Flu is an almost mundane reality of human existence, a routine illness that leaves a substantial portion of the human population feeling miserable each year as flu season rolls around. This banal predictability hides a much more nefarious reality: flu is among the most dangerous pathogens we live with in modern society.

Many people think that the flu is just a bad cold. In reality it is so much more. A cold is an annoyance, whereas the flu is a more serious virus that can do real damage.

“People think of flu as the common cold,” says Kristine Sheedy, who heads the H1N1 vaccine communication task force for the CDC. “It’s not the common cold. It can be deadly.” (Sternberg, 8-28-2009) In an average year the flu kills up to 50,000 Americans, including 100-300 children. Many of these deaths involve normal, energetic little kids who were otherwise healthy before they got the flu.

What is the flu?

Influenza is a virus in the form of RNA, loosely connected into chromosomes. When a virus infects a cell, its chromosomes essentially fall apart into a mess, which is copied to make more viruses that then enter the bloodstream to spread throughout the body. Along the way in this copying process, any other genetic material that may be lying about within the cell is also stuffed into the thousands of viral copies that are made. It’s in this way that the virus can pick up the host’s genetic material and rapidly mutate. When two different types of flu viruses get into an animal cell at the same time, they can swap chromosomes to create new strains of the virus. (Garrett, 2009)

When is fl season?
The so-called flu season typically starts around October and peaks between December and February, but it can also extend beyond that. Viruses don’t do well in sunlight, which is why people get sick less often over the summer.

Flu mutations
Flu mutates at some of the fastest known rates for any virus. Because the flu virus mutates so easily, it can be especially frustrating for medical experts trying to contain it. “We joked that the influenza virus is listening in on conference calls,” says Daniel Jernigan, who directs the CDC’s Influenza Division. “It tends to do whatever we’re least expecting.” (Yang, 2018)

Flu viruses have 8 RNA segments. If more than one virus infects a single cell, the viruses can swap some of these RNA segments, giving rise to unique mutations. It’s this constant reshuffling that makes it so dangerous and difficult to treat.

In 2 years time, one particular strain of the flu virus jumped from 1% resistance to Tamiflu to 99% resistant. (Szabo, 5-14-2009) And some of these mutations can prove deadly. A little tweak that bumps the lethality rate to 1% or 2% would create an epidemic that would wipe out millions of people.

This variability is also why some individuals are affected more during certain flu seasons than others. Somebody who’s had the flu without incident several times before may be put on their death bed because a particular strain happens to attack a unique genetic vulnerability.

Flu complications & dangers

The primary danger is that a flu infection can make it easier for bacteria to invade the bloodstream, leading to bacterial pneumonia that can trigger sepsis. Those with pre-existing heart or lung conditions (such as asthma) are at particular risk, as is anyone with a weakened immune system.

Ironically, most fatal complications arise because the immune system overreacts, triggering an exaggerated inflammatory response that causes viral pneumonia, organ damage or sepsis. (McKay & Toy, 2018) So it isn’t the virus itself that kills, but an overreaction to the virus by a person’s own immune system.

How Flu Spreads
Flu viruses move person to person through physical contact, such as handshaking or touching contaminated surfaces like doorknobs or counter tops. The good news is that most influenza strains, including H1N1, are relatively fragile outside the host. They don’t live long and are easily destroyed by disinfectants. (Sanders, 2-27-2010)

Up until recently it was assumed that flu only spread through physical contact and wasn’t an airborne pathogen. We now know that not to be the case. It can be spread via airborne droplets at a distance of 3 to 6 feet. “That’s the breathing zone,” says Dr. William Schaffner, an infectious disease specialist. “When I breathe out, if I’m infected, what you inhale contains the flu virus.” (McGinty, 1-15-2019)

A recent study found that around half of flu cases are spread via tiny airborne particles, contradicting previous beliefs that the flu is hardly ever spread that way. By comparing two groups of people, one group equipped with soap and masks and the other not, they were able to infer that aerosol transmission caused between 33% and 92% of cases in Hong Kong and 55% to 98% Bangkok. People who caught the flu via the airborne route were also more likely to develop classic flu symptoms, whereas those who got sick via large droplets tended to have milder symptoms. (Hesman-Saey, 2013)

It takes 24 to 48 hours after transmission for the symptoms to set in. During this time a person can spread the flu without even knowing they are sick.

The spread of a virus is measured by what is known as a reproduction rate. A reproduction rate of 1.0 means that each person infected will spread it to 1 other person. The 2009 H1N1 pandemic had a reproduction number of 1.4 to 1.5. This may not seem like much, but it was enough to eventually infect 24% of the world’s population. (McGinty, 2019)

How to avoid catching the flu
It’s not as easy to catch the flu as one might think. In order to get sick, say doctors, it’s usually necessary for germs to enter your nasal passages or get into your tear ducts. Germs that get into your body through a cut can’t make you sick, and viruses that enter your mouth are generally killed by oral secretions. This is why health officials are always advising that you wash your hands and avoid touching your eyes and nose. Washing hands frequently keeps the germs off, so that when you rub your eyes you don’t get infected. Of course, the problem is that considering the amount of things both we and our children touch, and the amount of times our hands will go to our nose or eyes or face, there are plenty of opportunities for the virus to spread.

Additional information on the flu: