Though the calendar today says spring, the flu season is still hanging on to some winterlike activity, though overall markers continued to decline, according to the latest update from the US Centers for Disease Control and Prevention (CDC).
The agency said in an accompanying analysis that flu activity has been elevated for 17 straight weeks, which is longer than a typical flu season but expected, given the season's early start.
In another unusual wrinkle to the current flu season, CDC experts are looking into reports of morbilliform rash from several states in people with lab-confirmed flu, mostly influenza B.
A CDC flu division official said in a Mar 18 ProMed Mail post that the numbers of reported flu-linked rashes have small so far, but the CDC was concerned that influenza B, potentially with rash, could be increasing over the coming weeks. She noted that rash is an uncommon flu complication, very rarely seen with influenza B.
Canadian researchers in a ProMED Mail post yesterday pointed out a case series of measles-like rashes was linked to a school influenza B outbreak last spring in a rural British Columbia community.
Sharon Hoskins, a CDC press officer, told CIDRAP News that the investigation has just started and that the agency doesn't know much yet, other than the reports by multiple people in multiple states. Last month the CDC said it was probing reports of swollen salivary glands (parotitis) in people with flu, mainly children who had H3N2 infections.
Rise of influenza B
In its weekly FluView report today, the CDC noted that influenza B strengthened its domination over other flu strains last week, rising to 67% of all flu detections and becoming the dominant strain in 7 of the CDC's 10 regions, most of them in the south, Midwest, and east. The percentage of respiratory specimens testing positive for flu fell slightly, to 11.2% last week, from 11.4% the week before.
Nationally, the percentage of clinic visits for flulike illness fell slightly to 2.3% from 2.4%, but it is still above the national baseline of 2%. Eight of the CDC's 10 regions are still above their baselines, the same as the week before. The number of states reporting high activity declined to just Puerto Rico and four states: Arkansas, Kansas, Mississippi, and Oklahoma.
Widespread flu was reported by seven states, two fewer than the week before, with most of them located in the northeastern part of the country.
One flu marker that continues to rise is the rate of hospitalizations for flu. The overall number rose to 57.1 per 100,000 population, up from 55.7 per 100,000. And for seniors—the hardest hit group—the rate climbed to 284.3 per 100,000, the highest the CDC has seen since it started tracking flu hospitalizations in adults in 2005. In the previous week it was 277.9 per 100,000 in that age-group.
For deaths, the overall percentage from pneumonia stayed at 7.6%, still above the epidemic threshold. Three more pediatric flu deaths were reported, raising the season's total to 107.
Mar 20 CDC FluView
Mar 20 CDC flu situation update
Mar 18 ProMED mail post
Mar 19 ProMED mail post