The three children from Webster and Hamilton counties did not need hospitalization and have recovered from the illness.
The Iowa Department of Public Health said Tuesday the A/H3N2 strain of the virus is similar to a strain that circulated in the 1990s, The Des Moines Register reported Saturday. People in Pennsylvania, Maine and Indiana have also reportedly been sickened by the strain.
Dr. Patricia Quinlisk, medical director of the Department of Health, said people exposed to the 1990s virus should have some residual immunity and the current flu shot should increase that protection. H3N2 is causing less concern than the 2009 outbreak of H1N1 -- or swine flu -- but state health authorities are keeping a watch on north-central Iowa for any further cases.
"The H1N1 virus was different because it was very new and it seemed to spread very easily from person to person," Quinlisk said.
The Health Department reported in previous cases of H3N2 infection people had direct contact with pigs, though none of the recently ill children had such contact.