All About Influenza
What You Need to Know to Stay Healthy
Influenza is a well-known virus that packs a big punch, causing yearly outbreaks that sicken up to 1 in 5 Americans each year ¹. With so many respiratory viruses affecting us this season, it is important to recognize and treat the correct one.
There’s a lot to know about the flu. Influenza stands out because it changes constantly, making it tricky to fight and protect against.
Understanding how the flu works, especially the parts of the virus that help it spread, can help you stay ahead of it, protect yourself, and keep your loved ones safe. Keep reading to learn why the flu’s constant changes matter and how you can take action to stay healthy this season.
Why do people get the flu more than once?
The flu virus can change itself, which is also known as mutation. When the virus changes, your immune system might not recognize it anymore. This is why people can get the flu more than once and why vaccines are updated every year.
How does the flu change?
The flu mutates by changing its antigens. Antigens are like name tags on the flu virus that help your immune system recognize and respond to it.
These mutations happen frequently through small changes over time, but sometimes large changes can create new strains of the flu which cause outbreaks.
An example of a small change is seasonal variation, when flu A changes from one flu season to the next. Larger changes, or antigenic shifts, can happen when flu A mixes with an animal flu.
Avian flu, for example, becomes a concern because of its potential to swap antigens with human flu. This process, called re-assortment, can lead to new strains which may be dangerous.
There are two main antigens scientists look at:
- Hemagglutinin (H): This helps the virus get into your cells.
- Neuraminidase (N): This helps the virus spread from one cell to another.
These two antigens come in different types, like tags of different shapes and colors. For example:
- H3N2: This means it has type 3 hemagglutinin and type 2 neuraminidase.
There are 18 different H subtypes and 11 different N subtypes, which means that flu antigens have many different combinations.
What are the symptoms? Is the flu dangerous?
Yes, the flu can be dangerous, especially for certain groups of people. Normal symptoms of the flu include fever, chills, cough, sore throat, runny nose, body aches, fatigue, and sometimes vomiting or diarrhea. While many recover within a week or two, the flu can cause severe complications like pneumonia, heart inflammation, or worsening of chronic conditions such as asthma.
Older adults, young children, pregnant women, and people with chronic or underlying conditions are at higher risk.Each year the flu causes up to 200,000 hospitalizations and 36,000 deaths, making prevention and early treatment essential to keeping our community healthy ¹.
While symptoms can be similar, the flu is generally more severe than the common cold.
This table provided by the Centers for Disease Control and Prevention can help you better understand the difference between them ².
| Signs and Symptoms | Cold | Influenza (Flu) |
| Symptom onset | Gradual | Abrupt |
| Fever | Rare | Common; lasts 3-4 days |
| Aches | Slight | Common; often severe |
| Chills | Uncommon | Fairly common |
| Fatigue, weakness | Sometimes | Usual |
| Sneezing | Common | Sometimes |
| Chest discomfort, cough | Mild to moderate; hacking cough | Common; can be severe |
| Stuffy nose | Common | Sometimes |
| Sore throat | Common | Sometimes |
| Headache | Rare | Common |
How does the flu spread?
The flu spreads mainly through respiratory droplets when an infected person coughs, sneezes, or talks.
These droplets can travel through the air and be inhaled into your lungs.
The virus can also spread by touching surfaces or objects contaminated with flu germs and then touching your mouth, nose, or eyes.
Flu spreads easily in crowded places, so good hygiene and yearly vaccination are necessary to prevent it.
Why should I get tested for the flu if I have symptoms?
Getting tested for the flu confirms whether your illness is caused by the flu or another condition, like COVID-19 or a bacterial infection.
A proper diagnosis ensures you receive the right treatment, such as antiviral medications that work best when started early.
It can also prevent unnecessary antibiotics, which don’t work on viruses, and helps protect others by identifying contagious cases.
Key Facts
- Flu viruses have “name tags” (antigens) that help your body recognize the virus.
- Flu viruses change their antigens often, which is why vaccines and treatments must change too. It’s also why you can get the flu more than once.
- Getting vaccinated each year is the best thing you can do to protect yourself and others. The flu can be dangerous for certain groups of people, like older adults and young children.
- If you have symptoms, getting tested can help you receive the proper treatment.
By understanding how the flu works, you can better understand why staying updated on vaccines is important. If you have symptoms, visit your healthcare provider to find the cause of your illness.
There are treatments available and identifying the right pathogen will help your doctor prescribe the right medication.
Don’t forget to visit HNL Lab Medicine to complete your lab tests. Stay protected with vaccines, seek answers for your symptoms, and trust HNL Lab Medicine for quality lab results!
REFERENCES
¹ National Institutes of Health. (2016, January 27). Influenza. U.S. Department of Health and Human Services. https://www.nih.gov/about-nih/what-we-do/nih-turning-discovery-into-health/influenza.
² Centers for Disease Control and Prevention. (2024, August 26). Signs and symptoms of flu. U.S. Department of Health and Human Services. https://www.cdc.gov/flu/signs-symptoms/index.html.