Seasonal Influenza (Flu): Health Alert Network ADVISORY

Background

The risk of severe disease and complications from influenza is higher among children younger than 5 years of age, adults aged 65 years and older, pregnant women, and those with underlying medical conditions. In most influenza seasons, the majority of influenza-associated hospitalizations and deaths are among adults aged 65 years and older . However, during the 2009 pandemic, pH1N1 caused more illness in children and young adults than in older adults . This was likely due in part to protection in older adults provided by cross-reactive immunity to pH1N1 caused by prior infection with antigenically-related viruses. The pandemic also was notable for reports of severe illness among pregnant women infected with pH1N1 and adverse neonatal outcomes .

Early observations from the 2013-14 influenza season indicate that some persons infected with pH1N1 virus have had severe illness. While most of these people with severe illness have had risk factors for influenza-associated complications, including pregnancy and morbid obesity, several have not.

CDC recommends annual vaccination as the best tool for prevention. However, for persons with suspected or confirmed influenza, treatment with neuraminidase inhibitor antiviral drugs (oral oseltamivir and inhaled zanamivir) can be an important component of clinical care. Evidence from past influenza seasons and the 2009 H1N1 pandemic has consistently shown that treatment with antiviral medications reduces severe outcomes of influenza when initiated as soon as possible after illness onset.

Clinical trials and observational data show that early antiviral treatment may:

• shorten the duration of fever and illness symptoms
• reduce the risk of complications from influenza (e.g., otitis media in young children, pneumonia, respiratory failure and death)
• shorten the duration of hospitalization.

Recommendations for Health Care Providers

• Clinicians should encourage all patients 6 months of age and older who have not yet received an influenza vaccine this season to be vaccinated against influenza. There are several flu vaccine options for the 2013-2014 flu season (see http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6207a1.htm?s_cid=rr6207a1_w#Tab1), and all available vaccine formulations this season contain a pH1N1 component; CDC does not recommend one flu vaccine formulation over another.
• Clinicians should encourage all persons with influenza-like illness who are at high risk for influenza complications (see list below) to seek care promptly to determine if treatment with influenza antiviral medications is warranted.

 

Summary of CDC Recommendations for Influenza Antiviral Medications for Health Care Providers for the 2013-2014 Influenza Season

• CDC guidelines for influenza antiviral use during 2013-14 season are the same as during prior seasons. Clinical benefit is greatest when antiviral treatment is administered early. When indicated, antiviral treatment should be started as soon as possible after illness onset, ideally within 48 hours of symptom onset. However, antiviral treatment might still be beneficial in patients with severe, complicated, or progressive illness, and in hospitalized patients and in some outpatients when started after 48 hours of illness onset, as indicated by clinical and observational studies.
• Antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who

• is hospitalized
• has severe, complicated, or progressive illness
• is at higher risk for influenza complications.

This list includes:

• children aged younger than 2 years;
• adults aged 65 years and older;
• persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], 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);
• persons aged younger than 19 years who are receiving long-term aspirin therapy;
• American Indians/Alaska Natives;
• persons who are morbidly obese (i.e., body-mass index is equal to or greater than 40); and
• residents of nursing homes and other chronic-care facilities.
• Antiviral treatment can also be considered for suspected or confirmed influenza in previously healthy, symptomatic outpatients not at high risk on the basis of clinical judgment, especially if treatment can be initiated within 48 hours of illness onset.

• Clinical judgment, on the basis of the patient’s disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, is important when making antiviral treatment decisions for outpatients.
• Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza.
• Rapid influenza diagnostic tests (RIDTs) have limited sensitivities and predictive values; negative results of RIDTs do not exclude influenza virus infection in patients with signs and symptoms suggestive of influenza. Therefore, antiviral treatment should not be withheld from patients with suspected influenza, even if they test negative.
• While influenza vaccination is the best way to prevent influenza, a history of influenza vaccination does not rule out influenza virus infection in an ill patient with clinical signs and symptoms compatible with influenza.