Influenza: Seasonal Flu 2013-2014
Symptoms, Treatment, and Prevention



This course will expire or be updated on or before December 1, 2014.

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Influenza: Seasonal Flu 2013–2014
Symptoms, Treatment, and Prevention

By Neil S. Davis, RN, PHN

Neil Davis worked for over a decade as an emergency department nurse. He obtained national certifications in both critical care and emergency nursing. He moved into a leadership role acting as nurse manager for a small Northern California ICU. He then assumed the role of director of nurses for a mid-sized group of community health clinics. During his time working in the acute care setting, he volunteered on a wide variety of community health promotion and community development projects focusing on promoting physical activity. He now works independently on community health initiatives with a variety of nonprofit agencies.

Persis Mary Hamilton, RN, CNS, MS, EdD

Persis Hamilton has a rich background in nursing, nursing education, and writing. She has written 14 nursing textbooks for 2 major publishers. She works with Wild Iris Medical Education to ensure compliance with ANCC accreditation guidelines. Persis taught for more than 40 years in vocational, associate, baccalaureate, and graduate nursing programs, served as item writer for the League for Nursing, and was the principle speaker at numerous CE workshops. She has also conducted research in Micronesia and Guam. Currently, Persis maintains a private practice in psychotherapy and recently completed a historical novel about the care of psychiatric patients in the 1930's, entitled Deportation Train.

COURSE OBJECTIVE:  The purpose of this course is to provide up-to-date information about the symptoms, treatment, and prevention of seasonal flu.


Upon completion of this course, you will be able to:

  • Discuss key concepts related to the transmission, symptoms, diagnosis, and treatment of flu.
  • Explain the rationale for vaccination and other preventative measures against seasonal flu.


Influenza is an ancient and deadly disease, first described by Hippocrates more than 2,400 years ago. Since then, the disease has sickened and killed millions of people in local epidemics and global pandemics. The most lethal pandemic of record began in 1918, just after World War I, when 40 to 100 million people died from what was called the Spanish flu.

In 1931, Richard Schope discovered the cause of influenza (the Orthomyxoviridae family of viruses) in pigs; and in 1944, Thomas Francis Jr. developed the first significant steps toward preventing the disease with an inactivated-virus vaccine. His work was made practical by Frank MacFarlane Burnet, who showed that the virus lost virulence when it was cultured in fertilized hens’ eggs. This allowed researchers at the University of Michigan to develop the first influenza vaccine. Since then, vaccination has limited its spread but has not prevented pandemics of the disease (Potter, 2001).

In 1957, the Asian flu swept around the world, killing 1 to 1.5 million people, and in 1968, a pandemic called Hong Kong flu killed nearly a million more. Then, in 2009, a pandemic called swine flu, caused by virus found in pigs, swept around the world. As a consequence, a vaccine against the three causative viruses was developed. However, because viruses change constantly, each year WHO publishes vaccine recommendations to prevent what is now called seasonal influenza (CDC, 2013a; WHO, 2010).

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All influenza viruses belong to the Orthomyxoviridae family of RNA virus, including types A, B, C, Isa virus, thogotovirus, and others. Each type contains two surface glycoprotein antigens, called subtypes—hemagglutinin (HA) and neuraminidase (NA). The HA antigen enables the virus to enter cells, while the NA antigen facilitates cell-to-cell transmission. These subtypes are further differentiated by their numbered surface antigens, serotypes 1 to 10.


Type A viruses are the most virulent of influenza types, producing the most severe symptoms. They infect humans, other mammals, and birds and are the cause of all known pandemics, including:

  • H1N1: Spanish flu of 1918 and pandemic threat of 2009
  • H2N2: Asian flu of 1957
  • H3N2: Hong Kong flu of 1968
  • H5N1: pandemic threat of 2008

Type B viruses have only one serotype and infect humans and seals.

Type C viruses have but one serotype, infect humans and pigs, and are relatively uncommon.

Isa virus viruses infect fish and cause infectious anemia in salmon.

Thogotovirus viruses are found in ticks, mosquitoes, and mammals; human epidemics from them are unknown.

Additional types of influenza viruses are being discovered, but to date, type A and B are known to pose the greatest threat to human health.


A number of human cases of “swine flu” (H3N2v) have been reported in the United States beginning in August 2011. This virus normally occurs in pigs but does not usually infect people. Evidence from the 2011 and 2012 flu seasons suggests the strain produces mild symptoms and is judged to pose a relatively low risk of pandemic. Although the virus can be spread from human to human, it is primarily a zoonotic transmission (from animal to human). Most cases were contracted at fairs after exposure to pigs, and the CDC therefore recommends that children who are at high risk should avoid fairs where they may be exposed to pigs.

Early steps to make a vaccine against H3N2 have been taken, but there is no plan to mass-produce the vaccine at this time. (Seasonal vaccine is not designed to protect against H3N2v.) Public health authorities are watching this situation closely. They advise those who are in contact with pigs to take normal precautions such as washing hands frequently with soap and running water before and after exposure to animals and avoiding drinking, eating, or putting things in one’s mouth while in animal areas.

Source: CDC, 2013b.

Immune Response and Influenza Vaccines

When viruses laden with antigens enter a human or an animal, the body recognizes them as foreign substances and reacts in what is called an immune response. This response creates antibodies against the foreign substance even when that substance is an inactivated influenza virus. Later on, if humans or animals are infected with active virus, the antibodies that were created earlier protect them against the virus, reducing the severity of symptoms (Michael et al., 2009).

Due to their immature immune response systems, children 6 months to 8 years old who are receiving an influenza vaccine for the first time require an additional dose. An optimal immune response will be initiated by administering a second dose a minimum of 4 weeks after the first dose (CDC, 2013c; Ygberg & Nilsson, 2012).

Late in life, our immune systems become less responsive. In response to this, a high-dose trivalent influenza vaccine has been developed for those 65 and over and for those with compromised immune systems (CDC, 2013o).

Antigen Drift and Shift

Influenza viruses change constantly. They do this in two ways: antigenic drift and antigenic shift.

Antigenic drift is caused by an accumulation of the many small mutations that are continually occurring in both influenza A and B viruses. These mutations occur within both HA and NA genes. When this happens, antibodies may only partially recognize the resultant viruses or may not recognize them at all. Thus, when an antigen drift occurs, the current vaccine may not provide protection against disease. This is the reason why influenza vaccines must be updated annually.

Antigenic shift is an abrupt, major change in the influenza viruses, resulting in new HA and/or NA proteins. As a result, a new vaccine must be made to combat the altered virus. For this reason, people must be vaccinated anew to be protected from the altered virus of seasonal influenza (CDC, 2013d).

Small, incremental build up of changes Large, sudden change
Expected, researchers alert to potential Unexpected and unpredictable
Less likely to lead to pandemic More likely to lead to pandemic
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The most common way influenza viruses spread from person to person is by droplet infection. Infected people exhale, cough, or sneeze, and virus-containing droplets fly through the air into the nose and throat of others or onto some intermediate surface such as a doorknob. When other people touch a contaminated surface, viruses may stick to their fingers. When they touch the mucus membranes of their body, they inoculate themselves with the virus.

To prevent the spread of disease, individuals are instructed to:

  • Cover their nose and mouth with tissue when coughing or sneezing; discard tissue in the trash
  • Wash their hands often with soap and water or alcohol-based hand rub
  • Avoid touching their eyes, nose, and mouth
  • Try to avoid close contact with sick people
  • If sick with flu-like illness, stay at home for at least 24 hours after their fever is gone, except for medical care or for other necessities
  • While sick, limit contact with others as much as possible to keep from infecting them
  • Take flu antiviral drugs if their doctor prescribes them
    (CDC, 2013e)

There is no research definitively demonstrating that the use of masks by either the patient or caregiver reduces the transmission of influenza. However, the CDC recommends offering masks to patients who arrive in a healthcare setting as part of a respiratory hygiene/cough etiquette strategy (CDC, 2013f).

According to the CDC, sick adults are able to infect others beginning 1 day before symptoms appear and up to 5 days after they become ill. Sick children may be able to infect others beginning 1 day before symptoms appear and for more than 7 days after they become ill.

Symptoms develop 1 to 4 days after the virus enters the body. That means people may be able to pass on the flu virus to others even before they know they are sick. Any individual who is infected with viruses can infect others whether they show symptoms or not. Some infected persons are contagious for up to 10 days (e.g., infants and immunosuppressed and immunocompromised persons) (CDC, 2013g).


John Smith, a 57-year-old man with a history of asthma, had been experiencing flu-like symptoms for three days. He was running a fever and, despite using his inhaler more frequently, was increasingly short of breath. At the urging of his wife, he went to the emergency department (ED) to be checked. On arrival, the front office staff noticed that he was frequently coughing and responded per their policy by offering him a facemask to wear while he waited in the waiting room. A few minutes later he was brought into triage, where the nurse confirmed that his symptoms were consistent with a contagious phase of influenza. During triage, the nurse allowed him to remove his facemask for his comfort but donned a facemask herself to minimize the risk that she might transmit the virus to her family or other patients who had not yet been vaccinated.

During his workup, the ED team continued the practice established by the triage nurse of wearing facemasks when they were within three feet of the patient while allowing him the comfort of not wearing a facemask. He was admitted to the hospital with a diagnosis of left lower lobe pneumonia. On the advice of the infection control nurse and in accord with CDC recommendations, he was presumed to be infectious and was asked to wear a facemask when out of his room or being transported, while healthcare workers and visitors donned facemasks when they expected to come within three feet of him.

The infection control nurse explained to John and his family that, although there is no definitive evidence that facemasks decrease the spread of the influenza virus, the CDC still recommends the use of facemasks as a prudent measure to decrease the spread of the virus.

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Anyone can be infected with the flu virus, but the disease is more severe and the consequences more critical for some people than others. The most vulnerable are children under 5 years of age, especially those younger than 2 years of age; adults 65 years of age and older; pregnant women; and American Indians and Alaskan Natives (CDC, 2013h).

In addition, influenza can make chronic health problems worse. For example, individuals with asthma may suffer asthma attacks and people with chronic congestive heart failure may experience an accumulation of fluid in the lungs, abdominal organs, and peripheral tissue. Generally speaking, people with the following medical conditions are more vulnerable to serious influenza-related complications:

  • Asthma
  • Neurological and neurodevelopmental conditions, including disorders of the brain, spinal cord, peripheral nerve, and muscles
  • Chronic lung diseases such as chronic obstructive pulmonary disease and cystic fibrosis
  • Heart diseases such as congestive heart failure, congenital heart disease, and coronary artery disease
  • Blood disorders such as sickle cell disease
  • Endocrine disorders such as diabetes
  • Metabolic disorders such as inherited metabolic and mitochondrial disorders
  • Weakened immune system due to disease or medication (such as HIV or AIDS, or those on chronic steroids)
  • Kidney disorders
  • Liver disorders
  • Morbid obesity (body mass index >40)
  • Any condition in children younger than 19 years of age that requires long-term aspirin therapy
    (CDC, 2013h)
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Symptoms and Severity

Influenza is a highly contagious infection of the respiratory tract. It can cause mild to severe illness and may lead to death. The incubation period is brief and the onset sudden, causing chills, fever, aching muscles, and general malaise. Symptoms include:

  • Fever (usually high, however, not everyone with flu has a fever)
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headache
  • Fatigue
  • Vomiting and diarrhea (in some people; more common in children than adults)
    (CDC, 2013g)

The indicators of influenza are referred to as “flu-like symptoms.” In the early stages of an infection, it may be difficult to distinguish between a common cold and influenza. However, the symptoms of flu are more severe and last longer than the common cold. A comparison of the usual symptoms of seasonal influenza and the common cold are listed below.

Symptom Influenza Common Cold
Sources: CDC, 2013i; Perry, 2010.
Onset Brief, may be less than 24 hours after exposure Gradual, over several hours or days
Fever Usually higher than 100 ˚F (37.8 ˚C), however not everyone with flu develops a fever Rare in adults and older children; may rise to 102 ˚F in infants and young children
Headache Sudden onset, may be severe Rare
Muscle aches Usual, often severe Mild
Fatigue Often extreme, may last 2 weeks or more Never
Weakness Often extreme, may last 2 weeks or more; children may show low activity level Mild and, if present, of brief duration
Rhinitis and runny nose Common Common
Sneezing Common Common
Sore throat May occur Common
Nausea, vomiting, diarrhea May occur in adults; more common in children Never in adults
Cough Hacking; may be severe and last for weeks after infection Mild


Diagnosis of influenza is based on presenting symptoms and viral tests. However, most individuals with flu symptoms do not require special testing because test results usually do not change their treatment. Individuals who have an acute febrile respiratory illness, sepsis-like syndrome, or are members of vulnerable groups listed above (such as infants, the elderly, and those with compromised immune systems) should be tested. This is because they require more intense treatment such as antiviral medications. Priority for diagnostic testing includes persons who 1) are at high risk for severe disease and 2) require hospitalization.


There are two types of tests that detect influenza viruses: rapid influenza diagnostic tests (RIDT) and viral cultures (VC). Both tests require a mucus specimen collected from the back of the throat or nose by a healthcare provider (see “How to Obtain a Nasopharyngeal Specimen” below).

Rapid influenza diagnostic tests (RIDT) yield results in 15 minutes or less and display the results as “positive” or “negative.” However, these results are not foolproof and may give a false negative when the patient is actually infected or a false positive when the patient is not infected with influenza viruses.

Viral cultures (VC) of mucus specimens are more accurate than RIDT but are costly and time-consuming. Mucus specimens must be obtained by skillful healthcare providers, transported to hospital or state public health laboratories, grown under controlled conditions, and analyzed by expert technicians. All this takes time and expert execution (CDC, 2013j).


  • Ask patient to blow his or her nose just prior to specimen collection. Provide tissues and a place to dispose of the contaminated tissues. Then, ask patient to wash or sanitize his or her hands with alcohol wipes.
  • Explain the procedure to the patient in order to obtain his or her cooperation.
  • Gather equipment: appropriate swab, transport media, and personal protective equipment (PPE), including gloves, gown, respiratory, and eye protection as prescribed by public health officials. Ideally, use a swab with a synthetic tip such as polyester or Dacron and an aluminum or plastic shaft. (Swabs with cotton tips and wooden shafts are not recommended, and those made of calcium alginate are not acceptable.) Specimen collection vials should contain 1 to 3 ml of viral transport medium containing protein stabilizer, antibiotics to discourage bacterial and fungal growth, and buffer solution.
  • Wash or sanitize your hands and put on personal protective equipment.
  • Instruct patient to tilt his or her head back.
  • Insert the swab straight back into one nostril; stay against the nasal septum until resistance is felt.
  • Rotate the swab for 15 seconds. Instruct the patient to swallow and not to cough.
  • Remove the swab and immediately place it into the collection vial. Label the specimen and send it to the laboratory for processing.

Source: Baden et al., 2009.

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Comfort and Care

People young and old who are infected with the virulent viruses of flu are desperately ill. They sneeze and often have hacking coughs and runny noses. Their head and muscles ache, and they feel extreme fatigue. Nausea, vomiting, and diarrhea are common. Sick children and adults may crawl into a fetal position, shiver with chills and fever, and feel too sick to talk or even cry.

Such seriously ill people need rest, comfort, sleep, and extra fluids. They may benefit from analgesics and antipyretic medications such as ibuprofen (Advil) and acetaminophen (Tylenol). Aspirin should be avoided due to its anticoagulant effects and to avoid the development of Reye’s syndrome in children. Children younger than 18 years of age should not receive salicylates such as acetylsalicylic acid or aspirin (Stoppler, 2011; Porat & Dinarello, 2012). In spite of the misery for the first few days, most children and adults gradually recover in one to two weeks without complications or antiviral medications.

Antiviral Medications

Antiviral medications can shorten the duration of fever and illness, reduce the risk of complications from influenza, and shorten duration of hospitalization. The CDC (2013k, 2013l) recommends these drugs be given as early as possible to individuals who exhibit more critical symptoms and suffer from chronic conditions or influenza-related complications such as:

  • Hospitalized patients with confirmed or suspected influenza
  • Individuals who are younger than 19 years of age who are receiving long-term aspirin therapy
  • People who are at higher risk for complications, including:
    • Children younger than 2 years of age
    • Adults 65 years and older
    • Women who are pregnant or postpartum within 2 weeks of delivery
    • People with certain chronic medical conditions
    • People with immunosuppression caused by medications, HIV, or other disorders
    • American Indians/Alaska Natives
    • Persons who are morbidly obese (body mass index >40)

The American Academy of Pediatrics (AAP) recommends antiviral drugs for children who are at high risk of flu-related complications and have moderate to severe cases of influenza. They cite a significant benefit in giving antiviral drugs to children ages 1 to 12 years because such treatment reduces the incidence of ear infections and the resultant need for antibiotics (AAP, 2007).

Drugs recommended by both CDC and AAP to fight type A and B influenza are:

  • Oseltamivir (Tamiflu): Available as a liquid or capsule, oseltamivir is approved both to prevent and treat flu in people 1 year of age and older. The most common side effects are nausea and vomiting. The Food and Drug Administration requires that the package warn that people with the flu, especially children, may be at an increased risk of confusion and self-injury after taking the drug. Therefore, recipients should be monitored closely for signs of unusual behavior.
  • Zanamivir (Relenza): Available only as a powder, zanamivir is administered to the respiratory tract via an oral disk inhaler device. It is approved to treat flu in people 7 years of age and older and to prevent flu in those 5 years of age and older. The most common side effects are diarrhea, nausea, sinusitis, bronchitis, cough, headache, dizziness, and ear, nose, and throat infections. People with chronic lung disease such as asthma have reported serious breathing problems after taking the drug.

Both antiviral drugs work best when started within 2 days of the onset of symptoms (without waiting for laboratory confirmation of the disease) and continued for at least 5 days. Hospitalized patients may benefit from treatment even if the drug is started more than 48 hours after symptoms begin and treatment is continued for a minimum of 5 days (CDC, 2013l; AAP, 2007).

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Because influenza produces such serious symptoms, the CDC issues prevention recommendations to the public.


  1. Take time to get flu vaccinations.
  2. Take everyday preventative actions:
    • When coughing or sneezing, cover the nose and mouth with the arm or with a tissue, then discard tissues in the trash.
    • Wash hands often with soap and water or use alcohol-based rub.
    • Avoid touching the eyes, nose, and mouth.
    • Stay at home for at least 24 hours after the fever is gone except to get medical care or necessities.
    • When it is necessary to go out, limit contact with others, especially avoiding nasopharyngeal droplets from infected individuals.
  3. Take flu antiviral drugs if recommended by a doctor.

Source: CDC, 2013a.

Routine cleaning and disinfection strategies can also help prevent the spread of influenza. Management of laundry, utensils, and medical waste should be performed in accordance with established procedures.

Who Should Be Vaccinated?

Everyone 6 months of age and older should get vaccinated against the flu except a few select individuals (see below). Vaccination is especially important for vulnerable individuals with chronic medical conditions, healthcare workers, and others who live with or care for high-risk people. Those who care for children younger than 6 months should also be vaccinated (CDC, 2013a).

Those who should not be vaccinated before talking to their doctor include:

  • Those who have had a severe reaction to an influenza vaccination in the past (pain, swelling, and redness at the site of injection are not considered severe; any other symptoms should be reported to a physician prior to administration)
  • Persons with moderate to severe acute febrile illness until symptoms are relieved
  • Those who developed Guillain-Barré syndrome within 6 weeks of getting an influenza vaccine previously

In the past, people with egg allergies were unable to receive the vaccine. However, a new “egg-free” vaccine is now available in limited quantities for those with severe egg allergies. Those with mild egg allergies can be vaccinated but should not receive a live attenuated vaccine. For patients with mild or severe egg allergies the vaccine should only be administered in settings with emergency equipment and a physician with experience in managing anaphylaxis present. CDC guidelines should be carefully reviewed on a case-by-case basis with a physician before administering a vaccine to a person with a history of egg allergy (CDC, 2013p).

Vaccines for the 2013–14 Influenza Season

Influenza vaccines are updated annually to provide a combination of the most likely strains to be in circulation. Trivalent vaccine formulations contain three viruses—typically two type A viruses and one type B virus. Quadrivalent vaccines contain four viruses—typically two type A and two type B viruses.

The 2013–2014 trivalent influenza vaccine is made from the following three viruses:

  • A/California/7/2009 (H1N1) pdm09-like virus
  • A(H3N2) virus antigenically like the cell-propagated prototype virus NA/Victoria/361/2011
  • B/Massachusetts/2/2012-like virus

This year’s quadrivalent vaccine contains the above tree strains plus a B/Brisbane/60/2008-like virus.

While the H1N1 and H3N2 viruses in this year’s formulations are the same as the 2012–2013 recommendation, the recommended influenza B vaccine virus is different from those recommended for the Northern Hemisphere for the 2011–2012 influenza vaccine (CDC, 2013m).


The U.S. Food and Drug Administration licenses two types of seasonal influenza vaccine for use in the United States:

  • Flu shot: an inactivated vaccine (containing killed virus of the three identified viral strains), given with a needle, usually in the arm. The flu shot is approved for use in people older than 6 months, including healthy people, pregnant women, and people with chronic medical conditions. Three preparations of inactivated vaccine are available:
    • Regular flu shots approved for people ages 6 months and older
    • High-dose flu shots approved for people age 65 and older
    • Intradermal flu shot approved for people ages 18 to 64
  • Nasal spray: live but weakened flu viruses of the three identified viral strains, which do not cause the flu. Sometimes this type of vaccine is called live attenuated influenza vaccine (LAIV). LAIV is approved for use in healthy individuals 2 to 49 years of age who are not pregnant (CDC, 2013n).

The increasing number of vaccination dosing and route options is leading to improved targeting and specificity in delivering influenza immunization while also allowing more people to be vaccinated than ever before. However, the variety of options is beyond what providers can commit to memory, particularly considering the frequency with which the options are updated.

Nurses who expect to be providing influenza vaccines should familiarize themselves with the CDC references and obtain copies of the most current dosing and administration tables so, in consultation with medical providers, they are prepared to quickly ascertain the best vaccine options for their patients while maintaining the five rights of medication administration. (See “Resources” at the end of this course.)


On a Friday in early September, Maria Jones, RN, was asked by a patient when she should receive her annual flu shot and if she could have the nasal spray so she didn’t need to have “a shot.” Maria was embarrassed because she was unprepared to answer the question. She told her patient she wasn’t sure but thought it was still a little early and reassured her she would look into it and give her a call with further information.

Over the weekend, Maria went to the Centers for Disease Control website and read about seasonal influenza vaccinations. She found a table that showed dosing and route information as well as information regarding when vaccinations should be provided. She printed the table and presented it to her nurse and physician coworkers when she came to work Monday morning. Together, they practiced using the tables to determine the best option for a variety of their patients.

With a confirmation from the physician, Maria was then able to call her patient and tell her the CDC recommends that vaccines be given as soon as they are available and that they expected to have their first doses available in early October. Unfortunately, she had to inform her patient she was outside the age recommendations for the nasal spray and would need to get a shot.

Public Education

Prevention of epidemics and pandemics depends on education of the public about the importance of vaccination and personal hygiene. The more vaccinated individuals, the fewer cases of influenza. The greater use of personal hygiene by individuals, such as covering a sneeze or cleansing the hands, the less likely viruses will infect other people. For these reasons, healthcare providers have a special responsibility to encourage the general public to be vaccinated and to practice protective sanitary measures.


Influenza continues to be a deadly disease, but due to the work of scientists and clinicians, people can be protected from infection by the ever-changing influenza viruses. With vaccination against the viruses and protective sanitary measures, infections can be reduced; and with antiviral medications, vulnerable individuals and those who are infected can be treated. Healthcare providers play an important role in delivering this message to those they serve.

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Centers for Disease Control and Prevention (CDC)
Seasonal flu:
Immunization recommendations:

U.S. Department of Health and Human Services (DHHS)

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American Academy of Pediatrics (AAP), Committee on Infectious Diseases. (2007). Antiviral therapy and prophylaxis for influenza in children. Pediatrics, 119(4), 852–960. Retrieved from

Baden LR, Drazen JM, Kritek PA, Curfman GD, Morrissey S, & Campion EW. (2009). H1N1 influenza a disease—information for professionals. New England Journal of Medicine, 360(25), 2666–7.

Centers for Disease Control and Prevention (CDC). (2013a). Key facts about seasonal flu vaccine. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013b). Protect yourself against H3N2v. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013c). Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP)—United States, 2012–13 influenza season. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013d). How the flu virus can change: “drift” and “shift.” Retrieved from

Centers for Disease Control and Prevention (CDC). (2013e). CDC says “Take 3” actions to fight the flu. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013f). Interim guidance for the use of masks to control influenza transmission. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013g). Clinical signs and symptoms of influenza: influenza prevention & control recommendations. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013h). People at high risk of developing flu-related complications. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013i). Flu symptoms and severity. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013j). Use of antivirals. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013k). “Have you heard?” CDC recommendations for influenza antiviral medications remain unchanged. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013l). Children and antiviral drugs. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013m) What you should know for the 2013–2014 influenza season. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013n). Summary recommendations: prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP)—United States, 2013–14. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013o). Fluzone high-dose seasonal influenza vaccine. Retrieved from

Centers for Disease Control and Prevention (CDC). (2013p). Influenza vaccination: a summary for clinicians. Retrieved from

Michael M, et al. (2009). Influenza vaccination with a live attenuated vaccine. American Journal of Nursing, 109, 44–8.

Perry M. (2010). Differentiating between the common cold and influenza. Practice Nurse, 40(10), 11–5.

Porat R & Dinarello CA. (2012). Up To Date. Pathophysiology and treatment of fever in adults. Retrieved from

Potter CW. (2001). A history of influenza. Journal of Applied Microbiology, 91, 572–9. Retrieved from

Stoppler MC. (2011). Medicine.Net: Reye’s syndrome. Retrieved from

World Health Organization (WHO). (2010). WHO recommendations for the post-pandemic period. Retrieved from

Ygberg S & Nilsson A. (2012). The developing immune system—from foetus to toddler. Acta Paediatrica, 101(2), 120–7.

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