ferret serum after infection allowed the identification of two very different antigenic influenza type B variants in the years 1988 – 1989. These viruses shared antigens with either B/Yamagata/16/88, a variation that was discovered in Japan in May 1988, or B/Victoria/2/87, the most recent reference strain. The B/Victoria/2/87 virus shared antigens with all influenza B viruses discovered in the United States during an outbreak in the winter of 1988 – 1989. In Japan, influenza B virus reinfection was investigated virologically in 1985 – 1991 and epidemiologically in 1979 – 1991 in children. Four influenza B virus outbreaks that each included antigenic drift occurred during the course of this study. Between the epidemics in 1987 – 1988 and 1989 – 1990, there was a significant genetic and antigenic change in the viruses. Depending on the influenza seasons, the minimum rate of reinfection with influenza B virus for the entire period was between 2 and 25%. Haemagglutination inhibition assays were used to examine the antigens of the influenza B virus primary and reinfection strains that were isolated from 18 children between the years of 1985 and 1990, which encompassed three epidemic periods. The findings revealed that reinfection occurred with the viruses recovered during the 1984 – 1985 and 1987 – 1988 influenza seasons, which belonged to the same lineage and were antigenically close. Today, reinfection continues as increased influenza activity was reported in the United States in November 2022 due to the winter weather. References External links Influenza Research Database Database of influenza genomic sequences and related information. Viralzone: Influenzavirus B Orthomyxoviridae Influenza de:Influenzavirus#Influenza-B-Subtypen