Influenza Viruses

Influenza virus type A and B are RNA orthomyxoviruses.17 The viruses are spread from person to person primarily via droplets generated during talking, breathing, coughing, and sneezing; and less frequently by contact with freshly contaminated articles and environmental surfaces. The typical incubation period is 1 to 4 days and its period of transmissibility is from the day before symptoms begin through 5 to 10 days after onset of illness.

Clinical Features

Uncomplicated infection is characterized by fever, myalgia, headache, malaise, nonproductive cough, sore throat, and rhinitis. Among children, otitis media, nausea, and vomiting also are commonly reported. Uncomplicated influenza illness typically resolves after 3 to 7 days for the majority of persons, although cough and malaise can persist for >2 weeks. Complications include primary viral pneumonia; and secondary bacterial sinusitis, otitis media, and pneumonia.


The best way to prevent the flu is by getting vaccinated each year. The annual flu vaccine will protect against the influenza viruses that research indicates will be most common during the upcoming season. This includes an influenza A (H1N1) virus, an influenza A (H3N2) virus, and one or two influenza B viruses, depending on the flu vaccine.

Medical Management

The antiviral drugs oseltamivir (Tamiflu), which is taken orally, and zanamivir (Relenza), which is inhaled, have generally been about 70 to 90% effective for chemoprophylaxis after exposure to susceptible strains of seasonal influenza A or B. Medical care is supportive to help relieve symptoms and to address complications such as bacterial infections.