Influenza Season 2019–2020

David Sotello MD

DOI: 10.12746/swrccc.v8i33.653

Influenza season has already started! The usual peak activity months are December through February, although an important number of influenza cases can be seen as late as May. According to the Centers for Disease Control and Prevention (CDC), there has been a rise in reported cases of influenza since week 45 of 2019.1 Until week 48 of 2019 up to 10.2% of respiratory specimens by clinical laboratories nationwide (total 26,576 specimens) have tested positive for influenza; most of the cases are secondary to influenza B (71.1%), followed by H1N1 and H3N2 viruses.1 During week 48, an estimated 3.5% of patient visits (total of 1,194,381 patients) reported through the Influenza-like Illness Surveillance Network (ILINet) were due to influenza-like illness. This estimate has surpassed the national baseline of 2.4%; this increased activity was reported mostly in Puerto Rico, Alabama, Georgia, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, South Carolina, Tennessee, Texas, and Washington.1

It is important that health care providers and the general population participate in seasonal influenza prevention. The CDC strongly recommends to vaccinate against influenza virus everyone 6 months of age and older every season, especially persons at high risk, which includes adults 65 years of age and older, pregnant women, young children, patients with chronic lung disease, cardiovascular disease, chronic kidney disease, diabetes, HIV/AIDS, cancer patients, other immunocompromised patients, and children with neurologic conditions. This season there are multiple immunization options, including quadrivalent influenza vaccine, high-dose influenza vaccine (65 years and older), nasal spray influenza vaccine (live attenuated), jet injector (Afluria®), and intradermal influenza vaccine. It is important to tailor the immunization strategy according to each patient’s characteristics and needs.2

Antiviral medications may be required for treatment and chemoprophylaxis (oseltamivir and zanamivir) in selected cases. There are currently four medications approved in the United States for treatment Influenza: oseltamivir, zanamivir (inhaled), peramivir (intravenous) which are neuraminidase inhibitors, and baloxavir marboxil (endonuclease inhibitor). Amantadine and rimantidine are no longer recommended. If treating influenza, these drugs are usually recommended within 2 days of illness onset in otherwise healthy patients or when they are at high risk for influenza-related complications, hospitalized patients, those with severe, complicated, or progressive illness.3

Keywords: Influenza, infection, prevention, season

Submitted: 12/14/2019


  1. Centers for Disease Control and Prevention. Weekly U.S. Influenza Surveillance Report. Last accessed 12/11/2019. Available at:
  2. Centers for Disease Control and Prevention. Prevent Seasonal Flu. Last accessed 12/11/2019. Available at:
  3. Centers for Disease Control and Prevention. Influenza Antiviral Medications: Summary for Clinicians. Available at: