The flu (influenza) is a respiratory illness that can cause mild to severe illness that can result in hospitalization or death. The two main types of flu (influenza) virus, types A and B, are responsible for seasonal flu epidemics each year.
How Long Does the Flu Last?
Symptoms of the flu usually come on suddenly and can last several weeks.
Flu symptoms tend to occur in three stages and include the following:
- Days 1 through 3
- By day 4
- Cough, some mild chest discomfort, and hoarse, dry, or sore throat become more noticeable
- Fatigue
- Fever and muscle aches decrease
- By day 8
- Symptoms decrease
- Cough and tiredness may persist for one to two weeks or longer
What Tests Are Used to Diagnose the Flu?
The flu (influenza) is diagnosed based upon the patient’s symptoms and a physical examination.
Tests used to diagnose the flu include:
- Rapid molecular assays
- Rapid influenza diagnostic tests (RIDTs)
- Other specialized flu tests may be used in hospitals or state public health laboratories
What Is the Treatment for the Flu?
The flu (influenza) is treated with home remedies and antiviral medicines in some cases.
Home remedies to help relieve symptoms of the flu include:
- Rest
- Drinking plenty of fluids
- Saline nasal spray or drops
- Clean humidifier or cool mist vaporizer
- Inhaling steam from a bowl of hot water or shower
- Sucking on lozenges
- Do not give lozenges to young children because they pose a choking hazard
- Over-the-counter (OTC) medicines for relief of symptoms
- Pain relievers and fever reducers
- Acetaminophen (Tylenol)
- Ibuprofen (Advil, Motrin)
- Aspirin
- Do not give aspirin to children because it can cause Reye’s syndrome, a rare but serious illness
- Cough and cold medicines
- Pain relievers and fever reducers
Antiviral medications may be used to treat the flu. Antivirals for the flu work best when taken within 48 hours of the onset of symptoms to help reduce the severity and duration of the illness.
Antiviral medications used to treat the flu include:
- Oseltamivir phosphate (Tamiflu)
- Zanamivir (Relenza)
- Peramivir (Rapivab)
- Baloxavir marboxil (Xofluza)
Does the Flu Vaccine Prevent the Flu?
The Centers for Disease Control (CDC) recommends everyone 6 months and older get an annual flu vaccine as the best way to prevent the flu (influenza).
While a flu shot is not 100% effective in preventing the flu, it can reduce the severity and duration of flu illnesses, doctors’ visits, and missed work and school due to the flu, as well as prevent flu-related hospitalizations and deaths.
From 
https://www.cdc.gov/flu/index.htm
https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/flu-influenza