Influenza

Influenza is not a joke. Commonly called the flu, influenza is a highly contagious virus that usually causes mild to severe respiratory illness but can also lead to death.¹ Don’t be confused, though: the flu is different from a cold. The flu usually comes on suddenly, with symptoms such as fever, cough, sore throat, body aches, and fatigue.¹

According to the CDC, “Most experts believe that flu viruses spread mainly by tiny droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose or possibly their eyes.”²

Types of Influenza

There are actually four different types of influenza viruses: A, B, C, and D. Influenza types A, B, and C can cause illness in humans. But types A and B cause seasonal epidemics or respiratory illnesses nearly every year.³ Influenza A can be found in many species, including humans, birds, and pigs.⁴ Influenza B is typically only found in humans and can only be passed from human to human.⁴ Influenza C mainly occurs in humans but has been known to also occur in dogs and pigs. Influenza D is found mainly in cattle. It’s not known to infect or cause illness in humans.³

The most common influenza A has several subtypes that circulate seasonally in humans: H1N1, H2N2, and H3N2. These three subtypes are based off of the combination of two proteins on the viral surface: hemagglutinin (H) and neuraminidase (N). There are 18 different H subtypes and 11 different N subtypes.³

Studies have shown influenza B and influenza A can be equally severe, challenging a previous misconception that type B tends to be a milder disease.⁵ Influenza type C infections generally cause mild illness and are not thought to cause human flu epidemics.³

The CDC estimates that each year from 2010 to 2020, influenza infection resulted in 9 – 41 million illnesses, 140,000 – 710,000 hospitalizations, and 12,000 – 52,000 deaths.⁶ Data for the 2017 to 2018 influenza season indicates that 84.1 percent of positive samples were influenza A, while 15.9 percent were influenza B. Among hospitalizations, 86.4 percent were associated with influenza A, while 13.2 percent were associated with influenza B infection.⁷

Flu vs. COVID-19 and Other Illnesses

But how does the influenza compare to COVID-19? COVID-19, caused by the novel coronavirus (SARS-CoV-2), and the flu are both respiratory illnesses. While there’s a lot of symptomatic overlap between them, there are also key differences in the symptoms, incubation period, severity of the disease, hospitalization rates, and your body’s immune response.⁸

Influenza and the common cold are both contagious respiratory illnesses as well, but they are caused by different viruses. The flu is caused by influenza viruses only, whereas the common cold can be caused by a number of different viruses, including rhinoviruses, parainfluenza, and seasonal coronaviruses.

Because flu and the common cold have similar symptoms, it can be difficult to tell the difference between them based on symptoms alone. In general, flu is worse than the common cold, and symptoms are typically more intense and begin more abruptly. Colds are usually milder than flu, and people with colds are more likely to have a runny or stuffy nose than people who have flu. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.⁸

While influenza is usually an upper respiratory tract infection, pneumonia is an infection of the lower respiratory tract. Severe influenza can lead to pneumonia, as can other viruses, bacteria, and fungi.¹⁰

Influenza? How Can You Tell?

This respiratory season, influenza may be circulating alongside SARS-CoV-2 and other common respiratory viruses. Because of their similar and overlapping symptoms, it’s nearly impossible to know what’s causing a respiratory infection without diagnostic results. BioFire’s syndromic infectious disease testing approach can help eliminate the guesswork. Syndromic testing is the process of using one test to simultaneously target multiple pathogens with overlapping signs and symptoms.

The multiplex PCR BioFire^® Respiratory 2.1 Panel accurately detects and identifies the pathogens most commonly associated with respiratory infections—including influenza A, influenza B, SARS-CoV-2, rhinoviruses, parainfluenza, seasonal coronaviruses, and many other common respiratory viruses and bacteria. The BioFire RP2.1 Panel offers results in about 45 minutes.

At the point-of-care, the BioFire^® Respiratory 2.1-EZ Panel (EUA)* provides answers on a comprehensive menu of respiratory pathogens for patients suspected of a respiratory infection consistent with COVID-19. The BioFire RP2.1-EZ Panel (EUA) is authorized for use at the point of care (POC) in patient care settings operating under a CLIA Certificate of Waiver, Certificate of Compliance, or Certificate of Accreditation.

Rapid results from BioFire’s respiratory panels may enable better-informed diagnosis and treatment of patients. These comprehensive results may also help clinicians make patient management decisions around admissions, isolation, and additional diagnostic testing.

References

Cold Versus Flu. Accessed on 16 September 2021. Retrieved from: https://www.cdc.gov/flu/symptoms/coldflu.htm
Key Facts about Influenza. Accessed on 21 Sept 2021. Retrieved from: https://www.cdc.gov/flu/about/keyfacts.htm
Types of Influenza Viruses. Accessed on 21 Sept 2021. Retrieved from: https://www.cdc.gov/flu/about/viruses/types.htm
Influenza in Animals. Accessed on 6 October 2021. Retrieved from: https://www.cdc.gov/flu/other/index.html
Su S, et al. Clinical Infectious Diseases, Volume 59, Issue 2, 15 July 2014, Pages 252–255.
Disease Burden of Influenza. Accessed on 21 Sept 2021. Retrieved from: https://www.cdc.gov/flu/about/burden/index.html
Update: Influenza Activity — United States, October 1, 2017–February 3, 2018 Accessed on 21 Sept 2021. Retrieved from: https://www.cdc.gov/mmwr/volumes/67/wr/mm6706a1.htm?s_cid=mm6706a1_w
Cold Versus Flu. Accessed on 21 Sept 2021. Retrieved from: https://www.cdc.gov/flu/symptoms/coldflu.htm
Mayo Clinic. COVID-19, cold, allergies and the flu: What are the differences? Accessed on 27 Sept 2021. Retrieved from: https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/covid-19-cold-flu-and-allergies-differences/art-20503981
The Causes of Pneumonia. Accessed on 5 October 2021. Retrieved from https://www.cdc.gov/pneumonia/causes.html

*This product has not been FDA cleared or approved, but has been authorized for emergency use by FDA under an EUA for use by authorized laboratories;
*This product has been authorized only for the detection and differentiation of nucleic acid of SARS-CoV-2 from multiple respiratory viral and bacterial organisms; and,
*The emergency use of this product is only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 360bbb-3(b)(1), unless the declaration is terminated or authorization is revoked sooner.

Influenza

Types of Influenza

Flu vs. COVID-19 and Other Illnesses

Influenza? How Can You Tell?

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