Haverhill fever (or epidemic arthritic erythema) is a systemic illness caused by the bacterium Streptobacillus moniliformis, an organism common in rats and mice.

[2] The organism S. moniliformis was isolated from the patients and epidemiologically, consumption of milk from one particular dairy was implicated in association with the infection.

The illness resembles a severe influenza, with a moderate fever (38-40 °C, or 101-104 °F), sore throat, chills, myalgia, headache, vomiting, and a diffuse red rash (maculopapular, petechial, or purpuric), located mostly on the hands and feet.

[1] Although the specific form of pathogenesis is still a subject of ongoing research, the bacteria has been observed to result in morphological symptoms that are atypical of bacterial infection.

Autopsy of the victims vividly exhibit erythrophagocytosis, hepatosplenomegaly, interstitial pneumonia, and lymph node sinus hyperplasia.

[4][1] Trypticase soy agar or broth enriched with 20% blood, serum, or ascitic fluid is necessary for the optimal growth of the bacteria under laboratory conditions.

However, S. moniliformis can be biochemically differentiated from similar bacteria by their negative production of indole, catalase, and oxidase, while reduction of nitrate to nitrite.

PCR assay specific for Streptobacillus moniliformis can also be used to detect the bacteria in a patient sample with high accuracy.