Flu Stages: A Day-by-Day Guide

Flu stages follow a relatively predictable timeline. Symptoms tend to develop one to two days after exposure to the influenza virus and last five to seven days. Older people or people with weakened immune systems may take longer to recover, while young, healthy people may take longer for symptoms to develop.

Understanding the stages of the flu—including the signs and symptoms that are likely to develop—can help you determine if you are recovering as you should. It can also help you figure out if you are still contagious and able to infect others.

Flu Day 0

Day 0 is the stage when you get the virus.

Infection occurs when a person with flu coughs, sneezes, or talks, propelling tiny droplets into the air that are breathed into your mouth or nose. It is also possible to get flu by touching contaminated surfaces and then your nose, eyes, or mouth.

At this stage, you will feel fine and be entirely unaware that you are about to get sick within the next day or two.

Even so, you are technically contagious on Day 0. The amount of virus in the mucosal tissues of the upper respiratory tract may not yet be at transmittable levels, but that can change with each passing hour as the virus starts to rapidly multiply in your nasal passages and throat.

Flu Day 1

Day 1 is when the body mounts an aggressive immune defense.

It does so by releasing proteins called antibodies that coordinate the immune attack and trigger inflammation. Inflammation helps neutralize the virus but also causes uncomfortable symptoms like heat, swelling, and pain.

At the start of Day 1, you may wake up feeling fine but progressively feel worse as the day goes on. By the end of the day, you may start developing the tell-tale early signs of flu, including:

• Headache
• Sudden high fever
• Body aches
• Chills

Flu Day 2

Day 2 is when flu symptoms have fully taken hold, extending from the upper respiratory tract—including the nostrils, nasal cavity, mouth, pharynx (throat), and larynx (voice box)—to the trachea (windpipe).

On this day, you may not be able to get out of bed and will start to experience the classic array of flu symptoms, such as:

• High fever with chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue

Flu Day 3

Day 3 is often described as the worst stage of the flu. This is the day when many symptoms are at their most intense.

Inflammation of the nasal passages and pharynx can cause severe congestion and sore throat. Persistent high fever can make it difficult to even lift your head.

The inflammation spreading from the trachea to the bronchi (the main airways of the lungs) will cause an intense, generally dry (non-productive) cough at this stage.

In small children especially, vomiting or diarrhea can occur.

Flu Day 4

Day 4 is generally the turning point in the infection. At this stage, the immune system will have gained control over the virus. You may start to feel a little better but probably too weak to do anything but sleep.

Your fever will likely have broken, and you shouldn't have as many body aches. Any congestion should start to loosen as well.

Even so, the aftermath of the infection can manifest with other symptoms.

The massive inflammation in the trachea and bronchi can cause the overproduction of mucus that begins to clog the lungs. When this happens, the dry cough may become more chesty and wet (productive) and get worse rather than better.

Even if your fever has broken, it is important to stay in bed and get plenty of fluids. By the end of the day, you may start to feel worse again and your fever may return.

Flu Day 5

Day 5 is the stage where active recovery begins.

While the infection itself will be mostly clear, there may still be some underlying inflammation, which is perfectly normal. This is because inflammation not only defends the body against infection but also starts the healing process by increasing blood flow to injured tissues.

At this stage, your fever should be gone. You should also have less congestion but will still likely have a cough. You may even find yourself coughing up phlegm (sputum) or becoming hoarse from all of the coughing.

If you are not starting to feel better by Day 5 or find that your symptoms are getting worse, call your healthcare provider.

Flu Day 6

Day 6 is when you should be well enough to get out of bed. There may still be some residual coughing, but breathing will be easier and the fever should be entirely gone.

While you may feel well enough to go back to work, the CDC advises against this until you have been fever-free for at least 24 hours without taking any fever-reducing medications.

People with the flu may be contagious anywhere from one day before to seven days after the appearance of flu symptoms.

Flu Day 7

Day 7 is the stage when most people can confidently go out into public.

Even so, you should continue to take standard precautions to protect others around you. Cover your mouth while coughing and sneeze into a tissue or the crook of your elbow. Wash your hands immediately after, and disinfect any surfaces with a general-purpose cleaner.

With that said, Day 6 or 7 is the time when certain people start to develop acute bronchitis (inflammation of the bronchi). This may be caused when the lingering virus moves into the lungs. Less commonly, it is caused by a secondary infection in which bacteria enter airways that have been weakened by the flu.

While most cases of acute bronchitis are relatively mild, they can cause a lingering wet cough that persists for weeks. Severe cases should be seen by a healthcare provider.

Other people have been known to develop otitis media (a middle ear infection) after the flu, also typically mild.

Flu Day 8

Day 8 is typically the "all-clear" day for most people, including children. Most people should be well on their way to recovery and will likely no longer be contagious.

Even most older adults should be fine by this stage, though it may take them longer to fully recover. Don't be distressed if you feel out of sorts and have a lingering cough for another week. This is not uncommon.

If you are used to exercising regularly, you should be fine to work out again—just don't go overboard. Your body is still recovering and can tire easily.

Cold and Flu Healthcare Provider Discussion Guide

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When to See a Healthcare Provider

Most people recover from the flu at home with conservative treatment. Unless you are at risk for complications or experiencing severe symptoms, it is important to rest and to avoid transmitting the virus to others.

People who are at risk for complications should consult their healthcare provider as soon as they start to experience flu symptoms. You may be at risk for complications if:

• You are over the age of 50.
• You have a chronic health condition such as diabetes, kidney disease, or heart disease.
• You have a chronic respiratory condition such as asthma or chronic obstructive pulmonary disease.
• You are in the second or third trimester of pregnancy.
• You have a weakened immune system.

Children between the ages of 6 months and 2 years are also at higher risk for complications.

If you or your child has the flu, watch out for signs of severe illness. If any of these symptoms appear, see a healthcare provider right away:

• Difficulty breathing
• A severe cough that produces thick yellow or green mucus
• A severe sore throat
• Faintness
  

Summary

Flu symptoms tend to develop one to two days after exposure to the virus and last for five to seven days. Day 1 to day 3 is characterized by the abrupt onset and worsening of symptoms. Day 5 to day 6 is when most people start to feel notably better.

By day 8, most people will have recovered and no longer be contagious. However, some may still have a lingering cough and fatigue.