Influenza

Human influenza is caused by two influenza viruses, types A and B. They are spread by airborne droplets generated when an infected person coughs and sneezes, by direct contact with nasal or throat secretions of infected persons, and less frequently by freshly contaminated articles. Uncomplicated influenza is characterized by the abrupt onset of fever, myalgia, headache, nonproductive cough, sore throat, and rhinitis. Complications include secondary bacterial sinusitis and otitis, and primary viral and secondary bacterial pneumonia.15

Active Immunization: Influenza Vaccines4,6,16,17

It is strongly recommended that all OHCP, including those in training, be vaccinated annually against influenza. Vaccination not only protects the provider, but very likely reduces the risk of healthcare-associated transmission. The annual trivalent influenza vaccines are antigenic equivalents of influenza-A (H3N2), influenza-A (H1N1), and an influenza-B virus. Each year one or more virus strains in the vaccine might change on the basis of global surveillance and the emergence and spread of new strains.

Two types of influenza vaccines are available in the U.S.: inactivated IM vaccines and a live attenuated intranasal vaccine (Table 2). The viruses contained in all influenza vaccines are grown in eggs. The live attenuated intranasal vaccine (Flumist™) is approved for use by healthy persons between the ages of 19-49 years. OHCP who choose to use Flumist™ in lieu of an inactivated influenza vaccine should refrain from contact with immunosuppressed persons for 7 days.

Table 2. Influenza Vaccines.4,6
VaccinesIndicationsSchedulesAdverse Effects
Afluria
Fluarix
FluLaval
Fluvirin
Fluzone
Preexposure1 IM dose annuallyPain at injection site (most common); fever, myalgia, and malaise can occur; anaphylaxis in persons with history of allergic reaction to egg.
Flumist™Preexposure1 intranasal dose annuallyMild rhinorrhea, nasal congestion, and sore throat; may exacerbate asthma; anaphylaxis in persons with history of allergic reaction to egg.

Antiviral Chemoprophylaxis: Antiviral Agents

Four antiviral agents are available to treat influenza: amantadine, rimantadine, zanamivir, and oseltamivir. Influenza-A viruses are resistant to amantadine and rimantadine, these agents should only be used if evidence of susceptibility to these antiviral medications has been established. Zanamivir and oseltamivir appear to be effective against both influenza-A and B viruses when treatment is instituted within 2 days of the onset of illness. Antiviral agents are not substitutes to vaccines.