Influenza [IDSA]

Key Points ÎÎInfluenza illness is caused by infection with 1 of 3 types of circulating RNA viruses: influenza A, B, or C virus. Influenza C virus infection causes respiratory illness that is generally milder than influenza A and B virus infections and for which diagnosis, treatment, and prevention are generally not pursued. ÎÎDuring influenza season, influenza viruses circulate ubiquitously in the population. Each year, between 5% and 20% of the population are infected with influenza viruses, and an estimated annual average of 36,000 deaths and over 200,000 hospitalizations attributable to influenza virus infection occur in the United States. ÎÎThe elderly, the very young, and persons with underlying medical conditions such as those with cardiopulmonary disease, persons with diabetes, immunocompromised persons, morbidly obese persons, and pregnant women are at increased risk for severe disease or death secondary to influenza virus infection. ÎAppropriate use of diagnostic testing, along with timely administration Î of antiviral medications, may improve clinical outcomes of influenza virus infection, may reduce other unnecessary diagnostic testing, may decrease duration of required medical care, and may reduce both appropriate use (for presumed bacterial complications) and inappropriate use (to prevent bacterial complications) of antibacterial agents. Shedding Time ÎÎImmunocompetent persons: may be up to 5 days from onset ÎÎInfants and young children: commonly 1 week or longer ÎÎImmunocompromised persons: may be several weeks Vaccination In general, inactivated influenza vaccine is contraindicated for, and should not be administered to, persons known to have anaphylactic hypersensitivity to eggs or to any vaccine components. Recombinant influenza vaccine (Flublok®) can be given safely to such persons. Guillain-Barré syndrome within 6 weeks following a previous dose of influenza vaccine is considered a precaution for use of influenza vaccines. ÎÎInfluenza vaccination is the primary tool to prevent influenza, and antiviral chemoprophylaxis is not a substitute for influenza vaccination. •  Quadrivalent vacccines provide protection against both lineages of influenza B virus whereas trivalent vaccines contian only one B lineage. ÎÎInfluenza vaccine should be administered as soon as vaccine is available, and vaccination efforts should continue until influenza is no longer in the community (B-II). ÎÎVaccination is particularly important for all family members when 1 person or more is at high risk of complications (A-I). ÎÎChildren aged <9 years who receive inactivated influenza vaccine for the first time require 2 doses of vaccine, with the second dose

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