Map shows Washington counties hit hardest by flu in 2016-2017's deadly season

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It’s early in the winter, but the flu season rages in almost every state – including Washington state.

With the increase in local cases in hospitals and clinics over the last three weeks, the Centers for Disease Control reported on Wednesday that the flu in Washington is now widespread.

It comes on the heels of the deadliest flu season so far this decade when more than 250 people died. Here’s a look at the deaths last year by county.

When looking into why the deaths are highest in Snohomish, Pierce, and King counties, health leaders say that they look at the population and consider vulnerable individuals within it.

Most people who died last season – from October to May – were over 65 years old.

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“One very important reason that King County would have more flu deaths is that our population is almost a third of the state total – and so we’d expect to see about a third of all deaths in the state,” public information officer Hilary Karasz told KIRO 7. “And, it’s super important to remember that not all flu deaths are reported, so the numbers across the state are likely underreported.”

The state changed the way it tracked flu deaths after the 2009-2010 season with the H1N1 pandemic. Despite hospitalizations trending downward in King County and elsewhere, reported flu deaths have been on the rise statewide. As death totals hit over 100 people in the 2014-2015, the H3N2 strain was starting to become the predominant flu virus in Washington.

There are multiple known strains of the flu: Influenza A (H1N1), influenza A (H3N2), and influenza B viruses.Typically, H3N2 brings a more severe flu season. It’s a type that is associated with higher levels of hospitalization and deaths.

H3N2 is the predominant strain for the current season, again. Health leaders encourage people – especially the elderly, the very young, and people with underlying conditions – to get the flu shot, even if we don’t know how well it will match the flu viruses throughout the season.

"Last year in the U.S., vaccine effectiveness for influenza A H3N2 was 34%, and there have been no significant mutations detected in this strain since the last season," King County Health Officer Dr. Jeff Duchin wrote in a blog post. "The bottom line is that even though we cannot predict which strains will predominate in the U.S. this season, it is likely that influenza vaccination will provide meaningful protection against severe illness, hospitalization and death."

KIRO 7 News asked about the trends in people getting the flu shot, but Washington State Department of Health said it does not have complete statistics for adults who have or have not received it.

The group hit hardest by the flu are older people who do not respond well to the vaccine, according to Duchin.

Of the 14 confirmed flu deaths this 2017-2018 season,  the people who died are mostly in their 70s, 80s, or 90s. Here's the break-down by county so far.

The CDC does not count the number of flu deaths nationwide. Based on death certificate data and weekly influenza virus surveillance information, approximately 20,000 flu-related deaths annually in the United States.

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