Influenza resident survival guide

Influenza Resident Survival Guide
Overview
Causes
Diagnosis
Treatment
Do's
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mounika Reddy Vadiyala, M.B.B.S.[2]

Synonyms and keywords: Approach to Influenza, Influenza algorithm, Influenza workup, Influenza management, Influenza diagnostic approach, Approach to Flu, Flu algorithm, Influenza workup, Flu management, Flu diagnostic approach

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Overview

Influenza, commonly known as the flu, is an infectious disease caused by the RNA virus called the influenza viruses A and B, belonging to the family Orthomyxoviridae. Common symptoms of influenza infection are fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. The fever and body aches can last 3-5 days and the cough and lack of energy may last for 2 or more weeks. Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus. Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, polymerase chain reaction (PCR), immunofluorescence assays, and rapid molecular assays. Sensitivity and specificity of any test for influenza might vary by the laboratory that performs the test, the type of test used, and the type of specimen tested. Among respiratory specimens for viral isolation or rapid detection, nasopharyngeal specimens are typically more effective than throat swab specimens. Antiviral drugs can diminish symptoms and shorten the time of the disease by 1 or 2 days. They also can prevent serious flu complications, such as pneumonia. For people at high-risk, treatment with an antiviral drug can mean the difference between having milder illness instead of very serious illness that could result in a hospital stay. The two main antivirals used in the treatment and prevention of influenza are oseltamivir and zanamivir. Symptomatic therapy includes analgesics, antihistamines, decongestants and cough suppressants.

Causes

Common Causes

• Influenza A
• Influenza B

Complete Diagnostic Approach

Characterize the symptoms: ❑ Fever ❑ Abrupt onset ❑ Ranges from 37.8 to 40.0°C, but it can get as high as 41.1°C (106°F) ❑ Associated with chills ❑ Headache ❑ Cough ❑ Non-productive ❑ Myalgia ❑ Chills ❑ Rhinorrhea ❑ Nasal congestion ❑ Sore throat ❑ Fatigue ❑ Pleuritic chest pain ❑ Malaise Less common symptoms: ❑ Vomiting ❑ Diarrhoea ❑ Abdominal pain ❑ Loss of appetite ❑ Dizziness ❑ Weakness

Obtain a detailed history: ❑ Age ❑ List of medications Identify persons who are at high risk of complications from Influenza: ❑ Children aged younger than 2 years ❑ Adults aged 65 years and older ❑ Persons with the following comorbidities: ❑ Chronic pulmonary disorders (including asthma) ❑ Cardiovascular disorders(except hypertension alone) ❑ Renal, hepatic, hematological (including sickle cell disease) or metabolic disorders (including diabetes mellitus) ❑ Neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy, stroke, intellectual disability (mental retardation), moderate to severe developmental delay, muscular dystrophy, or spinal cord injury) ❑ Persons with immunosuppression, including that caused by medications or by HIV infection ❑ Women who are pregnant or postpartum (within 2 weeks after delivery) ❑ Children and adolescents through 18 years who are receiving aspirin- or salicylate-containing medications and who might be at risk for experiencing Reye syndrome after influenza virus infection ❑ American Indians/Alaska Natives ❑ Persons who are morbidly obese (BMI ≥40 kg/m2) ❑ Residents of nursing homes and other chronic-care facilities.

Examine the patient: Appearance ❑ Fatigue Vital signs ❑ Fever ❑(100-104° F) ❑ Heart rate ❑ Tachycardia ❑ Respiratory rate ❑ Tachypnea Skin ❑ Flushing may be present ❑ Rash may be present ❑ Increased sweating Eyes ❑ Watery eyes ❑ Redness Nose ❑ Nasal congestion ❑ Runny nose Throat ❑ Erythema and inflammation may be present ❑ Pharyngitis Lungs ❑ Usually, lung examination is normal ❑ Findings of severe disease include: ❑ Dry cough ❑ Rales ❑ Focal wheezing

Shown below is an algorithm summarizing the diagnostic approach of Influenza according to the the Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza.

Which Patients Should Be Tested for Influenza?

During influenza activity

During low influenza activity

Outpatients (including emergency department patients)

Hospitalized Patients

Outpatients

Hospitalized Patients

❑ High-risk patients, including immunocompromised persons who present with influenza-like illness, pneumonia, or nonspecific respiratory illness (eg, cough without fever) if the testing result will influence clinical management ❑ patients who present with acute onset of respiratory symptoms with or without fever, and either exacerbation of chronic medical conditions (eg, asthma, chronic obstructive pulmonary disease, heart failure) or known complications of influenza (eg, pneumonia) if the testing result will influence clinical management ❑ Patients not at high risk for influenza complications who present with influenza-like illness, pneumonia, or nonspecific respiratory illness (eg, cough without fever) and who are likely to be discharged home if the results might :❑ influence antiviral treatment decisions or  :❑ reduce use of unnecessary antibiotics,  :❑ reduce further diagnostic testing, and  :❑ reduce time in the emergency department, or  :❑ influence antiviral treatment or chemoprophylaxis decisions for high-risk household contacts.

❑ All patients requiring hospitalization with acute respiratory illness, including pneumonia, with or without fever ❑ All patients with acute worsening of chronic cardiopulmonary disease (eg, COPD, asthma, coronary artery disease, or heart failure), as influenza can be associated with exacerbation of underlying conditions ❑ All patients who are immunocompromised or at high risk of complications and present with acute onset of respiratory symptoms with or without fever, as the manifestations of influenza in such patients are frequently less characteristic than in immunocompetent individuals ❑ All patients who, while hospitalized, develop acute onset of respiratory symptoms, with or without fever, or respiratory distress, without a clear alternative diagnosis

❑ Patients with acute onset of respiratory symptoms with or without fever, especially for immunocompromised and high-risk patients

❑ All patients requiring hospitalization with acute respiratory illness, with or without fever, who have an epidemiological link to a person diagnosed with influenza, an influenza outbreak or outbreak of acute febrile respiratory illness of uncertain cause, or who recently traveled from an area with known influenza activity. ❑ Patients with acute, febrile respiratory tract illness, especially children and adults who are immunocompromised or at high risk of complications, or if the results might influence antiviral treatment or chemoprophylaxis decisions for high-risk household contacts

Influenza virus testing methods:

Method	Types Detected	Acceptable Specimens	Time to Results	Performance
Rapid Influenza Diagnostic Tests (Antigen detection)	A and B	Nasopharyngeal swab Throat swab Nasal wash Nasal aspirate Sputum	<15 min	Low to moderate sensitivity; high specificity;
Rapid Molecular Assay (Influenza viral RNA or nucleic acid detection)	A and B	Nasopharyngeal swab Nasal wash	15-30 minutes	High sensitivity; high specificity
Immunofluorescence, Direct (DFA) or Indirect (IFA) Antibody Staining (Antigen detection)	A and B	Nasopharyngeal swab or wash Bronchial wash Nasal or endotracheal aspirate	1-4 hours	Moderate sensitivity; high specificity
RT-PCR and other molecular assays (Nucleic acid detection)	A and B	Nasopharyngeal swab Throat swab Nasopharyngeal or bronchial wash Nasal or endotracheal aspirate Sputum	Varied (Generally 1-8 hours)	High sensitivity; high specificity
Rapid cell culture (shell vials; cell mixtures) (Virus isolation)	A and B	Nasopharyngeal swab Throat swab Nasopharyngeal or bronchial wash Nasal or endotracheal aspirate Sputum	1-3 days	High sensitivity; high specificity
Viral culture (conventional) (Virus isolation)	A and B	Nasopharyngeal swab Throat swab Nasopharyngeal or bronchial wash Nasal or endotracheal aspirate Sputum	3-10 days	High sensitivity; high specificity
Table adapted from: Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza CDC Guidance for Clinicians on the Use of Rapid Influenza Diagnostic Tests

Treatment

Shown below is an algorithm summarizing the management of Influenza according to the the Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza.

Does the patient have signs and symptoms suggestive of influenza?

Yes

No

Does the patient have atypical signs and symptoms or complications associated with influenza

Is the patient being admitted to the hospital?

Yes

No

Yes

No

Will testing results influence clinical management?

Influenza testing not indicated; consider other etiologies and treatments, discharge home

Yes

No

Test for influenza; start empiric antiviral treatment while results are pending

Influenza clinically diagnosed; start empiric antiviral therapy if the patient is in high risk group for complications, has progressive disease, discharge home

Which patients should be treated with antivirals?

Adults and children with documented or suspected influenza, irrespective of influenza vaccination history

❑ Persons of any age who are hospitalized with influenza, regardless of illness duration prior to hospitalization ❑ Outpatients of any age with severe or progressive illness, regardless of illness duration ❑ Outpatients who are at high risk of complications from influenza, including those with chronic medical conditions and immunocompromised patients ❑ Children younger than 2 years and adults ≥65 years ❑ Pregnant women and those within 2 weeks postpartum

Not at high risk of complications and either: ❑ Outpatients with illness onset ≤2 days before presentation ❑ Symptomatic outpatients who are household contacts of persons who are at high risk of developing complications from influenza, particularly those who are severely immunocompromised ❑ Symptomatic healthcare providers who care for patients who are at high risk of developing complications from influenza, particularly those who are severely immunocompromised

Start Antivirals as soon as possible

Consider Antivirals

Recommended Dosage and Duration of Influenza Antiviral Medications for Treatment or Chemoprophylaxis

Antiviral Agent	Patient	Treatment (5 days)	Prophylaxis (7 days)
Oseltamivir (Tamiflu®)	Children	< 1 year: 3 mg/kg/dose twice daily > 1 year: dose depends on weight. ≤ 15 kg: 30 mg twice a day > 15 to 23 kg: 45 mg twice a day > 23 to 40 kg: 60 mg twice a day > 40 kg: 75 mg twice a day	Not recommended for children < 3 months old. 3 months to 1 year: 3 mg/kg/dose once daily > 1 year: dose depends on weight. ≤ 15 kg: 30 mg once a day > 15 to 23 kg: 45 mg once a day > 23 to 40 kg: 60 mg once a day > 40 kg: 75 mg once a day
	Adults	75 mg twice a day	75 mg once a day
Zanamivir (Relenza®)	Children	For children > 7 years 10 mg (two 5-mg inhalations) twice daily	For children > 7 years 10 mg (two 5-mg inhalations) once daily
	Adults	10 mg (two 5-mg inhalations) twice daily	10 mg (two 5-mg inhalations) once daily
Peramivir (Rapivab®)	Children	*2-12 years : One 12 mg/kg dose, up to 600 mg maximum, IV over 15-30 minutes *13-17 years : 600 mg IV over 15-30 minutes (single dose)	N/A
	Adults	600 mg IV over 15-30 minutes (single dose)	N/A
Table adapted from: Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenza

Symptomatic Therapy

Over the counter (OTC) medicines may be taken to relieve influenza symptoms, but they do not affect the virus.

Symptom(s)	OTC Medicine
Fever, Aches, Pains, Sinus pressure, Sore throat	Analgesics
Nasal congestion, Sinus pressure	Decongestants
Sinus pressure, Runny nose, Watery eyes, Cough	Antihistamines
Cough	Cough suppressant
Sore throat	Local anesthetics

Do's

• Start treatment as soon as possible (within the first 48 hours of illness), whenever indicated.

Dont's

• Do not collect or routinely test specimens for influenza from nonrespiratory sites such as blood, plasma, serum, cerebrospinal fluid, urine, and stool.
• Do not use viral culture for initial or primary diagnosis of influenza because results will not be available in a timely manner to inform clinical management.
• Do not administer once-daily postexposure antiviral chemoprophylaxis if >48 hours has elapsed since exposure.
• Children and teenagers with flu symptoms (particularly fever) should avoid taking aspirin as taking aspirin in the presence of influenza infection (especially Influenzavirus B) can lead to Reye's syndrome, a rare but potentially fatal disease of the liver.

References