A study prepared by NIVEL (Saverio Caini et al) on the epidemiological and virological characteristics of influenza B, based on 935,673 influenza cases collected in twenty-six countries around the world, found that influenza B is a common disease, with a number of epidemiological differences compared to influenza A.
The study found that the median proportion of influenza cases caused by influenza B was 23%, with no statistically significant difference by world region. On average, influenza B was associated with lower maximum influenza-like illness rates compared to influenza A both in the northern hemisphere and in the southern hemisphere. Patients infected with influenza B were usually younger (5-17) compared with influenza A. An analysis of the circulating influenza B strains found that during seasons where influenza B was dominant or co-circulated (>20% of total detections), there were vaccine mismatches in roughly 25% of seasons.
These findings should be considered when optimizing control and prevention strategies in different regions of the world and reducing the global burden of disease due to influenza.
The paper was published in a Special Influenza Supplement of the Journal of Influenza and Other Respiratory Viruses. The Guest Editor for this Supplement is an epidemiologist working at NIVEL (John Paget).
For more information about the Global Influenza B study, see www.nivel.eu/gibs.