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

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.

[Efficacy of fish as predators of Aedes aegypti larvae, under laboratory conditions]. / Competência de peixes como predadores de larvas de Aedes aegypti, em condições de laboratório.

OBJECTIVE: To evaluate the efficacy of fish as predators of the Aedes aegypti larvae in laboratory conditions. METHODS: The male and female of five different fish were included in the experiment. The tests to measure their consumption ability lasted five weeks for each species. Each trial involved four test tanks and four control tanks. Two control tanks contained just one fish, and the other two just larvae. Each of the test tanks contained one fish and the larvae. During the first week, 100 larvae were placed in the tank, with an additional 100 added every week, up to a maximum daily amount of 500 larvae. The length and weight of the fish were measured at the beginning and end of every week. RESULTS: A total of 369,000 larvae were used. The Trichogaster trichopteros was the only species in which both sexes ate 100% of the available larvae. The Betta splendens failed to eat only 15 larvae. The male Poecilia reticulate showed a strong capacity for larvae eating, compared with the female of the same species. In terms of weight and size, the Betta splendens proved capable of eating 523 larvae per gram of weight per day. CONCLUSIONS: The female and male Trichogaster trichopteros and Astyanax fasciatus, and the female Betta splendens and Poecilia sphenops proved to be the most effective predators of the Aedes aegypti larvae. And although the male Poecilia sphenops and female Poecilia reticulata were less effective, they were also capable of eradicating the total number of Aedes aegypti larvae that could appear over 24 hours in a breeding site under natural conditions. The male Poecilia reticulata, however, proved incapable of doing so.