By Jonny Lupsha, News Writer

Flu deaths in the United States have doctors encouraging the public to get the flu shot now, Fox News reported. An estimate of 1,300 deaths have been reported so far, with another 23,000 hospitalizations reported. Why is influenza still such a problem—and such a big one?

According to Fox News, the flu season in Australia started two months early this year, and United States flu trends often follow those of Australia. A related report released by the Center for Disease Control and Prevention (CDC) said that over two-thirds of flu diagnoses this year have come from influenza B of the virus, and out of those, 97 percent are of the so-called “Victoria lineage” of the flu. What is it about the flu that still raises such a stink after all these years?

The Flu 100 Years Ago

It’s easy to downplay the flu since medicine has come so far in the last 100 years. Nowadays, we often think of it as little more than a nuisance. We’re familiar with having to use some sick days for work, feeling feverish and achy for the better part of a week, sometimes getting a shot that might prevents the flu, and so on. However, a look back at the Influenza Pandemic of 1918 proves that the flu can be much more than just a nuisance and actually cause a substantial number of deaths.

“The attacks of flu occurred in waves—in mid-1918, then again in the spring of 1919,” said Dr. Barry C. Fox, Clinical Professor of Infectious Disease at the University of Wisconsin School of Medicine and Public Health. “Between 30 and 50 million people died worldwide.”

That same year in Spain, Dr. Fox said, there was an influenza epidemic so serious that it left the country’s population growth trending in the negative. So how did yearly flu deaths drop from 30 million to 1,300 in just 100 years, especially since scientists at the time already understood germ theory?

“Most physicians at the time believed influenza was caused by a bacterium, not a virus, but autopsies had continually failed to produce identification of a bacterial germ,” Dr. Fox said. “Unfortunately, there was no flu vaccine in those days, and efforts to develop one had failed. Instead, quarantines were put in place and bans were placed on public gatherings as a deterrent to contagion.”

More people died from the Influenza Pandemic of 1918 than were killed in World War I.

Antigenic Drift and Shift

It’s common knowledge that the flu mutates, which makes it so hard to isolate and eradicate, but the nature of this is far more involved than simple mutation.

Viruses like the flu are often classified by the specific types of hemagglutinin and neuraminidase proteins they possess. One of the most popular combinations of these—especially during the recent bird flu and swine flu panics—is referred to as “H1N1,” meaning “hemagglutinin type 1, neuraminidase type 1.” Dr. Fox said there are 16 types of hemagglutinin and nine types of neuraminidase, and flu viruses can have any one of each.

The flu’s prevalence is also related to its antigenic drift and antigenic shift.

“Antigenic drift is a process in which mutations to the virus genome produce changes in the viral H or N proteins,” Dr. Fox said. “This drift results in the emergence of new strains when either the H or the N protein undergoes minor changes—for example, H1N1 to H1N2. This is why the flu vaccine contains a different mix of viruses each year and must be updated manually; [but] because this is a single mutation, usually our bodies recognize at least one of the two proteins.”

Antigenic shift, on the other hand, is a much different beast with which we must contend, and Dr. Fox said it’s the reason disease pandemics occur.

“Instead of modifying the existing H and N proteins, the proteins are replaced by significantly different Hs and Ns—for example, H1N1 to H5N2,” he said. “This means that our bodies do not recognize either of these new Hs and Ns and, therefore, we don’t have any pre-existing antibody to protect against them.”

As the world trudges through another flu season, knowing the dangers and nature of the flu can inspire us to take proper precautions against it.

Dr. Barry Fox contributed to this article. Dr. Fox is a Clinical Professor of Infectious Disease at the University of Wisconsin School of Medicine and Public Health. He received his undergraduate degree in Molecular Biophysics and Biochemistry from Yale University and his medical degree from Vanderbilt University. He is board certified in both Internal Medicine and Infectious Disease.