Can You Have the Flu Without a Fever?

Medically Reviewed on 1/19/2022
flu symptoms
Since not every individual experiences all of the flu symptoms, it is possible to have the flu without having a fever.

Yes, it is possible to get flu without fever.

However, every flu symptom may not be seen in every individual.

Fever (oral temperature of 100°F or higher) is a defense mechanism launched by the body to halt the progression of the virus or the bacteria; however, every person has a specific reaction to the pathogen.

Some may develop all symptoms except fever, while others may feel feverish though the thermometer may not show fever. Additionally, some individuals may take over-the-counter medications for sore throat and runny nose, which may contain some amount of acetaminophen, so they may not develop a fever at all.

Are my symptoms flu or COVID-19?

It is impossible to clinically distinguish COVID-19 infection from seasonal flu. Therefore, if you have symptoms or a contact history, it is better to get tested for COVID-19.

  • You may choose to get tested at home (for both seasonal flu and COVID-19) with help of home testing kits that give quick results when you test your nasal swab. 
  • Alternatively, you may visit your healthcare provider and ask for a reverse transcriptase-polymerase chain reaction (RT-PCR) test (gold standard to diagnose COVID-19 and flu).

While the virus that causes COVID-19 and the flu viruses are thought to spread in similar ways (droplet infection by coughing and touching contaminated surfaces), the COVID-19 virus is more contagious compared to flu viruses and can evade the existing immunity much faster.

As of present, the COVID-19 virus seems to cause more serious illnesses in some people, such as:

The delta variant of COVID-19 illness has been known to cause severe respiratory illness and increased mortality even in young, healthy individuals.

Additionally, the COVID-19 infection can cause serious complications that include blood clots in the veins and arteries of the lungs, heart, legs, or brain, as well as a multisystem inflammatory syndrome in children (MIS-C) and adults (MIS-A). These are COVID-19-specific complications not observed in flu.

Long COVID-19 is an umbrella term for a range of symptoms that can last weeks or months after first being infected specifically with the COVID-19 virus.

Is flu vaccine necessary?

In the present scenario, it is essential to take the flu and COVID-19 vaccines (with booster) as directed by your healthcare practitioner.

Everyone aged six months and older should get influenza (flu) vaccine every season unless there have specific conditions that make it dangerous for them to receive vaccines.

Though influenza (flu) is not as serious as COVID-19 in most people, it can be potentially serious in the elderly, kids, and those with a weak immune system.

Vaccination has been shown to have many benefits, including reducing the risk of flu illnesses, hospitalizations, and flu-related death in children and the elderly.

All flu vaccines in the United States are “quadrivalent” vaccines, which means they protect against four different flu viruses: an influenza A (H1N1) virus, an influenza A (H3N2) virus, and two influenza B viruses.

You can take the vaccine listed in the table that is best suited for you after discussing it with your doctor.

Vaccine type Vaccine brand name Route of administration Indications
Quadrivalent cell-based influenza shot Flucelvax quadrivalent Injectable 6 months and older
Recombinant quadrivalent influenza shot Flublok quadrivalent Injectable 18 years and older
Quadrivalent flu shot using an adjuvant Fluad quadrivalent Injectable 65 years and older (elicit a stronger immune response)
Quadrivalent high-dose influenza vaccine Fluzone high-dose Injectable 65 years and older (contain a higher dose of antigen for better immune response)
Live attenuated influenza vaccine FluMist quadrivalent Injectable 2 to 49 years (contraindicated for pregnant and immunocompromised persons)

The following individuals should not take the flu vaccines:

  • Severe reaction to a previous flu shot
  • History of Guillain–Barre syndrome with any previous vaccination
  • History of egg allergy (only some type of flu vaccine contraindicated)

The intranasal flu vaccine is not recommended in the following populations:

  • Pregnant women
  • Immunocompromised individuals (human immunodeficiency virus-positive, immunosuppressant medications, cancer patients)
  • Those with cochlear implants
  • 50 years and older
  • Those who have cerebrospinal fluid leaks due to head surgery, trauma, or preexisting condition
  • Severe allergy to any component of the vaccine
  • 2 to 17 years old individuals on aspirin and other medications containing salicylates
  • Those who have recently taken antiviral drugs

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Medically Reviewed on 1/19/2022
References
Image Source: iStock Images

Centers for Disease Control and Prevention. Key Facts About Seasonal Flu Vaccine. https://www.cdc.gov/flu/prevent/keyfacts.htm