The Lifecycle of the Flu

February 14, 2018


Most years, the terms “flu season” and “flu shot” are viewed as a pesky seasonal rite of passage, a nuisance, another thing on your to-do list. But this year, the virulent H3N2 virus — which has been circulating for 50 years and dubbed the “Hong Kong flu” — is getting peoples’ attention.

The 2017–2018 flu season epidemic is expected to kill more than 50,000 people 1 year or older, many of whom appeared healthy “just a few days” before they died. Being armed with knowledge and facts about the flu could mean the difference between life and death — and that’s no exaggeration.

Here’s what you need to know about the lifecycle of the flu.

Making Contact

People pick up the flu virus silently, without even realizing it. The virus can travel by air — up to six feet — often in the form of droplets when infected people (who may not know they are infected) cough, sneeze or even talk. The virus can also be transmitted in droplets on objects or surfaces.

  • The virus remains “live” and contagious on hard surfaces for up to 24 hours.
  • The virus remains “live” and contagious on soft surfaces, like tissues, for 15 minutes.
  • The virus lasts longer in cold, dry air, which is why flu spikes in winter. (Influenza’s original Italian name, influenza di freddo, means “influence of the cold.”)

The Attack

Once the flu virus enters your body, it heads straight for the respiratory tract, often ending up in the lungs. The virus clings to the cells and drops its genetic footprint into the cell’s nucleus, where it copies itself and eventually takes over the functions of the cell. When the cell finally dies, the copies are released into the body and begin infecting other cells. The replication process can last a few days, but you still may not feel like anything is wrong. You are contagious at this time. For how long?

  • Contagious period begins one day before symptoms develop.
  • Contagious period lasts up to five to seven days after becoming sick.
  • If you have any symptoms you are contagious.

Because a new flu lifecycle can start before you experience any symptoms, following a flu preventative routine at all times is critical to prevent the spread of the virus. Frequent hand washing, covering your nose/mouth when you cough or sneeze and avoiding people who are sick should be the standard.

Fighting Back

After about 48 hours, your body’s immune system recognizes those unwanted visitors and an army of white blood cells and antibodies fan out to fight the infection by swallowing or destroying infected cells. This is when you will begin to feel flu-like systems.

  • High fever
  • Sneezing/runny nose
  • Chills
  • Muscle/body aches
  • Fatigue
  • Sore throat

Unlike a cold, these symptoms often come on strong and suddenly. Take heart in the fact these symptoms mean your body is fighting back. Chemical messengers called cytokines and a series of proteins designed to kill infections trigger inflammation which causes symptoms; a fever can actually inactivate the virus (remember, it likes cold).

The best thing you can do at this stage is to get plenty of rest and drink plenty of fluids. Most of the time you can treat the flu at home with over-the-counter medications to treat your symptoms, such as ibuprofen/acetaminophen for fever, or hot tea and honey for a sore throat. You are highly contagious during this time, so you should stay home from work or school to avoid infecting others around you. If you must go out in public, wear a face mask to protect yourself and others.

*Caution: If flu symptoms appear and you are at risk of complications (age, chronic illness, weakened immune system), contact AFC Urgent Care right away. Taking antiviral drugs within the first 48 hours of noticing symptoms may reduce the length of your illness and help prevent more serious problems.


Flu symptoms usually last five to seven days, with the most severe symptoms in the first few days, although mild symptoms such as fatigue could last a week or two — so continue to take it easy. Again, if you are symptomatic, you are contagious. As your immune system gets the upper hand in killing off the infected cells, inflammation will go down and symptoms will subside. The good news is, as the battle between good and bad cells winds down, your immune system knows to leave some of those flu-fighting cells in your bloodstream with a memory of that specific virus, so if it returns, those infection-fighters will attack and destroy that virus quicker next time. This is also how the flu vaccine works.

Is it too late to get the flu shot?

No! The CDC recommends getting the flu shot, even during flu season. It takes about two weeks after vaccination for the body to produce the flu-fighting antibodies, so the earlier the better. However, with a record-setting season such as this one, the flu season could last well into May. Visit AFC Urgent Care today to get your flu shot and do your part to protect yourself and prevent the flu lifecycle from beginning again.


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