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Vaccinate children 6 to 23 months old with IIV
Either IIV or LAIV in healthy children 2 to 18 years of age
For prophylaxis, oseltamivir dosage varies by weight and is recommended by the CDC for prophylaxis for children ≥3 months; zanamivir is approved for prophylaxis for children ≥5 years of age at a dosage of 2 inhalations per day. For prophylaxis, the dosage of amantadine and of rimantadine is 5 mg/kg/day up to 150 mg in 2 divided doses. Currently, amantadine and rimantadine are not recommended due to resistance.
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Pregnancy Considerations
The CDC recommends vaccinating all women who will be pregnant during influenza season.
If unvaccinated at the time of flu season, pregnant women should receive IIV.
Oseltamivir, zanamivir, peramivir, rimantadine, and amantadine are pregnancy Category C.
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COMMONLY ASSOCIATED CONDITIONS
Bacterial pneumonia á
DIAGNOSIS
Rule out influenza by the ABSENCE of the following: á
- Systemic symptoms
- Cough
- Not being able to cope with daily activities
- Being confined to bed
HISTORY
Sudden onset of the following: á
- Fever (37.7-40.0 ░C), especially if combined with presenting within 3 days of illness onset
- Anorexia
- Chills, sweats, malaise, myalgia, arthralgia
- Headache
- Sore throat/pharyngitis
- Nonproductive cough
- Rhinorrhea, nasal congestion
PHYSICAL EXAM
- Physical exam is not specific for influenza.
- Physical examination should exclude complications such as otitis media, pneumonia, sinusitis, and tracheobronchitis.
DIFFERENTIAL DIAGNOSIS
- Respiratory viral infections including respiratory syncytial virus, parainfluenza, adenovirus, enterovirus ("influenza-like illness"Ł)
- Infectious mononucleosis
- Coxsackievirus infections
- Viral or streptococcal tonsillitis
- Atypical mycoplasmal pneumonia
- Chlamydia pneumoniae
- Q fever
- Less likely possibilities include severe acute respiratory syndrome, primary HIV infection, acute myeloid leukemia, tuberculosis, anthrax, and malaria
DIAGNOSTIC TESTS & INTERPRETATION
Initial Tests (lab, imaging)
- During influenza season, base diagnosis solely on clinical findings. If additional testing is needed
- Reverse transcription polymerase reaction (RT-PCR) from nasopharyngeal swab or aspirate is the gold standard for diagnostic confirmation.
- CBC: typically shows normal WBC count or mild leukopenia. Leukocytosis may indicate bacterial complications.
- Direct fluorescent antibody or indirect fluorescent antibody staining for influenza antigen; results available in hours (dependent on lab expertise)
- Commercial rapid enzyme-linked immunosorbent assay antigen tests are available. Some rapid tests diagnose influenza A, whereas others diagnose A and B. Sensitivity and specificity vary by manufacturer, strain of influenza, and age of patient. False negatives are fairly common particularly during periods of peak influenza activity in the population being tested.
- Viral isolation not particularly useful except in periods of low influenza activity when making the correct diagnosis is critical.
- Imaging
- Chest x-ray if pneumonia is suspected
TREATMENT
- Symptomatic treatment is typically all that is required (saline nasal spray, analgesic gargle, antipyretics, analgesics).
- Cool-mist or ultrasonic humidifier to increase moisture of inspired air
- Droplet precautions: See http://www.cdc.gov/HAI/settings/outpatient/basic-infection-control-prevention-plan-2011/transmission-based-precautions.html#c
- 5 days is the average period of viral shedding in immunocompetent hosts.
- Hospitalized patients may require oxygen or ventilatory support.
- Tobacco cessation
MEDICATION
- Antiviral treatment depends on current resistance patterns each year; check http://www.cdc.gov/flu/ or local health department for current patterns. Antivirals are most effective if administered within first 48 hours in those with laboratory-confirmed (or highly suspected based on clinical findings) influenza illness.
- Antivirals within 48 hours of symptom onset are recommended if at risk of complications (i.e., diabetes, CHD, COPD, asthma, etc.) (1)[A].
- Antivirals are recommended if hospitalized (2)[A].
- Antivirals include amantadine, rimantadine, oseltamivir, zanamivir, and peramivir.
- Antivirals may be considered for persons not at increased risk of complications from influenza whose onset of symptoms is within the past 48 hours and who wish to shorten the duration of illness and further reduce their relatively low risk of complications (1)[A].
- Symptomatic treatment is preferred for those patients without risk factors and without signs of lower respiratory tract infection 2.
- Effect is 24-hour reduction of symptoms and a reduction in complication rates.
- Zanamivir dose: 2 inhalations BID for 5 days (age ≥7 years)
- Rimantadine dose: 100 mg BID for ages 13 to 64 years; 100 mg/day for >65 years of age
- Amantadine dose: 100 mg BID for ages 13 to 64 years; 100 mg/day for >65 years of age
- Oseltamivir dose: 75 mg PO BID for 5 days (age ÔëĄ13 years)
- If severe renal impairment, 75 mg/day PO
- Oseltamivir for children ≥1 year of age
- <15 kg, 30 mg BID
- >15 to 23 kg, 45 mg BID
- >23 to 40 kg, 60 mg BID
- >40 kg, 75 mg BID
- Oseltamivir for children <1 year of age: 3 mg/kg/dose BID
- Peramivir dose: 600 mg IV infusion over 15 to 30 minutes for adults ≥18 years of age
- Antipyretics
- Acetaminophen: in children
- Precautions
- Zanamivir may cause bronchospasm if the patient has COPD or asthma; the patient should have a bronchodilator available.
- Amantadine has anticholinergic properties and should be used with caution in those with psychiatric, addiction, or neurologic disorders, as it may increase risk for suicide attempts or increase neurologic symptoms.
- Rimantadine may increase the risk of seizures in those with an underlying seizure disorder.
- Oseltamivir may cause nausea and vomiting; may be less severe if taken with food.
- Peramivir may cause serious skin reactions.
- Amantadine and rimantadine are currently not recommended due to resistance.
- Decrease dose of certain antivirals if creatinine clearance <30 mL/min.
- Ibuprofen or other NSAIDs for symptomatic relief
- Aspirin: should not be used in children <16 years due to risk of Reye syndrome
- Outpatient treatment is sufficient except for cases with severe complications or in high-risk groups.
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
- Mild cases: Usually, no follow-up is required.
- Moderate or severe cases: Follow up until symptoms and any secondary sequelae resolve.
DIET
Increase fluid intake á
PATIENT EDUCATION
CDC: http://www.cdc.gov/flu/ á
PROGNOSIS
Good á
COMPLICATIONS
- Otitis media
- Acute sinusitis
- Croup
- Bronchitis
- Pneumonia (primary viral or secondary bacterial)
- Apnea in neonates
- Reye syndrome
- Rhabdomyolysis/myositis
- Postinfluenza asthenia
- COPD or CHF exacerbation
- Encephalopathy, death
Geriatric Considerations
Complications are more likely in elderly who are also more likely to require hospitalization.
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REFERENCES
11 Centers for Disease Control and Prevention. Influenza antiviral medications: summary for clinicians. http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm.22 Harper áSA, Bradley áJS, Englund áJA, et al. Seasonal influenza in adults and children-diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America. Clin Infect Dis. 2009;48(8):1003-1032.
ADDITIONAL READING
- Ebell áMH, White áLL, Casault áT. A systematic review of the history and physical examination to diagnose influenza. J Am Board Fam Pract. 2004;17(1):1-5.
- Grayson áML, Melvani áS, Druce áJ, et al. Efficacy of soap and water and alcohol-based hand-rub preparations against live H1N1 influenza virus on the hands of human volunteers. Clin Infect Dis. 2009;48(3):285-291.
- Lalezari áJ, Campion áK, Keene áO, et al. Zanamivir for the treatment of influenza A and B infection in high-risk patients: a pooled analysis of randomized controlled trials. Arch Intern Med. 2001;161(2):212-217.
- Osterholm áMT, Kelley áNS, Sommer áA, et al. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2012;12(1):36-44.
- Centers for Disease Control and Prevention. Influenza. Available at http://www.cdc.gov/flu/index.htm.
CODES
ICD10
- J11.1 Influenza due to unidentified influenza virus with other respiratory manifestations
- J10.1 Flu due to oth ident influenza virus w oth resp manifest
- J11.00 Flu due to unidentified flu virus w unsp type of pneumonia
- J11.89 Influenza due to unidentified influenza virus w oth manifest
- J09.X2 Flu due to ident novel influenza A virus w oth resp manifest
ICD9
- 487.1 Influenza with other respiratory manifestations
- 488.12 Influenza due to identified 2009 H1N1 influenza virus with other respiratory manifestations
- 487.0 Influenza with pneumonia
- 488.19 Influenza due to identified 2009 H1N1 influenza virus with other manifestations
- 488.82 Influenza due to identified novel influenza A virus with other respiratory manifestations
- 488.11 Influenza due to identified 2009 H1N1 influenza virus with pneumonia
- 488.81 Influenza due to identified novel influenza A virus with pneumonia
- 488.89 Influenza due to identified novel influenza A virus with other manifestations
- 487.8 Influenza with other manifestations
SNOMED
- 6142004 Influenza (disorder)
- 231000124101 Influenza A virus subtype H1 2009 pandemic strain present (finding)
- 195878008 Pneumonia and influenza (disorder)
- 441345003 Influenza B virus present (finding)
- 63039003 Influenza with respiratory manifestation other than pneumonia (disorder)
CLINICAL PEARLS
- Influenza is an acute, (typically) self-limited, febrile infection caused by influenza virus types A and B.
- With rare exceptions, all persons >6 months should be vaccinated against influenza on an annual basis.
- Complications from influenza are most common in the very young, very old, and those with preexisting comorbidities.
- Hand hygiene either with soap and water (slightly superior) or with alcohol-based hand rubs and covering coughs are simple ways to reduce the spread of influenza.