Every Year, We Are Reminded Both Online and on the Evening

Every year, we are reminded both online and on the evening news of the deadly effects of the flu. There's no doubt that influenza is a killer. The Centers for Disease control estimates that 80,000 Americans died from the flu in 2017. But how can a simple case of the flu that many people recover from in a week or two be so deadly to others? Doctors who study the body's immune response cite three reasons. First, when the immune system is taxed, there is a good chance of co-infection with another germ-usually a bacterium, such as strep. Second, the flu can easily aggravate existing conditions such as heart disease and asthma. Third is the so-called cytokine storm. This is an overproduction of immune cells and their activating compounds (cytokines) in the lungs. The resulting lung inflammation and fluid buildup can lead to severe lung distress and can open the door to other diseases such as bacterial pneumonia.
What is the author's purpose in the first sentence of the passage?

A) To introduce a possible solution to the flu problem
B) To convince the reader to take steps to prevent the flu
C) To suggest that the flu is not as serious as some think
D) To connect the passage to the reader's frame of reference