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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

Luke T. Daum*, Linda C. Canas*, Catherine B. Smith†, Alexander Klimov†, William Huff*, William Barnes*, and Kenton L. Lohman*Comments to Author 
Author affiliations: *Brooks Air Force Base, San Antonio, Texas, USA; †Centers for Disease Control and Prevention, Atlanta, Georgia, USA;

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Table 2

Hemagglutination Inhibition Reactions of Influenza A(H1N1) Virusesa Reference Ferret Antisera

Reference Antigens Bei/262 NC/20 Bay/07 Joh/82
A/Beijing/262/95 640b 320 20 20
A/New Caledonia/20/99 160 320 10 <10
A/Bayern/07/95 40 10 1280 1280
A/Johannesburg/82/96 40 10 1280 1280
Test Antigens
A/Peru/1621/99 160 160 <10 <10
A/Peru/1798/99 160 160 <10 <10

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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