Volume 8, Number 4—April 2002
Genetic and Antigenic Analysis of the First A/New Caledonia/20/99-like H1N1 Influenza Isolates Reported in the Americas
aTest viruses are considered antigenically similar to the reference strain if the H1 titer is equal or two times lower than the homologous titer of the reference virus. If the difference in H1 titers is 4-fold or higher, the test viruses are considered to be antigenically different from the reference strain.
bBold and underlined values represent homologous H1 titers.
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