What is Influenza?

Influenza is a highly contagious airborne disease that occurs in seasonal epidemics and presents as an acute febrile illness with variable systemic symptoms.

The seasonal strains in the annual cycle are a serious public health concern, but far more lethal strains emerge periodically.
Influenza also infects animals. Some strains are species-specific, but new strains can spread from other animals to humans.

Pathophysiology

Influenza viruses are enveloped, negative-sense, single-stranded RNA viruses of the family Orthomyxoviridae.

Core nucleoproteins distinguish the 3 types: influenza A, B, and C (IAV, IBV, ICV).
Hemagglutinin and neuraminidase drive virulence and are the major targets of neutralizing antibodies.
Hemagglutinin binds respiratory epithelial cells, allowing cellular infection.
Neuraminidase cleaves the bond holding newly replicated virions to the cell surface, letting the infection spread.
Species specificity is partly due to how a given hemagglutinin binds different sialic acid receptors on respiratory tract epithelial cells.

Statistics and Incidences

In tropical areas, influenza occurs year-round.

The WHO estimates annual epidemics cause about 3-5 million cases of severe illness and about 290,000 to 650,000 respiratory deaths worldwide; seasonal flu infects as many as 1 billion people each year (WHO). This revised range replaced the older 250,000 to 500,000 estimate as data from more countries was added.
The CDC notes the often-cited figure of 36,000 annual flu-related deaths came from years when the predominant subtype was H3N2, which tends to be more lethal than H1N1.
For the 2019-2020 season, 55,000 influenza-related hospitalizations were reported as of early January 2020, and 2900 attributable deaths, including 27 pediatric deaths.

Causes

Influenza results from infection with 1 of 3 basic types: A, B, or C.

Direct contact. Transmission from poultry or pigs to humans occurs predominantly through direct contact with infected animals.
Unhygienic food preparation. Risk is especially high during slaughter and preparation. Eating properly cooked meat poses no risk.
Aerosol transmission. Viruses spread human to human via aerosols from coughs and sneezes. A susceptible person inhales the aerosol, and if secretory antibodies do not neutralize it, the virus invades airway and respiratory tract cells.
Contact with contaminated objects. Excrement from infected birds and contaminated surfaces or water are also routes of infection.

Clinical Manifestations

Presentation varies but usually includes many of the following.

Cough. Respiratory symptoms may start minimal and progress: nonproductive cough, cough-related pleuritic chest pain, dyspnea.
Fever. Ranges widely. Some run low fevers, others as high as 104°F, with reported feverishness and chills.
Sore throat. May be severe and last 3-5 days, and is often why patients seek care.
Myalgia. Common, mild to severe.
Weakness. Severe fatigue can stop normal activity or work. Patients need extra sleep, and some are bedridden.

Assessment and Diagnostic Findings

Rapid diagnostic tests for influenza are available and increasingly used.

Rapid diagnostic tests. The FDA cleared 7 rapid influenza diagnostic tests that detect influenza A or B antigens or enzyme in throat swabs, nasal swabs, or nasal washes, with results within 30 minutes. Examples: QuickVue Influenza A+B test (Quidel), ZstatFlu (ZymeTx), and QuickVue Influenza test (Quidel).
Viral culture. May require 3-7 days, often too late to guide drug therapy.
Polymerase chain reaction (RT-PCR). Testing of nasopharyngeal and throat secretions is the criterion standard for confirming infection and the only in vitro test cleared by the FDA for use with lower respiratory tract specimens.
Direct immunofluorescent tests. Available on fresh specimens but labor- and personnel-intensive and less sensitive than culture.
Serologic testing. Several tests avoid the cost and delay of culture, but most are not bedside tests. They generally take 30-60 minutes for their multiple steps, with sensitivities of 60-70%.
Testing for avian influenza. A rapid nasopharyngeal swab test specific to H5N1 (Arbor Vita Corporation) was approved by the FDA in 2009.
Chest radiography. Indicated in elderly or high-risk patients with pulmonary symptoms to exclude pneumonia. With avian influenza, pulmonary infiltrates appear in almost all patients, ranging from diffuse or patchy infiltrates to lobar or multilobar consolidation.

Medical Management

Prevention is the most effective strategy.

Vaccines. The ACIP (CDC) and the American Academy of Pediatrics recommend routine annual influenza vaccination for all persons aged 6 months or older, preferably before influenza activity begins in the community.
Surveillance. Daily temperature checks, prompt reporting, isolation through home medical leave, and segregation of smaller subgroups slow spread.
Bed rest. Most patients recover in 3 days, though malaise may persist for weeks.
Hospitalization. Usually needed when influenza worsens underlying chronic disease, when elderly patients are too weak to care for themselves, or when the direct effects of influenza require it.
Prehospital care. Mostly supportive. Give supplemental oxygen for respiratory symptoms or hypoxia. Ventilatory support with a bag-valve-mask or field intubation may be needed in respiratory failure. Obtain IV access and give a crystalloid bolus to support hemodynamic stability.
Consultations. Consult infectious disease in some cases, and intensive care specialists for severe disease.

Pharmacological Management

The goals are to reduce morbidity and prevent complications.

Antivirals. The drugs for treatment and chemoprophylaxis are the neuraminidase inhibitors (oseltamivir and zanamivir) and the cap-dependent endonuclease inhibitor baloxavir marboxil (treatment only). Neuraminidase inhibitors act on viral proteins, decreasing virulence. Baloxavir marboxil inhibits cap-dependent endonuclease, halting viral replication.
Vaccines, inactivated. Given each year before flu season. The trivalent formulation contains 3 strains (2 influenza A and 1 influenza B) chosen to match the strains expected to circulate. Quadrivalent vaccines containing 2 influenza A and 2 influenza B strains are available.
Vaccines, live. The ACIP recommended return of the intranasal vaccine in the United States for the 2018-2019 season, based on a US study in children aged 2 years to younger than 4 years that evaluated shedding and antibody responses of the H1N1 strain in the live attenuated influenza vaccine (LAIV).
Uricosuric agents. Agents that inhibit tubular secretion of the active metabolite of oseltamivir may be used as adjunctive therapy.

Nursing Management

Nursing Assessment

History. Assess the patient's travel history.
Physical examination. Assess respiratory status for rate, depth, ease, use of accessory muscles, and work of breathing. Auscultate the lung fields for wheezes, crackles (rales), rhonchi, or decreased breath sounds.

Nursing Diagnosis

Ineffective airway clearance related to tracheobronchial and nasal secretions.
Ineffective breathing pattern related to inflammation from viral infection.
Hyperthermia related to exposure to infection.
Acute pain related to influenza virus.
Deficient knowledge related to the disease process.

Nursing Care Planning and Goals

Patient will achieve and maintain a patent airway.
Patient will achieve and maintain a normal respiratory pattern and rate, with no adventitious breath sounds.
Patient will achieve and maintain a normal temperature.
Patient will achieve relief from aches and pain.
Patient will understand and verbalize appropriate treatment and care.

Nursing Interventions

Maintain a patent airway. Give oxygen as ordered. Monitor oxygen saturation by pulse oximetry and notify the physician of readings <90% or as prescribed. Position in high or semi-Fowler's. Give bronchodilators as ordered. Perform postural drainage and percussion as ordered. Encourage fluids up to 3-4 L/day unless contraindicated. Encourage deep breathing and coughing exercises every 2 hours.
Maintain a normal breathing pattern. Perform chest physiotherapy, chest percussion, and postural drainage as ordered. Encourage position changes every 2 hours and as needed. Provide fluid intake of at least 2 L/day unless contraindicated.
Achieve a normal temperature. Monitor vital signs, especially temperature, every 2-4 hours and as needed, using the same method each time. Give antipyretics as ordered. Provide tepid sponge baths. Teach the patient and family the use of a hypothermia blanket and the signs of complications.
Achieve relief from pain. Give analgesics as ordered. Provide warm baths or a heating pad for aching muscles. Encourage gargling with warm water and throat lozenges. Teach deep breathing, relaxation, guided imagery, massage, and other nonpharmacologic aids.
Educate patient and family. Keep teaching sessions short and the environment quiet. Inform vaccine recipients of possible adverse effects and report them immediately. Teach about influenza types, when outbreaks occur, and how to avoid infection. Teach about antiviral drugs, their effects, side effects, and when to seek immediate care.

Evaluation

Goals are met when the patient:

Achieved and maintained a patent airway.
Achieved and maintained a normal respiratory pattern and rate, with no adventitious breath sounds.
Achieved and maintained a normal temperature.
Achieved relief from aches and pain.
Understood and verbalized appropriate treatment and care.

Documentation Guidelines

Individual findings, including factors affecting the patient, interactions, nature of social exchanges, and specifics of behavior.
Cultural and religious beliefs and expectations.
Plan of care.
Teaching plan.
Responses to interventions, teaching, and actions performed.
Attainment or progress toward the desired outcome.

Frequently Asked Questions

Who should get the flu vaccine? The CDC recommends routine annual influenza vaccination for everyone aged 6 months and older, ideally before flu activity picks up in the community (CDC). Older adults, young children, pregnant patients, and people with chronic conditions are at higher risk and especially benefit.

How is influenza different from a common cold? Flu tends to come on suddenly with fever, body aches, severe fatigue, and cough, while colds are milder and develop gradually. The systemic symptoms (high fever, myalgia, profound weakness) point toward influenza.

What is the best test to confirm flu? RT-PCR of nasopharyngeal and throat secretions is the criterion standard and the only in vitro test cleared by the FDA for lower respiratory tract specimens. Rapid antigen tests give results in about 30 minutes but are less sensitive.

When are antiviral drugs useful? Neuraminidase inhibitors (oseltamivir, zanamivir) and baloxavir marboxil work best when started early, generally within 48 hours of symptom onset. They shorten illness and lower the risk of complications, especially in high-risk patients.

How many people die from seasonal flu each year? The WHO estimates about 290,000 to 650,000 respiratory deaths worldwide annually, with 3 to 5 million cases of severe illness (WHO). Most deaths occur in older adults and people with underlying conditions.

How long is someone with the flu contagious? Adults can spread influenza from about one day before symptoms start to roughly 5 to 7 days after becoming sick. Young children and people with weakened immune systems may shed virus longer, which is why hand hygiene and staying home matter.

Influenza Nursing Care Management and Study Guide