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An eight-year-old Wright County child tested positive for the illness in a commercial laboratory, and further confirmatory testing is being done by MDH. The child was hospitalized but has been released and is recovering.

LaCrosse virus is transmitted through the bite of infected Eastern treehold mosquitoes, which feed primarily during the day. Every summer, MDH officials routinely recommend a number of preventive measures for people who live in parts of the state where the LaCrosse virus is commonly found. Those recommendations include:

• Use mosquito repellent containing no more than 30 percent of the active ingredient DEET when in wooded areas frequented by the tree hole mosquito.

• Wear long-sleeve shirts and long pants if you have to spend time in an area where mosquitoes are biting.

• Eliminate possible mosquito-breeding sites on and around property - including items such as old tires, buckets, clogged rain gutters, bird baths, cans and other containers and anything else that can hold a small amount of water.

Health officials are urging Minnesota residents to take similar measures to protect themselves form the mosquito-borne West Nile virus. The year's first human case of West Nile was reported July 17.

"The appearance of the first LaCrosse encephalitis case within days of the first West Nile virus case underscores the fact that both mosquito-borne illnesses will now be a part of life in Minnesota the rest of the summer," said Dr. harry Hull, state epidemiologist. "Everyone needs to be vigilant about preventing mosquito bites."

LaCrosse has been a fixture of life in th upper Midwest for many years, according to David Neitzel, an epidemiologist with MDH specializing in diseases spread by mosquitoes and ticks.

Like all forms of encephalitis - including West Nile - LaCrosse encephalitis affects the brain and central nervous system. Severe cases of LaCrosse - which occur primarily in children and adolescents under the age of 16 - are characterized by symptoms like high fever, headache, confusion and other neurologic symptoms. Approximately 15 percent of patients with LaCrosse encephalitis experience long-term neurologic problems.

Most infections of LaCrosse - like most infections of West Nile - tend to be mild, and many people experience no symptoms at all. However, severe cases of West Nile tend to occur in older people, rather than children or adolescents.

Since 1985, 114 cases of LaCrosse (including one death) have been reported to MDH. Thirteen cases were reported last year. About half of the reported cases occurred in children six years of age or younger. Almost all of the cases occurred in a relatively small area of the state, stretching from just west of Lake Minnetonka in the Twin Cities through the hardwood forests of southeastern Minnesota, along the Mississippi River.

The "high risk" areas for LaCrosse activity in Minnesota include portions of 19 different counties, including Anoka, Blue Earth, Carver, Dakota, Dodge, Faribault, Fillmore goodhue, Hennepin, Houston, LeSueur, Olmsted, Ramsey, Rice, Scott, Wabasha, Washington, Winona, and Wright.