The national influenza forecast has been updated. We are projecting excellent vaccine coverage for the first 2/3 of the season, but a moderate probability of decreased vaccine efficacy is expected beginning in March. Seasonally early laboratory-confirmed influenza type A/B positive pediatric cases were documented in our county several weeks ago. The Pacific Northwest, an area of the country associated with pockets of lower influenza vaccine rates, has reported early appearance of influenza as well. This may be further evidence of a novel type A influenza virus (A/H3N2) that drifted. It was this genetic drift that prompted an update of this season’s influenza vaccine. We received report this virus overwhelmed several adult intensive care units in Australia and New Zealand. Had we no influenza vaccine available to the country, we would now be issuing a warning for influenza this year because of drifted A/H3N2. Therefore, we strongly advise vaccination of all patients for influenza this year.
We continue to monitor the situation regarding A/H3N2 variant, which is associated with 50 times the hospitalization rate and 12 times the fatality rate of pandemic H1N1. The bulk of documented transmission has been swine to human, with rare examples of limited human to human transmission. We have not observed additional transmission since the agriculture fairs, however are following the situation closely. As noted previously, it is unknown whether this virus will evolve to a more efficient human to human transmission form. If it does, the apparent case fatality rate is expected to drop substantially. For more information, please visit the CDC information page.