Influenza (Flu) | Infectious Diseases

Infectious Diseases

Influenza (Flu)

You deserve expert care, even for common illnesses like influenza (the flu). Our team is easy to reach and delivers treatments that speed healing.

Medically reviewed by Dean Blumberg, M.D. on Aug. 18, 2023.

Woman blowing her nose in bed.

What Is the Flu?

The flu is a viral infection that is highly contagious and typically strikes in the fall and winter. There are two main types. Influenza A is more common and can cause severe symptoms. Type B is rarer and more likely late in the season, like February and March. 

At UC Davis Health, you receive prompt influenza care close to home. Many primary care provider locations offer same- and next-day appointments for flu symptoms. 

Our telehealth express care service makes it possible to receive some services from home. You may still need to come to a lab for testing to confirm the diagnosis. 


Flu Symptoms

The influenza virus affects your nose and throat. Occasionally, it impacts your lungs. In some people, it causes discomfort lasting a few days. Sometimes flu symptoms make people very sick, requiring immediate care in the hospital.

Common Flu Symptoms

The symptoms you experience depend on where the infection spreads and its severity.

  • Cough
  • Diarrhea
  • Fever and chills
  • Head- and body aches
  • Sore throat
  • Tiredness
  • Vomiting

Emergency Influenza Symptoms

Severe symptoms or ones that do not improve in a few days require prompt medical attention.

  • Chest pain and difficulty breathing
  • Dehydration from frequent vomiting or diarrhea
  • Lightheadedness
  • Skin or lips turning blue

Causes and Risk Factors of the Flu

Influenza happens when you get infected with the flu virus. After exposure, it may take a few days for you to start feeling sick. 

There are some risk factors that can slightly increase your chances of getting influenza.


Young children and older adults are more likely to develop severe flu that may require hospital care.

Other Medical Issues

You face a higher risk if you have a weakened immune system or ongoing medical issues like diabetes.

Vaccination Status

If you have not received your annual flu shot, you have little natural defense against it.


Diagnosis and Testing for Flu

If you have flu-like symptoms, seeing a provider promptly is essential. We can confirm the diagnosis and flu type using a quick lab test. This information helps you start treatments, like antiviral medications, earlier when they’re more likely to be effective.

Flu Treatments

The treatment that’s best for you depends on the flu type and severity.

Antiviral Medications

These medications fight the flu virus, helping you recover in less time. Antiviral drugs also lower the likelihood of flu-related complications.

Home Remedies

Rest is essential when you are trying to recover from the flu. It is also important to get a lot of fluids so you don’t get dehydrated.

Symptom Relievers

Additional medications can improve specific symptoms. Saline nasal spray reduces sinus pressure, making it easier to breathe. Ibuprofen helps treat body aches.

Professional Guidance

Your provider will give you information about flu-related complications and what to do if you think you have one. Additional treatments may be necessary if you have a high fever that doesn’t go away, chest pain or faintness.


Preventing the Flu

While influenza can be highly contagious, taking certain precautions significantly lowers your risk of infection.


One of the best ways to prevent the flu is by getting an annual flu shot.


You can also avoid contact with people who are sick. If you must share space with an infected person, regularly wash your hands and disinfect high-touch surfaces like doorknobs.

Face Masks

Respirator masks such as N95s can prevent you from inhaling the influenza virus. A well-fitted face mask can provide an extra layer of protection in crowded public areas like airports.

"Assessment of a respiratory face mask for capturing air pollutants and pathogens including human influenza and rhinoviruses," Journal of Thoracic Disease, 

Average number of hospitalizations

200K+Each year in the U.S.

Flu shot impact

40-60%Less likely to need to go to the doctor if you get the shot

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