(CNN) -- Three people appear to have become infected with a strain of influenza after exhibiting pigs or visiting the swine barn at the Minnesota State Fair, health officials said Friday.
Only one of the three cases has been confirmed to be an infection of the influenza variant H1N2, and test results are pending for the other two people, Minnesota health officials said.
"The H1N2v strain is different from the H3N2v strain that has prompted stepped up surveillance and prevention efforts nationwide, after causing 289 reported cases of illness and one death since the beginning of the year," state health officials said in a statement.
A teenage girl was confirmed to have the virus after she saw the pigs at the fair and became ill on August 26, officials said.
The other two cases involve an elementary-school-aged boy who became ill on August 27 after spending all day in the swine barn three days earlier and a woman in her late 70s who became ill on August 26 after spending a prolonged time in the swine barn and at the swine show in the Exhibit Hall on August 24, officials said.
The boy and woman had underlying health conditions and were treated with antiviral drugs, officials said. The woman was hospitalized and released.
All three patients have recovered or are recovering.
"For the past two weeks, we have been looking very hard for cases of influenza in people who have been exposed to swine," said Richard Danila, deputy state epidemiologist. "It is because of this careful surveillance that these cases have come to our attention.
"Right now, we don't have any basis for changing our recommendations to the public," Danila added.
Official are asking individuals at high risk for severe influenza to avoid swine contact at exhibitions, fairs and other venues, including the swine barn at the state fair. High risk individuals include children 5 or younger, pregnant women, people 65 or older, and those with chronic medical conditions, officials said.