Figure 4. Seroconversion and persistent positivity for avian influenza virus (AIV) A subtypes based on HI titers in a cohort study in China during December 2014–April 2016. Each dot and line connection represents 1 participant. Red dashed lines represent positive cutoff for the HI titers; HI–positive samples were confirmed by a microneutralization assay. A) Comparison of paired samples from participants during 2 surveillance periods showing seroconversion for 6 AIV subtypes. Weighted lines and dots represent participants with seroconversion. B) Number of participants with >2 positive sample who were persistently seropositive for 6 AIV subtypes. Weighted lines and dots represent number of participants with seropositivity. C) Antibody titers of representative participants with >1 positive sample in the 4 serosurveys. HI, hemagglutinin inhibition.