Influenza: Difference between revisions
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Revision as of 12:51, 3 September 2015
Background
- Transmission
- Occurs in 6ft radius around infected pt who is sneezing and/or coughing
- Viral shedding lasts ~5d (starts 24-48hr before onset of symptoms)
- Longer duration of shedding occurs in children, elderly, pts w/ chronic illnesses
- Shedding from asymptomatic individuals doesn't contribute significantly to transmission
- Convalescence
- Most pts gradually improve over 2-5d, although may last for one week or more
- Some pts have persistent weakness lasting several weeks (postinfluenza asthenia)
Clinical Features
- Constitutional
- Respiratory
- Non-productive cough
- Sore throat
- Rhinorrhea
Diagnosis
- Influenza PCR preferred for inpatients (sensitivity >95%)
- RSV/Flu/metapneumovirus test low sensitivity for adults (48-60%) and children (62-72%), with turnaround time <24 hours
- The Viral Respiratory Panel (influenza, RSV, adenovirus, parainfluenzavirus) discouraged (sensitive 70-90%) with 3-5 days turnaround
- Rapid tests specific but not sensitive (cannot be used to rule-out)
Clinical Predictors
Odds that acute cough and fever are due to flu during flu season:[1]
- Adolescents ≥ 12 yo - 79-88%
- Children 5-12 yo - 71-83%
- Children < 5 yo - 64%
- Adults - unreliable predictors especially when older than 60 yo
Treatment
Risk Factors
- Age <2 years or >65 years
- Pregnancy
- Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), neurologic, neuromuscular, or metabolic disorders (including diabetes mellitus)
- Immunosuppression, including that caused by medications or by HIV
- Persons younger than 19 years of age who are receiving long-term aspirin therapy
Outpatients
- Risk factors:
- Yes
- Do NOT send Point of Care influenza test
- Do NOT send diagnostic test for influenza
- Empirically treat for influenza using antivirals if symptoms for <48 hours
- No
- Do NOT send Point of Care influenza test.
- Do NOT send diagnostic test for influenza.
- May consider treating with anti-influenza antivirals is symptoms <48 hours
- Yes
Admitted Patients
- Do not send Point of Care influenza test
- Send diagnostic test for influenza
- Influenza PCR preferred for inpatients (see Diagnosis section)
- Empirically treat for influenza using antivirals
- Most effective when administered when symptoms of influenza have occurred for < 48 hours
- May be benefit when initiated in severely ill inpatients with 48 hours to 5 days of symptoms
- No evidence of benefit after 5 days of symptoms
- Treat empirically promptly with oseltamavir unless there is an alternative diagnosis
- Droplet precautions (see below)
Medications
- Antiviral agents (neuraminidase inhibitors)
- Despite questions on efficacy and safety, CDC still recommends treatment for all hospitalized patients and outpatients at risk for complications[2]
Oseltamivir (Tamiflu)
Shorten duration of illness by 16.8 hrs while NNTH (number needed to harm) was 28 in regards to causing n/v, HA, and renal and psych syndromes[3]
Dosing
- Age <1 year: 3mg/kg PO BID x 5 days
- <15kg: 30mg PO BID x 5 days
- 15-23kg: 45mg PO BID x 5 days
- 24-40kg: 60mg PO BID x5d
- Adult: 75mg PO BID x 5 days
Zanamivir (Relenza)
Relatively contraindicated in patients w/ asthma, COPD, or pregnancy. Shorten duration of illness by 14.4 hrs with no reduction in flu-related complications[4]
Dosing:
- Age >7yo: 10mg (2 inhalations) BID x 5d
- Prophylaxis: 10mg (2 inhalations) once daily x 7 days
- Not for age < 5yo
Antiviral Agent | Recommended For | Not Recommended With | Adverse Events |
Oseltamivir (Tamiflu®) |
|
N/A |
|
Zanamivir (Relenza®) |
|
Underlying respiratory disease (e.g., asthma, COPD) |
|
Isolation Precautions
- Droplet precautions
- If the patient is in an area in which they are in contact with other patients or need to be transported and thus may come in close contact (<3 feet) with staff, visitors, or other patients, the patient needs to wear a surgical mask (or N-95 respirator, if not available).
Complications
- Pneumonia
- Primary influenza PNA
- Most severe and least common type of PNA
- Rare in otherwise healthy adults
- Consider in pts w/ persistent and worsening symptoms (esp high fever, SOB, cyanosis)
- CXR shows b/l opacities w/ or w/o superimposed consolidation
- Secondary bacterial PNA
- Exacerbation of fever and respiratory symptoms after initial improvement
- Higher fever, productive cough, radiographic evidence of infiltrates
- Microbiology
- Pneumococcus, S. aureus (including MRSA), H. flu
- Exacerbation of fever and respiratory symptoms after initial improvement
- Primary influenza PNA
- Otitis Media
- More common in children
- Myositis and rhabdo
- More common in children
- Extreme tenderness of affected muscles (most commonly in the legs)
- Pericarditis/myocarditis
- Rare complication
See Also
References
- ↑ CDC Clinical Flu
- ↑ Fiore AE, et al. Antiviral Agents for the Treatment and Chemoprophylaxis of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP). CDC. Recommendations and Reports. January 21, 2011. 60(RR01);1-24.
- ↑ Jefferson T, et al. Oseltamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments. BMJ. 2014; 348:g2545.
- ↑ Heneghan CJ, et al. Zanamivir for influenza in adults and children: systematic review of clinical study reports. BMJ. 2014; 348:g2547.