Influenza: Symptoms, Diagnosis, and Treatment

The word “flu” is often used very casually. People say they had the flu, or the stomach flu, or “some kind of flu is going around.” Actual influenza usually makes people sick enough that it is clearly something different.

If you did not get the influenza vaccine as flu season begins and you get sick, how will you know it is the flu? Most people who actually have it know that they have something more than the common cold.

Symptoms of influenza

Symptoms of influenza usually come on suddenly, and can include:

  • Headache
  • Muscle pain
  • Backache and aching joints
  • Eye pain – pain when moving the eyes – this is often a sign that you have influenza
  • Fever (between 100.4 degrees to 105.8 degrees)
  • Chills
  • Some respiratory symptoms like sore throat, cough, and runny nose
  • Nausea, vomiting and diarrhea – this is more common in children

These symptoms are frequently severe. While the worst part is at the beginning, people frequently feel sick for a week to ten days, and are also often extremely fatigued and weak afterwards with a lingering cough.

Different strains of influenza may cause slightly different prominent symptoms. During the 2009 to 2010 season, more people had vomiting and diarrhea than with other flu. In general, the flu that year caused less severe symptoms in most people.

While most people have a high fever with the flu, not everyone does. The elderly may not have a high fever.

If you are not improving, or your fever goes down after you have been sick for a few days and then goes up again, you may be developing a complication of influenza. You need to see a doctor if this happens.

Diagnosis of influenza

If you come down with symptoms of influenza during flu season, and you are a healthy young adult, you do not have to go to the doctor. You can treat your own symptoms.

If you go to the doctor during flu season, the doctor will examine you but may not need to run any tests.

If it is not flu season, or if public health officials want doctors to document the flu strains in their area during flu season, they can take swabs from your throat or nose for culture. Cultures give results in anywhere from 2 to 3 days to as long as 10 days, so they are not useful for deciding whether or not you need medication specifically for the flu.

There are rapid tests that can be done in a doctor’s office or lab that can have results in as little as 15 minutes of processing time. They can tell influenza A from B, which can help doctors know which medications to give.

More tests or x-rays would only be done if you had symptoms pointing to something other than influenza, or a complication of influenza such as pneumonia.

General advice for treating influenza symptoms

Otherwise healthy children and adults usually recover from the flu without specific treatment. If you have the flu, you can take Tylenol® (acetaminophen) for the fever and pain. Sometimes Advil® (ibuprofen) or Aleve® (naproxen) may give more relief. There are over-the-counter medications for stuffy nose and cough that can be helpful.

Anything that lowers temperature makes a person with influenza much more comfortable. If you have the flu, you may have chills as your temperature rises and want to cover up. That actually makes you feel worse. If you have the flu you should be loosely covered.

Fluids need to be taken in, even if you are vomiting. The higher the fever and the more diarrhea and vomiting, the greater the risk of dehydration. Small frequent sips of fluid will often stay down. Pedialyte® for children and something like Gatorade® for adults is better than plain water, fruit juice or soda. Imodium® can be taken for diarrhea.

You will need time to regain your strength, as well as time for your body to completely fight off the illness. You should not try and rush back to work. Not only will you not be able to work effectively if you are not really well, but you can also pass the flu to your coworkers.

It is recommended that you stay at home for 24 hours after you have no fever without the use of Tylenol or other medications used to lower temperature. At this point you will probably not be contagious and may feel well enough to work.

There are specific treatments for influenza. Antiviral medicine requires a trip to the doctor. There is also treatment for the complications of influenza like pneumonia.

If you have any chronic medical problems and you think you have influenza you should call your doctor as soon as possible to get antiviral treatment. But the best thing is to get vaccinated so you do not get influenza. If you do experience this viral illness, you will probably want the vaccine before the next flu season starts.

Specific treatment for influenza

There are antiviral medicines that can treat most strains of influenza. The CDC (Centers for Disease Control) and other government agencies check the flu viruses circulating each year to help make recommendations about which antiviral drug will work best. As is the case with bacteria and antibiotics, influenza virus can develop resistance to antivirals.

These medications are the most effective when taken during the first 48 hours of the illness. They may be used later on if someone is extremely sick with influenza. They can also be used to help prevent influenza in someone who has been exposed. An exposed individual who has a medical problem making them more likely to have complications from influenza can be given a combination of the vaccine and antivirals for two weeks. After 2 weeks, their own immunity should kick in.

Older antivirals like amantadine no longer work against most influenza. The two most commonly used drugs are Tamiflu® (oseltamivir) and Relenza® (zanamivir). Tamiflu® can be taken in pill or liquid form for children. Relenza® comes as a powder that is inhaled; it cannot be used by people with breathing problems like asthma or COPD (emphysema). Either of these medications can be used to treat both influenza A and B.

Oseltamivir is taken twice a day. The dose for children at least one-year old depends on their actual age and weight. Adults take 75 mg twice a day, usually for 5 days. It may given for a longer period of time to people so sick that they are in the hospital.

When oseltamivir is used to prevent influenza, the dose also varies by age and weight; adults take 75 mg once a day for one to two weeks depending on the type of exposure. The most common side effects are nausea and vomiting. There have been episodes of psychiatric problems reported in specific groups of people; this is a very rare side effect.

Zanamivir is not approved for children treatment of influenza in children less than 7 years of age. Everyone else who can take this inhaled medicine get two inhalations twice a day. It can be given to prevent influenza in people 5 years of age or older who are exposed; the dose is 2 inhalations once a day. Zanamivir can cause swelling of the mouth and face plus other symptoms such as congestion, cough, headache and dizziness, all considered ear, nose and throat side effects. It can also cause nausea and diarrhea.

During flu season, the CDC will inform medical professionals as to the sensitivity of the viruses to these agents. They will also monitor to see which groups of people are being affected the most by the flu and who therefore need antiviral treatment. This essentially always includes the very old and very young, as well as people with chronic medical problems.

Each flu season is slightly different. The 2009-2010 swine flu caused more problems for pregnant women than other influenza strains. During the 2009-2010 flu season, medications were authorized for use in younger children, as well as by different routes, for those who were seriously ill.

Updates are issued frequently during flu season and recommendations may change depending on the sensitivity of the circulating influenza as well as the severity of the disease. There was even an investigational drug authorized for use in hospitalized patients who were critically ill with the swine flu. In 2009, for example, peramivir was given to patients in the hospital with flu resistant to oseltamivir, and zanamivir was given by vein.

If you did not get a flu vaccination and believe you are coming down with influenza during flu season, you can call your doctor to get advice about antiviral treatment. This is especially important if you have chronic medical problems, are 65 years of age or older, are being given any medication that affects your immune system. It is also important that parents of young children talk to their pediatrician if they suspect flu.

Complications of influenza like pneumonia may be treated with antibiotics. People who are very sick are treated in the hospital. Antibiotics do nothing to improve symptoms of influenza itself.

The very best thing is to make sure you get vaccinated and are not going to get influenza, or if you catch it, your symptoms will be much less severe. Sign up at the website below to get a notification when it is time to get the vaccine.

Get vaccinated.

References Seasonal Flu.

CDC: Seasonal influenza. Information for Health Professionals

Prevention and Control of Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. MMWR 2011; 60(33):1128-1132.

Harrison’s Practice: Answers on Demand. Kasper, Braunwald, Fauci, Hauser, Longo, Jameson (eds). Copyright © The McGraw-Hill Companies, Inc.

The Merck Manual for Health Care Professionals. Respiratory Viruses. Influenza. Last full review/revision October 2009 by Ronald B. Turner, MD. Content last modified October 2009.

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Dr. Anna Kaplan

Dr. Anna Kaplan graduated with a BA in English literature from Pomona College in 1975. She received her MD from U.S.C. School of Medicine in 1979. A three-year residency (training period) in family practice followed, and she was certified by the American Board of Family Physicians in 1982. She recertified, a normal procedure, in 1988 and 1995. She retired from active practice after 15 years, but keeps up with medicine via continuing medical education.

Dr. Kaplan has written in the medical field for both consumers as well as professionals. She has also authored hundreds of articles on other subjects.

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