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States Reporting Widespread Flu Nearly Doubles in One Week

Despite low flu vaccine effectiveness during Australia’s recent flu season, one new report indicates that the vaccine should be much more effective for the United States this season.

The number of states reporting widespread flu activity has nearly doubled this week, just 1 indicator of an intensifying flu season.

In the Center for Disease Control and Prevention’s (CDC) FluView report for week 50 ending December 16, 2017, 23 states reported widespread influenza. In the previous week, the flu was geographically widespread in just 12 states. During week 50, Puerto Rico and 23 states reported regional flu activity, while the District of Columbia and Delaware, Hawaii, Utah, and West Virginia reported only local flu activity. The proportion of outpatient visits for influenza-like illness (ILI) has reached 3.5%—up from 2.7% the previous week—and is continuing to climb above the national baseline of 2.2%. Influenza A viruses made up more than 86% of all influenza-positive respiratory specimens, with more than 88% of those being an H3N2 strain.

Following Australia’s recent severe flu season, marked by a record number of flu cases and low vaccine effectiveness, public health experts have warned that the United States may be in for a similarly rough flu season. A recent report published in the open access publishing platform F1000Research, however, indicates that the flu vaccine may end up being more effective for the Northern Hemisphere’s 2017-2018 flu season than it was in Australia, where the vaccine’s effectiveness was only 10% for the season. “It’s important every year that we monitor the Australian flu season because the following flu season in the United States and Europe could be similar,” said University of Texas Medical Branch professor and study author Slobodan Paessler, DVM, PhD, in a recent press release. “When the flu vaccine isn’t terribly effective in Australia, US and European health authorities prepare for a potentially severe flu season.”

This season, however, the new report suggests that Australia may not end up being such a flu harbinger. The H3N2 strain that recently caused a severe flu season in that portion of the Southern Hemisphere was different than the main H3N2 strain currently circulating in the United States.

Using a computer program to predict how well the current seasonal flu vaccine might protect against circulating strains, the report’s authors found that the vaccine is a better match to most of the H3N2 viruses prevalent so far in the United States this season. Last season the flu vaccine was about 43% effective against H3N2 in the United States, and the authors anticipate similar effectiveness this season. “Nevertheless, this situation could change if any of the viruses from the minority group, which are not covered by the vaccine, were to become dominant,” said the study’s authors. “For this reason, it’s very important that we closely monitor the evolution of the H3N2 flu viruses throughout the 2018 US flu season.”

Around the country, local health officials are continuing to respond to rising flu activity. The University of Chicago Medicine announced new temporary changes to its hospital visitor policy, restricting anyone with even mild flu-like symptoms from visiting to protect patients from getting sick. And, in San Diego County, which has already reported 3195 flu cases and 10 flu deaths this season, officials from the Health and Human Services Agency are reminding area residents to get vaccinated, especially those who are pregnant, have chronic health conditions, or are 65 and older. “The number of flu cases that are being reported is very worrisome,” said county public health officer Wilma Wooten, MD, MPH. “We urge the public to get vaccinated against the flu.”