It's unclear why the mites are here
The cause of the region's mite bite outbreak has experts scratching their heads.
And their arms.
And their necks.
And their torsos.
Entomologists and health officials cannot explain why the pesky mites -- largely believed to be itch mites -- have inundated the Chicago area. Though outbreaks have been documented in Kansas, Nebraska and Missouri in recent years, this is the first time they've sunk their teeth into northern Illinois.
"It may have to do with the weather or other environmental conditions," said Linda Murray, chief medical officer for the Cook County Department of Public Health. "We don't know why."
Whatever the reason for their arrival, the mites are making their presence felt. Health officials say more than 500 people have been treated for rashes at suburban Cook County hospitals in the past two weeks -- more than double the typical number.
In DuPage County, several dozen people have visited local emergency departments complaining of red, quarter-sized, circular lesions on their skin. County health officials say they have received about 100 phone calls from concerned residents.
The bites are annoying and uncomfortable, but they do not pose a serious health risk, experts said. The symptoms, which can last up to 14 days, can be treated with calamine lotion and over-the-counter antihistamines, health officials said.
"It's mostly a rash and itching like a mosquito bite," Murray said. "There's no comparison in terms of human health to the West Nile virus."
If more serious symptoms such as headaches or high fevers persist, Murray advises people to seek medical attention. In typical cases, she says, professional care isn't necessary.
"Give your doctor a call if you're worried," she said, "but personally I wouldn't go to the emergency room and sit there for four hours."
As local health officials tried to reassure the public Tuesday, state experts left traps out for a second night in hopes of identifying the bugs behind the bites. Monday evening's heavy rains hampered the first collection attempt.
"We do know it's mites," said Kitty Loewy, spokeswoman for the Cook County public health department. "We're going to go out on a limb here and assume it's itch mites."
Local experts base their assumptions upon a similar outbreak in Nebraska three years ago. In fall 2004, hundreds of residents in the southeastern part of the state reported coin-sized welts on their necks, shoulders and upper torsos.
The outbreak caused a public health scare until researchers at Kansas State University and University of Nebraska determined the relatively innocuous itch mite was the culprit. Itch mites -- or Pyemotes as they're known in entomology circles -- make their homes in red or pin oak trees.
The microscopic creatures nestle in the trees' galls, the thickening margin usually found in the notches of leaves. The mites often drop to the ground in search of nutrients during the evening hours, said Jim Kalisch, an entomologist at the University of Nebraska.
"The mites reproduce so rapidly, their food source dwindles and they have to look outside the trees," Kalisch said.
As the mites fall from the branches, they can drop on people walking beneath the limbs. The tiny creatures slip through loose collars and land on exposed skin areas such as shoulders, necks and upper torsos.
The pests usually hang around until the first hard frost of the season, Kalisch said. During a mild Nebraska fall two years ago, however, they kept biting until December.
"Year after year," Kalisch says, "the weather takes care of the mites."