The epidemiological signature of influenza B virus and its B/Victoria and B/Yamagata lineages in the 21st century

Abstract

We describe the epidemiological characteristics, pattern of circulation, and geographical distribution of influenza B viruses and its lineages using data from the Global Influenza B Study. We included over 1.8 million influenza cases occurred in thirty-one countries during 2000–2018. We calculated the proportion of cases caused by influenza B and its lineages; determined the timing of influenza A and B epidemics; compared the age distribution of B/Victoria and B/Yamagata cases; and evaluated the frequency of lineage-level mismatch for the trivalent vaccine. The median proportion of influenza cases caused by influenza B virus was 23.4%, with a tendency (borderline statistical significance, p = 0.060) to be higher in tropical vs. temperate countries. Influenza B was the dominant virus type in about one every seven seasons. In temperate countries, influenza B epidemics occurred on average three weeks later than influenza A epidemics; no consistent pattern emerged in the tropics. The two B lineages caused a comparable proportion of influenza B cases globally, however the B/Yamagata was more frequent in temperate countries, and the B/Victoria in the tropics (p = 0.048). B/Yamagata patients were significantly older than B/Victoria patients in almost all countries. A lineage-level vaccine mismatch was observed in over 40% of seasons in temperate countries and in 30% of seasons in the tropics. The type B virus caused a substantial proportion of influenza infections globally in the 21st century, and its two virus lineages differed in terms of age and geographical distribution of patients. These findings will help inform health policy decisions aiming to reduce disease burden associated with seasonal influenza.

Decline in respiratory deaths not associated with influenza in Russia: effect of the introduction of the pneumococcal conjugate vaccine (PCV13), or improvement in care?

“…In particular, influenza B is characterized by the circulation of B/Yamagata and B/Victoria viruses. It is known that the age distribution for the B/Yamagata infections is notably older than for the B/Victoria infections [13,14].…”

La gripe: 76 años de vacuna antigripal… ¡y de la hemaglutinina!

“…Debido a la co-circulación habitual en la misma temporada de los dos "linajes" de virus B, Victoria y Yamagata, a la imposibilidad de predecir cuál de ellos será el dominante en una temporada dada (21) , y a las controversias en relación a la existencia de protección cruzada, han aparecido recientemente nuevas vacunas que incluyen a ambos tipos de virus A y B. Un punto destacable es que de promedio y a escala mundial los virus B suponen alrededor de un 23% de los aislamientos en una temporada dada (22) . El punto clave es, tal como se ha expuesto con anterioridad, si desde la perspectiva de salud pública y teniendo en cuenta el incremento de su coste económico, estaría plenamente justificado el paso de una vacuna trivalente a una tetravalente (23) .…”

Influenza-associated mortality for circulatory and respiratory causes during the 2013-2014 through the 2018-2019 influenza seasons in Russia

“…We note that there is a good temporal correspondence between the "bumps" in mortality rates and peaks of influenza circulation, save for the sizeable wave of influenza B/Victoria in 2017. The lack of the corresponding visual effect of influenza B/Victoria circulation on mortality may be related to the young age distribution for influenza B/Victoria infections (Methods; [21,22]). Figure 3 plots the fits for the model for respiratory mortality given by eq.…”