Each year, about 5-20% of the United States population gets infected with the influenza virus, and more than 200,000 people are sent to the hospital for flu-related illnesses and complications.
Epidemics of the seasonal flu occur each year in the United States.


This is commonly known as “flu season,” which begins in the fall and typically reaches its peak in January or February, but can be seen as early as October and run through May. Flu activity can vary from region to region, and may peak at different times of the year across the country.

While typically a mild infection, the flu can become a serious illness, particularly for the elderly, newborns, and those with certain chronic illnesses. Most patients no longer experience symptoms after one to two weeks, but can pass the infection on to others up to 24 hours prior to the onset of symptoms, or as late as up to 5-7 days after symptoms appear.

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What is the Flu?

The flu, also known as influenza or grippe, is a contagious viral infection of the respiratory system, which includes the nose, throat, and lungs. The majority of cases of the flu result in mild illness, although can progress to severe illness and even death.

In the majority of patients, the flu subsides on its own or in combination with rest, hydration, and possibly a few over the counter medications. Children are up to three times more likely than adults to get the flu, and frequently spread the virus to others.

The influenza virus can be detected via a flu test, such as the “rapid influenza diagnostic test.” Depending on the type of test used, and the type or strain of flu virus the patient has, a negative influenza test may result, despite a patient presenting with flu-like symptoms. In fact, most people with flu symptoms do not undergo testing, and are often diagnosed based on their symptoms and their medical provider’s clinical judgement.

What Causes the Flu?

The flu is caused by the influenza virus. The two most common types of influenza virus are Influenza A and Influenza B. Influenza A can be broken down into different sub-types, depending on the genes present on the viral surface proteins. Flu illnesses from Influenza A strains typically cause more severe illnesses than those from Influenza B strains. Influenza C strains typically cause only mild respiratory illnesses, and are not responsible for flu epidemics or outbreaks. A patient can have the flu more than one time, as there are different strains and families of the influenza virus, each of which can produce a new infection and illness.


Medical experts agree that the flu spreads through contact with an infected person, directly or indirectly. When a person with the flu coughs, sneezes, or talks, contagious droplets containing influenza germs are spread. These droplets pass through the air, can be inhaled, and then land in the nose or mouth of another person and can spread the flu. The influenza virus can also be spread by touching a surface or object that contains the flu virus, and then touching your eyes, mouth, or nose.

Signs and Symptoms of the Flu

Flu symptoms typically subside after 3-7 days, but lingering coughs and fatigue may last for an additional two weeks or more.

Common flu symptoms include:


Flu symptoms often come on suddenly, present quickly, and are typically worse than the common cold. Colds are not often accompanied by fever or headaches, while the flu rarely causes an upset stomach. Although many people often describe feelings of nausea, vomiting, and diarrhea as the “stomach flu,” these symptoms can be caused by a variety of viruses, bacteria, or parasites, and are rarely symptoms of the influenza virus or “seasonal flu,” and are often only seen in young children with the flu. It’s important to keep in mind that the flu is a respiratory virus, and not a stomach infection or intestinal disease.

Prevention of the Flu

Medical professionals and the CDC (The Centers for Disease Control and Prevention) agree that the single most effective way to prevent the flu is to get vaccinated. The CDC recommends that everyone 6 months and older get vaccinated every year, as soon as the flu vaccine becomes available. This is typically in October, and is the first and most important step to flu prevention. Because it takes about 2 weeks after vaccination for a healthy adult to produce antibodies against the flu virus, it is important to take the time to get vaccinated as early as possible.

It is not possible to catch the flu from the flu vaccine, and the risk of harm from the flu shot is extremely small. Flu vaccines are developed with either flu viruses that have been inactivated, or without any flu virus at all (recombinant vaccines), and therefore are not infectious. Although you may feel soreness in your arm, aches, or have a low fever, these symptoms would be much worse if you had actually contracted the flu virus.

The typical flu vaccine contains protection against three different strains of the influenza virus, and is known as a Trivalent flu vaccine. This form protects against two different types of Influenza A (currently H1N1 and H3N2), and an Influenza B virus. Quadrivalent flu vaccines protect against four different strains – two Influenza A and two Influenza B strains. Various forms of the flu vaccine have been developed, to suit the needs of those in different age groups, health status, and those with allergies – such as an egg allergy. Most people experience little or no reaction to the flu shot, and may encounter muscle soreness at the site of injection.

If any of the following pertain to you, it is recommended that you speak with your medical provider prior to obtaining a flu vaccine:

  • Have had an allergic reaction to a previous flu shot

  • Have an allergy to eggs

  • Have previously developed Guillain-Barré Syndrome within 6 weeks of getting a flu shot in the past

  • Are 6 months of age or younger

  • Currently have an illness with a fever (it is recommended that you wait until your current symptoms have subsided before getting a flu shot)


As an alternative to an injection, a new vaccination option that has recently been approved by the FDA for healthy, non-pregnant, patients ages 2-49. This new alternative is called FluMist, and is a nasal spray vaccine. Those who are healthy but work with, or are in close contact with, those with very weakened immune systems should refrain from getting the FluMist nasal spray, as it contains live, yet weakened forms of the flu virus. This population of people should instead get the flu shot, which is an inactivated form of the vaccine. Others who should consult with a medical provider prior to getting the FluMist nasal spray flu vaccine include those who:

  • Are younger than 2 years of age

  • Are 50 years of age or older

  • Suffering from weakened immune systems

  • Have from long-term health problems

  • Include children or adolescents currently on long-term aspirin therapy

  • Have diabetes, kidney disease, heart disease, or lung disease

  • Have a history of Guillain-Barré Syndrome

  • Are pregnant

  • Have had an allergic reaction to a previous flu vaccine

  • Have an allergy to eggs

In addition to vaccination, it is advisable to avoid contact with sick individuals to prevent spread of contagious virus particles. Frequent hand washing, with soap and warm water, can help reduce the spreading of germs. If soap is not available, an alcohol-based hand rub can be an effective substitution. Those who are sick should not share linens, eating utensils, and dishes until these items have been thoroughly washed. When coughing and sneezing, it is advisable to do so into a tissue or the inner crook of your elbow, to avoid spread of the flu virus. If infected, to avoid further spreading the flu, the CDC recommends that patients remain at home for at least 24 hours after fever or other symptoms have subsided.

To promote a healthy lifestyle and increase immune function, it is also important to maintain a balanced diet, get regular exercise, get adequate sleep each night, and manage daily or life stresses. These will help reduce your chance of catching and suffering from the flu.


Treatment of the Flu

Often, the flu can be treated simply with plenty of rest and drinking lots of fluids. Fluids such as water, juice, and warm soup can help prevent dehydration.

Over the counter medications can help soothe symptoms related to the flu. Acetaminophen (Tylenol) or ibuprofen (Advil, Motrin IB) are pain relievers that can help fight off the body aches commonly seen with the flu. Phenylephrine (Sudafed PE) and pseudoephedrine (Sudafed 12 hour) are oral decongestants available for nasal congestion relief, along with nasal decongestant sprays.

Complementary health alternatives are also available, though evidence of their efficacy is not conclusive. Some people take oral zinc or vitamin C supplements to reduce the duration and severity of flu symptoms.

A medical provider can also prescribe antiviral medications, such as zanamivir (Relenza) or oseltamivir (Tamiflu), and rimantadine (Flumadine). Antiviral drugs are only available via prescription, and help fight against the influenza virus. It has been shown that antiviral drugs can lessen the severity and duration of symptoms by 1-2 days, and can help prevent serious complications such as pneumonia from arising. Studies have supported the efficacy of antiviral drugs when taken within 2 days of becoming sick. The CDC supports antiviral use for patients including those who have high risk conditions, including children, and those who are pregnant.


Zanamivir is an inhaled medication (often in powder form), and can be used through a device similar to an asthma inhaler, while oseltamivir is an oral medication (as a pill or in liquid form.) Your medical provider can discuss with you which medication is best for you. Some common side effects and adverse reactions of these antiviral medications include:

  • Nausea

  • Vomiting

  • Dizziness

  • Runny or stuffy nose

  • Cough

  • Diarrhea

  • Headache

  • Delirium or self-harm (has been associated with teenagers using oseltamivir)

  • Reparatory complications in patients with respiratory problems, including asthma and lung disease (when taking zanamivir)

  • Viral resistance to these medications, thus ineffectiveness against the influenza virus


When Should I Call a Doctor?

While everyone is at risk for the flu, many people find that rest and hydration are sufficient and no further medical help is necessary. If your symptoms persist, worsen, or you would like to speak with a medical provider for further medical advice or assistance, contact your primary care physician or request a telehealth consultation.

Patients who have a greater risk of serious complications from the flu should consult a medical provider immediately. With proper medical care and possible antiviral medication, flu symptoms and severity will likely decrease. Antiviral medication taken within the first 48 hours of illness can offset further complications. Patients at higher risk for serious flu-related complications include those who are:

  • Under the age of 5, particularly those younger than 2 years old

  • Older than the age of 65

  • Pregnant

  • Very obese, with a body mass index (BMI) of 40 or more

  • Living in a nursing home or long-term care facility

  • Suffering from weakened immune systems (patients suffering from HIV or AIDS, patients being treated with steroids or chemotherapy, cancer patients)

  • Suffering from chronic illness – such as asthma, emphysema, chronic bronchitis, bronchiectasis, chronic obstructive pulmonary disease, cystic fibrosis, heart disease, chronic kidney disease, diabetes, anemia, liver disorders

  • Suffering from neurological or neurodevelopmental conditions

  • Younger than 19 years of age and on long-term aspirin therapy

  • Of American Indian or Alaskan Native descent

  • Asthmatic

  • Suffering from blood disorders, such as sickle cell disease


On average, 200,000 patients in the United States get hospitalized each year due to flu-related complications, such as:


Emergency warning signs that warrant assessment by a medical provider include:

  • Rapid or difficulty breathing

  • Chest or abdominal pain

  • Rapid dizziness

  • Sudden confusion

  • Inability to keep liquids down

  • Severe and/or persistent vomiting

  • Improvement of flu-like symptoms with sudden onset and worsening of fever and cough

  • Blue-colored skin

  • Fever with a rash

  • Infants and children with an inability to eat

  • Lack of tears in crying infants

  • Significant reduction in number of soiled wet diapers in infants

This page offers general health information to facilitate discussion with your telehealth provider. You must not rely on the information on our website as an alternative to medical advice from your doctor or other professional healthcare provider.

If this is a medical emergency, please call 911. For mental health emergencies, call 988.

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