An outbreak of Q fever, carried by domestic goats, infected about 20 people in Montana and Washington state last spring, the federal Centers for Disease Control reported in its October 14 Morbidity and Mortality Weekly Report.

Four people were hospitalized, but no deaths were reported, and some of the infected people showed no symptoms.

The outbreak became known in April, when the Q fever bacterium Coxiella burnetii was detected in a goat placenta collected from a Washington farm that had reported a high rate of aborted goat pregnancies.

Goats from the farm had been sold across the region, and health officials eventually detected C. burnetii in goats at 21 farms, most of them in Washington and Montana.

Q fever cases are reported every year, including about three cases per year in the Pacific Northwest, the CDC said.  C. burnetii is considered highly infectious, is persistent in the environment and can travel many miles when windborne.

Cattle, sheep and goats are the primary carriers, and the organisms are excreted in milk, urine and feces of infected animals. Human-to-human transmission is rare.

Humans, especially pregnant women and people with compromised immune systems, are often very susceptible to the disease, and it takes only a very few organisms to cause infection, according to the CDC.

To prevent Q fever outbreaks, the CDC recommends, among other precautions, appropriate disposal of sheep and goats’ placenta, consuming only pasteurized milk and milk products, and restricting access to barns that are used to house potentially infected animals.