ewingii, that are currently known to cause the disease in humans.

Amblyomma americanum ticks spread the E. chaffeensis and E. ewingii strains of the Ehrlichiosis bacterial infection in the Eastern and Southeastern areas of the United States, while A. phagocytophilum is spread by the Ixodes scapularis tick in the Upper Midwest. 1,518 cases of E. chaffeensis were recorded in southeastern, south-central and mid-Atlantic areas of the country in 2013. Despite the first cases of "E. ewingii" appearing in the Missouri in the year 1999, this strain was not reportable to health officials until 2008. Since 2008, there have been reported human cases of E. ewingii in Oklahoma, Arkansas and Tennessee though it is observed less frequently than E. chaffeensis.

During 2008-2012, 4,613 cases of E. chaffeensis infections were reported through the National Notifiable Diseases Surveillance System (NNDSS). The incidence rate (IR) was 3.2 cases per million person-years (PYs). The hospitalization rate (HR) was 57% and the case fatality rate (CFR) was 1%. During that same time period, 55 cases of E. ewingii infections were reported through NNDSS. The national IR was 0.04 cases per million PY. The HR was 77% and the case fatality rate was 0%.

In Minnesota and Wisconsin four people reported symptoms that are associated with Ehrlichiosis, and upon further research it was discovered that neither of these cases were E. chaffeensis or E.ewingii, but instead it revealed a new species similar in genetic makeup to the E. muris strain. Ixodes Scapularis ticks are hypothesized to be the transmitting vector of the E. muris strain in these states.