January 11, 2022
4 min. read

Flu: Influenza Symptoms, Diagnosis, and Treatment


What is influenza?

Influenza is a viral infection that affects your respiratory system—the nose, and throat, and sometimes the lungs. While it’s commonly referred to as “the flu,” it’s different from stomach flu viruses that can cause diarrhea and vomiting.

In most cases, those who get the flu will recover on their own, but it can also cause serious illness. While the annual flu vaccine isn’t 100% effective, it is the best way to prevent the flu and serious complications.

flu symptoms

What are some signs and symptoms of influenza?

Symptoms of the flu usually come on suddenly and can include:

  • Fever
  • Aching muscles
  • Chills and sweats
  • Headache
  • Dry, persistent cough
  • Shortness of breath
  • Tiredness and weakness
  • Runny or stuffy nose
  • Sore throat
  • Eye pain
  • Vomiting and diarrhea, more common in children than adults

How is influenza diagnosed?

Most people who get the flu will be able to treat themselves at home and, in most cases, won’t need to see a doctor. But if you do visit a provider for your flu symptoms, they will conduct a physical exam, check out your signs and symptoms, and, if necessary, order a test that can detect the influenza virus.

If you visit your doctor during a time when the influenza virus is widespread, you will likely be diagnosed based on your signs and symptoms alone. But if your doctor suggests that you be tested for the virus, there are a number of tests that can detect flu viruses. The most common is the rapid influenza diagnostic test, or RIDT. RIDTs work by detecting the parts of the virus that stimulate an immune response.

While these tests can provide results within ten to fifteen minutes, they are also generally not as accurate as other types of flu tests. Another, more accurate type of test is the rapid molecular assay, which detects genetic material of the flu virus. This test can produce results in fifteen to twenty minutes. A third type of test is called a polymerase chain reaction (PCR) test. This is one of the more accurate tests for detecting the flu, but will usually take one to several hours to get results.

flu treatment

How is influenza treated?

Typically, rest and fluids are enough to help you recover from the flu. However, if you are suffering from a severe infection, or are at a high risk of complications, your doctor may prescribe you an influenza antiviral medication. These prescription medications can be taken in pill form, as liquids, inhaled powders, or intravenously, and work to fight against flu viruses in your body. If you feel as though your infection is especially bad or if you are considered high risk, it’s best to consult with a doctor to determine a recovery protocol.

Antiviral drugs work best when taken soon after your flu symptoms begin. If taken within two days of becoming sick, antivirals can lessen fever and flu symptoms and shorten the time you feel sick by about one day. They may also reduce the risk of complications such as ear infections in children, respiratory complications requiring antibiotics, and hospitalization in adults.

This season, there are four FDA-approved antiviral drugs recommended by CDC to treat flu this season:

  • oseltamivir phosphate
  • zanamivir
  • peramivir
  • baloxavir marboxil

Antiviral medications can cause nausea and vomiting, but these side effects may be lessened if the drug is taken with food.

Is influenza different from a cold?

Influenza and the common cold are both contagious respiratory illnesses, but they are not the same—they are caused by different viruses. Influenza is caused by influenza viruses only, whereas the common cold can be caused by a number of different viruses.

flu v cold

But because the flu shares many symptoms with the common cold, it can be easy to confuse the two. In general, flu symptoms are generally worse than cold symptoms, can be more intense and usually begin more abruptly. Colds are usually much more mild, and are much more likely to cause a runny or stuffy nose. While colds do not normally cause serious health problems, the flu can be much more dangerous, especially for those with health complications.

Sources: 1. Influenza (flu) – Symptoms and causes. (2021, November 1). Mayo Clinic. 2. Key Facts About Influenza (Flu) | CDC. (2021, August 26). Centers for Disease Control and Prevention. 3. PCR Test for COVID-19: What It Is, How Its Done, What The Results Mean. (2021, August 24). Cleveland Clinic. 4. Diagnosing Flu | CDC. (2021, September 14). Centers for Disease Control and Prevention. 5. What You Should Know about Flu Antiviral Drugs. (2021, August 31). Centers for Disease Control and Prevention. 6. Liu J, Lin S, Wang L, Chiu H, Lee J. Comparison of Antiviral Agents for Seasonal Influenza Outcomes in Healthy Adults and Children: A Systematic Review and Network Meta-analysis. JAMA Netw Open. 2021;4(8):e2119151. doi:10.1001/jamanetworkopen.2021.19151

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