One of the difficulties of flu forecasting is that the dominant flu strain that shows up in North America, or in Europe, can differ greatly from the type (and severity) of flu that arrives in Russia, China, or the Middle East.
It is perfectly possible for North America to have an H3N2 flu season, while other parts of the northern hemisphere find themselves dealing primarily with H1N1 or Influenza B.And even when the subtypes do align, the strains within that subtype can vary considerably in terms of transmissibility, severity, and susceptibility to the current influenza vaccine.
In February of 2016 we saw reports of severe H1N1 flu in Russia and in a ECDC Risk Assessment : Reports Of Severe A(H1N1)pdm09 In Europe, prompting concerns it might make its way across the pond to North America.
As it turned out, 2016 proved to be an unusually mild year for flu in the United States, arriving late, and staying above the epidemic threshold for only a few weeks.Despite ominous warnings after Australia's severe flu season of what we should expect this winter, it is still anyone's guess how bad it will be. And the story here in the U.S. could differ greatly from what happens in Europe, or Russia.
The ECDC has prepared a RRA (Rapid Risk Assessment) for the EU/EAA on the soon-to-arrive 2017-18 flu season, that - not surprisingly - states that it is `impossible to predict the intensity or the peak of the influenza epidemic across Europe'.Despite ongoing concerns over the effectiveness of this year's vaccine (see ECDC: H3N2 Flu Vaccine Component Likely `Suboptimal'), today's report does offer some hope the season will be moderated by a carry over of community immunity from last year's H3N2 flu season.
20 December, 2017
Main conclusions and options for responseFollow this link to read the report in its entirety.
• The influenza season started in week 48/2017 with 11 EU/EEA countries reporting 10% or more sentinel specimens positive for influenza.
• First detections indicated circulation of A(H3N2) and B/Yamagata viruses. As the former subtype dominated last season, a high proportion of the population should be protected. However, the emergence of variant strains, as in the US, cannot be excluded and this would increase the likelihood of severe outcomes in the elderly.
• At this stage, it is impossible to predict the intensity or the peak of the influenza epidemic across Europe.
• Vaccine effectiveness against A(H1N1)pdm09 is expected to be high, whereas effectiveness against A(H3N2), the most prevalent type A virus, is likely to be low.
• B/Yamagata viruses are dominant so far, and vaccine effectiveness against this virus will be low as it is not included in the most widely used trivalent vaccine. Some effectiveness could be expected from cross-protection as a result of vaccination against B/Victoria virus.
• Regardless of vaccination status, the use of neuraminidase inhibitors and non-pharmaceutical measures in accordance with national guidelines or policy is encouraged.