The flu is an unpredictable virus that can either be a short seasoned, quick-passing event or -- like so far this year -- can be aggressive and deadly.
The Centers for Disease Control and Prevention (CDC) has reported that both hospitalizations and death because of the flu are higher than what is traditionally happening for this time of the year. More curious, is that it is increasing in demographics not traditionally seen as high-risk: the recent case of a 27-year-old woman dying after contracting flu followed on the heels of a healthy bodybuilder passed days after flu diagnosis.
Researchers believe that the particular strain of flu this season has been both stronger than expected, but also different than projected -- which caused immunizations to be less effective.
Dr. Amesh Adaljia, of Johns Hopkins Center for Health Security, said that the flu circulating right now is quite dangerous.
"This year is particularly bad because it's dominated by the H3N2 [flu strain], which tends to be more severe and causes more severe symptoms than other strains of flu," Adalja told Live Science.
Dr. Tom Frieden, director of the CDC, said at a news conference in early December that H3N2 seasons have historically been more deadly than others.
"We cannot predict what's going to happen in the rest of the flu season, [but] it's possible that we may have a season that is more severe" than usual," he said.
How the flu kills, is surprisingly multi-faceted, and generally fairly quick.
The most usual way is that the virus will make high-risk groups of people, like the elderly, more susceptible to other health problems. It is then those other factors that more directly lead to death.
According to the Mayo Clinic, pneumonia is the most serious complication of the flu, and it can often be deadly.
When a person that already has the flu then contracts pneumonia it is more aggressive and deadly because it is caused by a bacteria and not a virus. It is then considered a secondary infection and can take about a week to actually become deadly, because it takes times for that infection to take hold.
Influenza can also be life-threatening because it will create inflamation of critical organs, like the brain, heart, or other muscle tissues. It can also create a body-wide infammatory response, also known as sepsis, that is also a regular cause of death.
In addition to pneumonia and sepsis, there is a risk that organs will simply shut down or not work properly as the body fights the virus.
The 2017-18 flu season has been more harsh than normal -- and that can be blamed largely on the strain -- but there are preventative measures, some as simple as washing hands, can help keep more people healthy as traditional methods, like a flu shot, have been less effective this year due to circulation not matching up with strain this season, or the genetic changes that can happen with the virus.