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Influenza: Seasonal Flu 2017-2018
Symptoms, Treatment, Prevention

Online Continuing Education Course

Course Description

Flu CE course covering the transmission, symptoms, diagnosis, and treatment of influenza during the 2017-2018 season. Distinguish flu versus cold. Discuss current flu vaccination recommendations of the CDC (injectable only). Applicable for nursing, occupational therapy, physical therapy, and EMS personnel.

Course Price: $18.00

Contact Hours: 2

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Influenza: Seasonal Flu 2017–2018
Symptoms, Treatment, and Prevention

LEARNING OUTCOME AND OBJECTIVES:  Upon completion of this course, you will be able to demonstrate an understanding of the symptoms, treatment, and prevention of seasonal influenza for 2017–18. Learning objectives for this course include:

  • Discuss key concepts related to the transmission, symptoms, diagnosis, and treatment of influenza (flu).
  • Explain the rationale for vaccination and other preventative measures against seasonal flu, based on the chain of infection.

Influenza (flu) is a highly contagious respiratory illness that has sickened and killed millions of people in local epidemics and global pandemics. Caused by different types of influenza viruses, it can bring about mild to severe illness, sometimes leading to hospitalization or death. Those at high risk for serious complications include older adults, young children, and people with certain health conditions. An annual vaccination is the best way to prevent the flu. The composition of flu vaccines in the United States is reviewed and updated annually to protect against the types of flu virus that researchers believe will be most common that year.


The first documented pandemic that clearly fits the description of influenza was in 1580. The most lethal pandemic of record began in 1918, just after World War I, when an estimated 21 million people died from what was called the Spanish flu (CDC, 2016a).

Smith, Andrewes, and Laidlaw isolated influenza A virus in ferrets in 1933, and Francis isolated influenza B virus in 1936. In 1936, Burnet showed that the virus lost virulence when it was cultured in fertilized hens’ eggs. This led to the study of the characteristics of the virus and the development of inactivated vaccines. The protective efficacy of these inactivated vaccines was determined in the 1950s.

Since then, vaccination has limited the infection’s spread but has not prevented pandemics of the disease (CDC, 2016a). 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 (CDC, 2016b). Then, in 2009, a pandemic called swine flu, caused by a virus found in pigs, swept around the world, causing an estimated 575,000 deaths (WHO, 2017).


All influenza viruses belong to the Orthomyxoviridae family of RNA viruses, including types A, B, C, Isa virus, thogotovirus, and others.

Types of Influenza Viruses

There are four types of influenza viruses: A, B, C, and D. The human influenza viruses A and B cause the seasonal epidemics of disease almost every winter in the United States. When a new and very different influenza A virus emerges, it can cause an influenza pandemic.

Type A viruses are found in humans and many different animals, including ducks, chickens, pigs, whales, horses, seals, and cats. Type A viruses are the most virulent of influenza types, producing the most severe symptoms. Influenza A types contain two surface glycoprotein antigens, called subtypes hemagglutinin (H) and neuraminidase (N). The H antigen enables the virus to enter cells, while the N antigen facilitates cell-to-cell transmission. There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes (H1 through H18 and N1 through N11, respectively).

Type A viruses that infect humans can be further broken down into different strains. Current subtypes of influenza A viruses are influenza A (H1N1) and influenza A (H3N2) viruses.

In 2009, a new influenza A (H1N1) virus emerged that was very different from the human influenza A (H1N1) viruses that were circulating at that time. This new virus caused the first influenza pandemic in more than 40 years. That particular virus has now replaced the earlier H1N1 subtype that was circulating previously in humans (CDC, 2017a).

Type B viruses infect only humans, generally cause milder disease than type A, and primarily affect children. Type B is more stable (less able to mix or swap genetic material with other viruses) than influenza A and consequently has immunologic stability. They are not divided into subtypes but can be broken down into lineages and strains. Currently influenza B viruses belong to one of two lineages:

  • B/Yamagata
  • B/Victoria

Type C viruses have one serotype, infect humans and pigs, and are relatively uncommon. Influenza type C is rarely reported as a cause of human illness, probably because most cases are mild and present no obvious symptoms. It has not been associated with epidemic disease.

Type D influenza viruses affect cattle primarily and are not known to infect or cause illness in people (CDC, 2016c).

Immune Response

When viruses laden with antigens infect 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 and is referred to as active immunity. After recovery from the infection, the human or animal is usually immune to getting the same viral disease for years (perhaps a lifetime). Influenza vaccines help develop immunity over a few to several weeks by imitating an infection and causing the immune response that protects against the virus in the future.

Passive immunity occurs when a person is given antibodies to a disease rather than producing them through the immune system. Passive immunity can be obtained by receiving antibody-containing blood products such as immune globulin when immediate protection is required. Such protection lasts only for a few weeks or months (CDC, 2017b).

Antigen Drift and Shift

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

Antigenic drift is a natural mutation over time of known strains of influenza, which may lead to a loss of immunity or vaccine mismatch. This natural mutation is caused by a slow accumulation of many small mutations that happen in all types of influenza, including influenza virus A, B, and C. These mutations occur within both hemagglutinin (H) and neuraminidase (N) 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 process by which at least two different strains of a virus (or different viruses) combine to form a new subtype having a mixture of the surface antigens of the two original strains. Antigenic shift occurs only in influenza A viruses because it infects more than just humans. As a result, a new vaccine must be made to combat the altered virus, and people must be vaccinated anew to be protected from the altered virus of seasonal influenza (IVN, 2017).

  • Small, incremental build-up of changes
  • Expected, researchers alert to potential
  • Less likely to lead to pandemic
  • Large, sudden change
  • Unexpected and unpredictable
  • More likely to lead to pandemic

Examples of influenza viruses with pandemic potential include avian influenza A H5, A H7, and A H9. These are nonhuman viruses (i.e., they are novel among humans and circulate in birds in parts of the world), so there is little to no immunity against these viruses among people. Human infections with these viruses have occurred rarely, but if either of these viruses were to change in such a way that it was able to infect humans easily and spread easily from person to person, an influenza pandemic could result.

Although avian influenza A viruses usually do not infect humans, rare cases of human infection with these viruses have been reported. Most human infections with avian influenza A viruses have occurred following direct or close contact with infected poultry.

  • Avian A H5 influenza viruses have occurred in 16 countries, with a 60% mortality worldwide due to severe pneumonia.
  • Avian A H7 influenza high pathogenic subtypes viruses have caused mild to severe illness, but in 2013 a new subtype was reported in China causing severe respiratory illness and death.
  • Avian A H9 influenza viruses cause sporadic infections resulting in mild upper respiratory illness.

The spread of avian influenza A viruses from one ill person to another has been reported very rarely. However, because of the possibility that avian influenza A viruses could change and gain the ability to spread easily between people, monitoring for human infection and person-to-person transmission is extremely important for public health.

Seasonal influenza vaccination will not prevent infection with avian influenza A viruses but can reduce the risk of infection with both human and avian influenza A viruses. It is also possible to make a vaccine that can protect people against avian influenza viruses. For example, the United States government maintains a stockpile of vaccine adequate to immunize 20 million persons against avian influenza A H5N1.

Source: CDC, 2017c; Cioce, 2013.

Seasonal Vaccine

Because viruses change constantly, the World Health Organization (WHO) monitors the changes globally each season. The data obtained is then used to predict the strain that will be most prevalent during the next flu season and to publish vaccine recommendations to prevent what is called seasonal influenza (WHO, 2016).

In 2016, a new strategy was developed that can predict flu mutations before they occur in nature by simulating the changes in a laboratory. This new laboratory-based method of predicting how current viral strains of influenza will mutate can also be used to help select the strains to be included in the next seasonal flu vaccine (NIAID, 2016a).

Three types of vaccine-induced antibodies have been identified that can neutralize diverse strains of influenza virus that affect humans. This discovery will help in the development of a universal influenza vaccine. Such a vaccine would be effective against multiple subtypes of influenza and would eliminate the need to update the vaccine each year. Dozens of vaccines are undergoing study around the world, and more than half of them are in the preclinical phase of study. As yet, it is uncertain when any of them will be ready for use (NIAID, 2016b).


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 mucous membranes of their body, they inoculate themselves with the virus.

Influenza viruses can survive on hard surfaces for 24 hours and can also survive for several hours as droplets in the air. Low temperatures increase their airborne survival (NHS, 2015).

Sick adults are able to infect others beginning one day before symptoms appear and up to five to seven days after they become ill. Sick children may be able to infect others beginning one day before symptoms appear and for more than seven days after they become ill.

Symptoms develop one to four 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 (NYSDH, 2016).


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 women up to two weeks postpartum
  • Residents of nursing homes and other long-term care facilities
  • Native Americans and Alaska Natives
    (CDC, 2016d)

Native Americans and Alaska Natives are more likely to be hospitalized from the flu than the general U.S. population. Experts are not sure exactly why, but reasons that these populations are at high risk of flu complications could include social and economic factors that often result in reduced access to healthcare and crowded living conditions (CDC, 2015).

In addition, influenza can make chronic health problems worse. For example, individuals with asthma may suffer asthmatic 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 (HIV, AIDS, cancer, steroids)
  • Kidney disorders
  • Liver disorders
  • Inherited metabolic disorders and mitochondrial disorders
  • Morbid obesity (body mass index ≥40) (found to be a risk factor, independent from other chronic illnesses, resulting in greater hospitalization and death during the H1N1 pandemic)
  • Any condition in children younger than 19 years of age that requires long-term aspirin therapy (related to Reye’s syndrome, see below)
    (CDC, 2016d)


Symptoms and Severity

Influenza is a highly contagious infection of the respiratory tract. The signs and symptoms of influenza can vary by age, immune status, and presence of underlying medical conditions. It should not be confused with a gastrointestinal illness sometimes referred to as the stomach flu. Uncomplicated influenza can cause mild to severe illness and may include any or all of these signs and symptoms:

  • Fever (usually high, however, not everyone with the flu has a fever, especially elderly persons)
  • Dry cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headache
  • Fatigue
  • Conjunctivitis, rhinitis, and gastrointestinal symptoms (more common in infants and young children than adults)
    (CDC, 2016e; Brook, 2016)

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 influenza and the common cold are listed below.

SYMPTOM Influenza Common Cold
Source: WDHS, 2016.
Fever Characteristic, high (100 °F–102 °F), lasts three to four days Rare
Headache Sudden onset, may be severe Rare, usually mild
Muscle aches Usual, often severe Mild
Fatigue Often extreme, may last 2 to 3 weeks Quite mild
Chills In about 50% of cases Not common
Rhinitis and runny nose Sometimes Common
Sneezing Sometimes Common
Sore throat May occur Common
Nausea, vomiting, diarrhea Not usual; most often in children Unusual
Cough Dry cough (no phlegm) that may be severe; may last several weeks Common, generally mild to moderate, usually produces phlegm


The 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. The CDC offers a guide for practitioners in considering influenza virus diagnostic tests for individual patients when influenza viruses are circulating in the community.

Decision-making flowchart for considering flu virus diagnostic testing.

Source: CDC, 2016f.


There are a number of different tests used in diagnosing influenza. All of the following tests can be obtained from 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) for antigen detection 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. False negatives are more likely when influenza activity is high; during periods of low influenza activity, false positives may occur more often.

  • RIDTs can help with diagnostic and treatment decisions for patients in clinical settings, such as whether to prescribe antiviral medications. 
  • Due to the possibility of a false negative result and/or the fact that this test is less likely to detect type B influenza, the decision to withhold antiviral medications from a symptomatic patient should not be based solely on a negative RIDT test result.
  • Once the presence of influenza activity has been documented in a community or geographic area, a clinical diagnosis of influenza can be made for outpatients with signs and symptoms consistent with suspected influenza, especially during periods of peak influenza activity in the community.

RITDs are used to detect influenza virus as the cause of respiratory infections, and public health authorities should be notified promptly of any suspected outbreaks, especially in institutions such as nursing homes, hospitals, schools, etc. Respiratory specimens should then be collected for ill persons and sent to a public health laboratory for more accurate influenza testing (CDC, 2017d).

Viral tissue cell culture of a mucus specimen is the “gold standard” for identifying which influenza viruses and which strains of virus are present. However, traditional viral cultures can take up to 10 days for results.

Rapid cell culture (shell vials, cell mixtures) yields live virus and takes one to three days.

Reverse transcription-polymerase chain reaction (RT-PCR) is a molecular assay that can identify the presence of influenza viral RNA or nucleic acid in respiratory secretions. It is used for hospitalized patients with suspected influenza and pneumonia if an upper respiratory tract specimen is negative and if positive testing would result in a change in clinical management. It is particularly useful in identifying influenza virus infection as a cause of respiratory outbreaks in institutions and in detecting novel influenza A strains. Results are generally available in one to six hours.

Immunofluorescence—direct (DFA) or indirect fluorescent-antibody (IFA) staining—is a type of antigen detection with results in one to four hours.

Rapid molecular assay is a diagnostic test for upper respiratory tract specimens and takes approximately 20 minutes (CDC, 2016g).

  • Explain the procedure to the patient in order to obtain his or her cooperation.
  • Ask the 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 the patient to wash or sanitize his or her hands with alcohol wipes.
  • 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 nylon. Specimen collection vials should contain 1 ml 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 PPE.
  • Tilt patient’s head back 70 degrees.
  • Insert swab into nostril. (Swab should reach depth equal to the distance from nostrils to outer opening of the ear.) Leave swab in place for several seconds to absorb secretions.
  • Slowly remove swab while rotating it. (Swab nostrils with same swab.)
  • Place tip of swab into sterile viral transport media tube and snap/cut off the applicator stick.

Proper technique for obtaining a nasopharyngeal specimen, with swab inserted to a depth equal to the distance from nostrils to outer opening of the ear. (Source: CDC, n.d.)


Comfort and Care

People young and old who are infected with the virulent viruses of influenza can be very ill. 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). 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.

Children and adolescents under 18 years of age who are experiencing influenza symptoms should not be given any medication containing salicylates, such as acetylsalicylic acid (aspirin), because it has been linked with the risk of Reye’s syndrome, a rare, but potentially fatal disease.

Measures should be taken to reduce the spread of infection, including handwashing, covering the mouth and nose when sneezing or coughing, and avoiding crowds during peak flu season. If sick, the person should stay home for at least 24 hours after fever subsides (Mayo Clinic, 2017).

Antiviral Medications

Antiviral medications can be used to treat or to prevent influenza following exposure in specific populations. They can shorten the duration of fever and illness, reduce the risk of complications from influenza, and shorten the duration of hospitalization. Antiviral medications are approximately 70% to 90% effective in preventing influenza. However, the CDC does not recommend widespread or routine use of antiviral medications for chemoprophylaxis so as to limit the possibilities that antiviral-resistant viruses could emerge (CDC, 2017e).


The CDC (2017e) recommends these drugs be given as early as possible to any patient who has confirmed or suspected influenza and:

  • Is hospitalized
  • Has severe, complicated, or progressive illness
  • Is at higher risk for influenza complications (as listed earlier in this course), including:
    • Children younger than 2 years of age
    • Adults 65 years and older
    • Women who are pregnant or postpartum within 2 weeks of delivery
    • Children and adolescents younger than 19 years who are receiving long-term aspirin therapy
    • People with certain chronic medical conditions, including chronic pulmonary, cardiovascular, renal, hepatic, hematological, and metabolic disorders, or neurologic and neurodevelopment conditions
    • People with immunosuppression, including those caused by medications or by HIV infection
    • Native Americans/Alaska Natives
    • Persons who are morbidly obese (body mass index ≥40)
    • Residents of nursing homes and other chronic care facilities

Although all children younger than 5 years are considered at higher risk for complications from influenza, the highest risk is for those younger than 2 years, with the highest hospitalization and death rates among infants younger than 6 months. Because many children with mild febrile respiratory illness might have other viral infections (e.g., respiratory syncytial virus), knowledge of other respiratory viruses as well as influenza virus strains circulating in the community is important for treatment decisions (CDC, 2017e).


Antiviral drugs approved by the U. S. Food and Drug Administration and recommended by the CDC for use during the 2017–2018 influenza season are:

  • Oral oseltamivir (Tamiflu): Oseltamivir is approved both to prevent flu following exposure (in people 3 months of age and older) and treat flu (in people of any age). The most common side effects are nausea and vomiting. Other side effects include serious skin/hypersensitivity reactions and neuropsychiatric events (self-injury or delirium, mainly reported among Japanese adolescents and adults); therefore, recipients should be monitored closely for signs of unusual behavior.
  • Inhaled zanamivir (Relenza): 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 for prevention in people 5 years of age and older. Allergic reactions include oropharyngeal or facial edema. Common side effects are diarrhea; nausea; sinusitis; nasal signs and symptoms; bronchitis; cough; headache; dizziness; and ear, nose, and throat infections. It is contraindicated for those with underlying respiratory disease such as asthma or COPD and for those with a history of allergy to milk protein.
  • Intravenous peramivir (Rapivab): Peramivir may be used for treatment in people 18 years of age and older. It is not recommended for chemoprophylaxis. Side effects could include diarrhea and serious skin reactions as well as sporadic transient neuropsychiatric events mainly among Japanese adolescents and adults.

Antiviral drugs work best when started within 48 hours of the onset of symptoms (without waiting for laboratory confirmation of the disease). Oseltamivir and zanamivir should be continued for at least five days. Recommendation for chemoprophylaxis is seven days from last known exposure. Duration of treatment with intravenous peramivir is one day. 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 five days (CDC, 2017e).


The Chain of Infection

The process of transmission of an infectious agent such as the influenza virus can be best explained by the epidemiologic model called the chain of infection. An infectious disease results from specific interactions between the organism, host, and environment. Transmission occurs when the infectious organism leaves the reservoir or host through a portal of exit, travels by some mode of transmission, and enters through a portal of entry to infect another susceptible host (APIC, 2017).

Diagram showing the links in the process of transmission of an infectious agent such as the flu virus.

Chain of infection. (Source: Wild Iris Medical Education.)

  • Infectious agent is the pathogenic organism that causes diseases.
  • A reservoir is the habitat where the infectious agent normally lives and grows. Reservoirs may be humans, animals, insects, or the environment.
  • The portal of exit is the path by which the infectious agent leaves its host (e.g., respiratory tract, open wounds).
  • Means of transmission is the mode in which the infectious agent is transmitted from its natural reservoir to a susceptible host (e.g., touching a doorknob that contains infectious particles or droplet spread). Transmission can occur in a mode that is direct or indirect.
  • The portal of entry refers to the way in which the infectious agent enters the host (e.g., through one’s nose into the respiratory tract when breathing in airborne particles, broken skin, mucous membranes, catheters, and tubes). The portal of entry must provide access to tissues in a way that allows the infectious agent to multiply and thrive.
  • The final link is the vulnerable or susceptible host. Susceptibility of a host depends on many factors, including immunity and the individual’s ability to resist infection
    (APIC, 2017).

By breaking any link of the chain of infection, healthcare professionals can prevent the occurrence of new infection. Infection prevention measures are designed to break the links and thereby prevent new infections. The chain of infection is the foundation of infection prevention.

Link Influenza Implications Healthcare Provider Actions
Infectious agent Present in environment during flu season Be aware of current strains and case reporting requirements
Reservoir Potentially everyone, some higher risk Promote vaccinations
Portal of exit Droplets Teach/reinforce sneeze/cough etiquette and correct use/disposal of tissues
Transmission Organism can remain active on environmental surfaces Teach disinfection techniques
Portal of entry Nose/mouth Teach/reinforce handwashing, not touching eyes/face, wearing masks
Vulnerable hosts Everyone; some people at greater risk Promote vaccinations among high-risk groups

Flu Prevention Measures

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:
    • Try to avoid close contact with sick people.
    • While sick with the flu, limit contact with others as much as possible to keep from infecting them.
    • When sick with flu-like illness, stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone for 24 hours without the use of a fever-reducing medicine.)
    • Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
    • Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
    • Avoid touching your eyes, nose, and mouth. Germs spread this way.
    • Clean and disinfect surfaces and objects that may be contaminated with germs like the flu.
  3. Take flu antiviral drugs if recommended by a primary care provider.
  4. If an outbreak of flu occurs in your area, follow the advice given by public health officials. Such information may include how to increase distance between people and other measures.
    (CDC, 2016h)

Although there is no proof that facemasks prevent transmission of the influenza virus, the CDC recommends the use of facemasks in the following situations:

  • Healthcare personnel should don a facemask when entering the room of a patient with suspected or confirmed influenza.
  • Patients with suspected influenza should be provided with a facemask when entering a healthcare facility.
  • Patients with flu symptoms should be instructed to wear a facemask when leaving home.
  • Patients under droplet precautions should wear a facemask when movement or transport outside of the room is necessary.

Mandating the use of facemasks for unvaccinated healthcare workers is not among the CDC’s recommendations and has aroused controversy.

Source: CDC, 2016i.

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.


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, found himself increasingly short of breath. At the urging of his wife, he went to the emergency department (ED) to be checked.

The ED intake staff noticed that Mr. Smith was frequently coughing, so they responded per facility policy by offering him a facemask to wear while he sat in the waiting room. As is consistent with their usual practice, the staff remembered to perform frequent hand hygiene. 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 Mr. Smith to remove his facemask for his comfort but donned a facemask herself to minimize the risk that she might become infected and transmit the virus to her family or other patients who had not yet been vaccinated. After sending the patient to the ED, the nurse remembered to clean all surfaces near the patient in the triage room, including the doorknobs, with an alcohol-based wipe prior to the next patient’s arrival.

During further diagnostic testing, 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.

Mr. Smith was admitted to the hospital with a diagnosis of left lower lobe pneumonia. On the advice of the infection prevention nurse, 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 prevention nurse explained to Mr. Smith and his family that, although there is no definitive evidence that facemasks decrease the spread of the influenza virus, it is still recommended to use facemasks as a prudent measure to decrease the spread of the virus.


Everyone 6 months of age and older should get vaccinated against the flu except for 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 be vaccinated (CDC, 2017f).

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 four weeks after the first dose. For children who require two doses of vaccine, the first dose should be administered as soon as the vaccine is available to ensure that both doses are received before the onset of influenza activity (Munoz, 2017).

Late in life, the immune system becomes less responsive. In answer to this, a high-dose trivalent seasonal influenza vaccine (Fluad) became available during the 2016–2017 flu season for those 65 years and over; it has been shown to induce significantly higher antibody responses and provide better protection against influenza illness (CDC, 2017f).


Those who should not be vaccinated before talking to their primary care provider include:

  • Those who have had a severe allergic reaction to an influenza vaccination in the past (e.g., anaphylaxis) after previous dose of influenza vaccine or to vaccine component
  • Persons with moderate to severe acute illness with or without fever until symptoms are relieved
  • Those who developed Guillain-Barré syndrome within six weeks of getting an influenza vaccine previously
    (CDC, 2017g)


The recommendations for people with egg allergies were updated for the 2016–2017 season and remain current for 2017–2018. Studies have shown that severe allergic reactions to the vaccine in people with egg allergies are unlikely, and a recent CDC study found the rate of anaphylaxis after all vaccines is 1.31 per one million vaccine doses given (CDC, 2016j).

  • People who have experienced only hives after exposure to egg can get any licensed flu vaccine that is otherwise appropriate for their age and health.
  • People who have symptoms other than hives after exposure to eggs (such as angioedema, respiratory distress, lightheadedness, or recurrent emesis) or who have needed epinephrine or any other emergency medical intervention also can get any licensed flu vaccine that is appropriate for their age and health, but the vaccine should be given in a medical setting and be supervised by a healthcare provider who is capable of recognizing and managing severe allergic conditions. Such settings include hospitals, clinics, health departments, and physician offices.
  • People with egg allergies no longer have to wait 30 minutes for observation after receiving their vaccine.
    (CDC, 2017g)


Following vaccination, some individuals experience mild side effects. These may include:

  • Soreness, redness, and swelling at the injection site
  • Hoarseness
  • Sore, red, or itchy eyes
  • Cough
  • Fainting, mainly in adolescents
  • Aches
  • Low-grade fever
  • Headache
  • Itching
  • Fatigue

Because these mild side effects mimic some influenza symptoms, some people believe the vaccine causes them to get influenza. But the injectable influenza vaccine produced in the United States has never been capable of causing influenza, because the only type of licensed vaccine licensed is made from inactivated influenza viruses, which cannot cause infection, or with no flu viruses at all, which is the case for the recombinant influenza vaccine.

More serious side effects may include a small increased risk of Guillain-Barré syndrome after inactivated flu vaccine. Risk is estimated at one or two cases per million people vaccinated. Young children who get the flu shot along with pneumococcal vaccine and/or DTaP vaccine at the same time might be slightly more likely to have a seizure caused by fever (CDC, 2017h).


The optimal time period when vaccination should occur is before the onset of influenza activity in a community. Healthcare providers should begin offering vaccination by the end of October whenever possible. Most adults will have a protective antibody response within two weeks following immunization. The vaccine should be offered continually as long as the influenza viruses are circulating and unexpired vaccine is available (CDC, 2017f).


The CDC, the Advisory Committee on Immunization Practices, and the Healthcare Infection Control Practices Advisory Committee recommend that all U.S. healthcare workers get vaccinated annually against influenza. Healthcare workers include (but are not limited to):

  • Physicians
  • Nurses
  • Nursing assistants
  • Therapists
  • Technicians
  • Emergency medical service personnel
  • Dental personnel
  • Pharmacists
  • Laboratory personnel
  • Autopsy personnel
  • Students and trainees
  • Contractual staff not employed by the healthcare facility
  • Persons not directly involved in patient care but potentially exposed to infectious agents:
    • Clerical
    • Dietary
    • Housekeeping
    • Laundry
    • Security
    • Maintenance
    • Administrative
    • Billing
    • Volunteers
    (CDC, 2017i)


Influenza vaccines are updated annually to provide a combination of the most likely flu strains to be in circulation. Traditional flu vaccines made to protect against three different flu viruses (trivalent) are available. Additionally, flu vaccines made to protect against four different flu viruses (quadrivalent) are available.

CDC recommends using injectable influenza vaccines only for the 2017–2018 flu season. The nasal spray flu vaccine should not be used during 2017–2018, as it has not demonstrated adequate effectiveness data. Options available this year include:

  • Standard-dose trivalent shot manufactured using virus grown in eggs, given with a needle into the muscle of the arm. Different flu shots are approved for different age groups; one trivalent vaccine formulation can be given with a jet injector for persons aged 18 through 64.
  • High-dose trivalent shot approved for people 65 and older
  • Recombinant trivalent shot that is egg-free approved for people 18 years and older
  • New trivalent shot made with adjuvant (an ingredient that helps create a stronger immune response) approved for people 65 years of age and older
  • Quadrivalent shot approved for use in different age groups
  • Intradermal quadrivalent shot injected into the skin and approved for people 18 through 64 years of age
  • Quadrivalent shot containing virus grown in a cell culture and approved for persons 4 years of age and older

Trivalent vaccine protects against three different flu viruses: the two most common influenza A viruses (H1N1 and H3N2) and one influenza B virus, whichever is predicted to be circulating in a given year. The trivalent flu vaccine available for the 2017–2018 flu season is made from the following viruses.

  • A/Michigan/45/2015 (H1N1)pdm09-like virus
  • A/Hong Kong/4801/2014 (H3N2)-like virus
  • B/Brisbane/60/2008-like virus (B/Victoria lineage)

This year’s quadrivalent vaccine contains the above three strains plus a B/Phuket/3073/2013-like virus (B/Yamagata lineage) (CDC, 2017j).

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 vaccine dosing and administration tables so that, in consultation with medical providers, they are prepared to quickly ascertain the best vaccine options for their patients.

  • Follow standard medication administration guidelines for site assessment/selection and site preparation.
  • Prepare vaccine out of line of sight of patient and/or parents (for children).
  • Position patient so that the muscle is as relaxed as possible. If using the deltoid, allow the arm to swing freely and not rest on the patient’s lap, chair arm, or any other surface.
  • Allow skin disinfectant to dry completely before injecting; this ensures adequate skin contact time and minimizes secondary pain from disinfectant.
  • To avoid injection into subcutaneous tissue, spread the skin of the selected vaccine administration site taut between the thumb and forefinger, isolating the muscle. Another technique, acceptable for pediatric and geriatric patients, is to grasp the tissue and “bunch up” the muscle.
  • Insert the needle fully into the muscle at a 90° angle and inject (do not attempt aspiration).
  • Withdraw the needle and apply light pressure to the injection site for several seconds with a dry cotton ball or gauze pad.

Source: CDC, 2016k.


On a Friday afternoon in early September, Jeanine, a 55-year-old female patient, asked Maria Jones, RN, 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 told her she thought it was still a little early but did not yet have the information for the recommendations for this season. She reassured Jeanine that she would look into it and give her a call with further information.

Over the weekend, Maria went to the CDC website and read about the new recommendations for seasonal influenza vaccinations. She found a table that showed types of vaccines available, dosing, and route information. She also located 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 used 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. She told Jeanine that the CDC recommends vaccines be given as soon as they are available and that the clinic expected to have their first doses available in early October. Maria informed her, however, that the new CDC recommendations did not include the use of nasal spray for this season, as it had not demonstrated adequate effectiveness.


A serious complication of influenza is pneumococcal pneumonia caused by Streptococcus pneumonia. It is the leading cause of vaccine-preventable illness and death in the United States. Adults 65 years and older are at greater risk for contracting this disease. Also, because some strains of this bacterium have become resistant to drugs that were effective in the past, prevention through vaccination has become even more important.

The best prevention of pneumococcal pneumonia is by vaccination with both the influenza and pneumococcal vaccines. It is recommended that:

  • Adults age 65 or older who have never received a pneumococcal vaccine or whose previous vaccination history is unknown should receive a dose of pneumococcal conjugate vaccine (PCV13) followed by a dose of PPSV23 at least one year later. PCV13 and PPSV23 should not be administered on the same day.
  • Adults age 65 or older who have already received one or more doses of PPSV23, the dose of PCV 13 should be given at least one year after receipt of the most recent PPSV23 dose.
  • Adults age 65 or older who have already received a dose of PCV13 at a younger age should not receive another dose of PCV 13.

Source: CDC, 2016l.

Public Education

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


Influenza (Flu) (CDC)

Influenza (National Institute of Allergy and Infectious Diseases)


NOTE: Complete URLs for references retrieved from online sources are provided in the PDF of this course.

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Brook I. (2016). Pediatric influenza. Medscape. Retrieved from

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Centers for Disease Control and Prevention (CDC). (2017d). Rapid influenza diagnostic tests. Retrieved from

Centers for Disease Control and Prevention (CDC). (2017e). Influenza antiviral medications: summary for clinicians. Retrieved from

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