SALMON, Idaho Nearly a dozen people in Washington state and Montana who had contact with infected goats have been diagnosed with Q fever, a disease common among livestock but rare in humans, state and federal health officials said on Thursday.
The ailment, which can cause fevers and other flu-like symptoms, is the confirmed or suspected cause of illnesses reported in six people in Montana and five more in Washington, where the outbreak began in May.
By comparison, Washington typically averages three human cases of Q fever per year, said state Department of Health spokesman Donn Moyer.
"We're certainly looking at more people than usual," he told Reuters.
Q fever, which is treated with antibiotics, can pose a severe risk to people with heart-valve defects or compromised immune systems. It also can cause pregnant women to miscarry, health experts said.
Health and agriculture investigators in Washington have traced the outbreak to a goat herd in the central part of the state where animals on two farms have since been quarantined.
The goats from one of the farms were sold to at least one livestock operator in Montana, where three human cases are confirmed and three more suspected, officials said.
Jason Kelly, spokesman for the Washington Department of Agriculture, said animals from the infected herd also were sold in nine other counties in Washington, bringing to 10 the number of counties where local health agencies are on alert for the disease and where livestock inspectors are testing goats.
Q fever usually spreads into the environment through an infected animal's birthing materials.
The disease can cause pregnant goats, sheep and cattle to abort their young but more often goes undetected because animals exhibit no symptoms.
Alicia Anderson, senior veterinary medical officer with the federal Centers for Disease Control and Prevention, said a probe of the outbreak suggests bacteria were inhaled by people in areas where barnyard dust was tainted with birthing material and feces from infected goats.
Anderson said it is rare for people to transmit the disease, which is underreported and often undiagnosed because many of the infected show no symptoms.
She said the rise in infections in the two states triggered requests earlier this month for the CDC to aid in the investigation. Other routes of human infection include unpasteurized milk and tick bites.