The prevalence of hemagglutination-inhibition (HI) antibodies to influenza viruses A/swine/ILL/63 and A/swine/Taiwan/7310/70 (H3N2) in Illinois swine herds--1971 to 1973.

Serum samples from 449 swine in 78 herds distributed in 28 counties in Illinois were tested for HI antibodies against A/Swine/Ill/63 and A/Swine/Taiwan/7310/70 (H3N2) from 1971 to 1973. No antibodies to the Taiwan strain were detected. A herd reactor rate of 42.3% and a prevalence rate of 25.4% against A/Swine/Ill/63 was detected. Age specific reactor rates were 6% for animals 12 months of age or under and 33% for swine 13 to 18 months of age.