Darron Cummings, Associated Press
In this Sept. 16, 2014 file photo, a sign telling customers that they can get a flu shot in a Walgreen store is seen in Indianapolis.

This year will mark the 100th anniversary of the great flu pandemic that killed an estimated 50 million people worldwide. About one-fifth of the world’s population became sick; some died within hours of experiencing their first symptoms.

The point of remembering this is not to scare readers. It is, however, intended to instill a healthy respect for the flu, which even in normal years kills about 36,000 people nationwide, according to the Centers for Disease Control and Prevention.

The flu virus mutates constantly, which is why new vaccines are produced each year. One year it may indeed mutate into a strain as deadly as the one in 1918, but health officials are not predicting such a thing this year.

However, as 2017 came to a close, this season’s variety of flu was beginning to prove troublesome. Cold weather in much of the nation, which forces people indoors where germs more easily spread, and a vaccine that this year is believed to be only 10 to 33 percent effective, are being blamed.

The CDC said the virus already is widespread in 36 states. Utah isn’t one of them. The state’s Department of Health issues a weekly influenza report. The most recent one, for the week ending Dec. 30, showed a high activity of flu-like illnesses in Davis and Bear River counties only. Southern Utah had low to minimal reports of such illnesses. The rest of the state reported minimal cases, including Salt Lake County.

That doesn’t mean people should let down their guard. Health officials say it’s hard to know how reliable such reports are because most people do not go to the hospital to be tested when they get the flu. In some parts of the country, however, cases are being reported at twice the rate of a year ago.

Also, peak flu season tends to be in February, so it’s early yet.

We know you have heard the preventative measures before, but they are worth repeating. Wash your hands frequently, avoid contact with people who are experiencing flu symptoms. And, if you haven’t already, get vaccinated.

That may sound like contradictory advice, considering how apparently ineffective this year’s virus is. But Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, told USA Today that it’s difficult to accurately calculate the effectiveness of a vaccine.

Strains other than the dominant one also can produce influenza, and the vaccine may be effective against those. Also, vaccinated people who do become sick tend to have mild symptoms, and they are less likely to develop pneumonia, which often is to blame for flu-related deaths.

That progression to pneumonia apparently was the case with Alani “Joie” Murrieta, a 20-year-old mother of two who, according to the Washington Post, contracted the flu at Thanksgiving and died two days later.

Cases such as this happen each year. The young and the elderly are particularly vulnerable.

Yes, it is true that 1918’s pandemic had some unique factors. The unsanitary conditions connected with World War I helped it to spread, as did the many soldiers who returned home worldwide at the end of that conflict.

This year isn’t likely to be anything like that one. But any disease that kills 36,000 per year on average should not be taken lightly.