05/11/21: WCHD Health Alert Influenza Updates

Requested Actions

  • Strongly recommend influenza immunization to everyone 6 months or older, except when influenza vaccine is contraindicated.
  • Immunize your patients against influenza or connect them with a pharmacy or healthcare provider who can.
  • Be aware of optimal timing for influenza vaccine.
  • Keep abreast of local, regional, and national influenza activity.
  • Review influenza testing and treatment guidelines.
  • Report influenza deaths and outbreaks in congregate care facilities to the Health Department.


The Centers for Disease Control and Prevention (CDC) recommends influenza vaccine for everyone 6 months or older who does not have contraindications to the vaccine.

Updates in this season’s Prevention and Control of Influenza MMWR Vol. 70/No. 5 include:

  • All influenza vaccines this season are quadrivalent, offering protection against influenza A-H3N2, influenza A-H1N1, influenza B (Victoria lineage), and influenza B (Yamagata lineage). Both influenza A components are different than last year. Both influenza B components are the same as last year.
  • The best time to vaccinate people is before influenza begins to circulate in the community, typically at the end of October. However, some people should get vaccine as soon as it is available:
    • Pregnant women in the third trimester. This allows ample time for immune response before influenza begins to circulate, giving women and their newborns the best chance of protection.
    • Children under 9 years of age will need 2 doses at least 28 days apart. This ensures enough time for 2 doses before influenza begins to circulate.
  • Influenza vaccine may be given throughout influenza season, into the spring.
  • CDC clarified which vaccines are contraindicated and which may be used with precautions for people who have had allergic reactions to eggs or influenza vaccine. See Prevention and Control of Influenza MMWR Vol. 70/No. 5.
  • Influenza vaccine may be given at the same time as COVID-19 vaccine or separated by any number of days. If given at the same time, use separate anatomic sites.


Use molecular testing (i.e., PCR for influenza) for all hospitalized patients with influenza-like illnesses. Although rapid molecular testing at the point of care is becoming more available, it is often an immunoassay. These tests are useful for clinical decision-making; however, sensitivity for influenza is low, from 50-70%. Interpret results based on a person’s symptoms and influenza prevalence in the community. Positive and negative predictive values vary considerably depending upon the prevalence of influenza in the community.

  • False-positive (and true-negative) results are more likely when disease prevalence is low, typically at the beginning and end of influenza season.
  • False-negative (and true-positive) results are more likely when disease prevalence is high, typically at the height of influenza season.

When influenza actively circulates, a person with influenza-like symptoms who is at high risk for complications should be treated empirically with antiviral medication, regardless of rapid test results. People at high risk for influenza complications include:

  • Children under 5 years of age (especially those under 2 years of age).
  • People age 65 or older.
  • Pregnant women.
  • People with diabetes, asthma, heart disease, morbid obesity or other chronic health conditions.


Our influenza surveillance relies on reports from healthcare facilities and providers.

Report the following to the Health Department:

  • Lab-confirmed influenza death in a person of any age (report within 3 days).
  • Patient is suspected to have a novel influenza virus (report immediately).
  • Outbreak of influenza-like illness or lab-confirmed influenza in an institutional setting (e.g., long-term care facility) (report immediately).


Early antiviral treatment can shorten the duration of fever and symptoms and may reduce the risk of complications (e.g., otitis media in young children, pneumonia, and respiratory failure).

Early treatment of hospitalized patients can prevent death. In hospitalized children, early antiviral treatment is shown to shorten hospital stays. The medications work best when given within 48 hours of symptom onset. See CDC’s complete information on antiviral medications.


CDC recommends chemoprophylaxis for institutional influenza outbreaks. Healthcare providers may also want to prescribe chemoprophylaxis for at-risk household members of people with confirmed influenza. For more information, see the Infectious Diseases Society of America’s guidelines.

Infection Control

Place hospitalized patients or residents of long-term care facilities with suspected or confirmed influenza in droplet precautions for 7 days after illness onset or until 24 hours fever-free (without fever-reducing medication), whichever is longer.

Outpatients with influenza should stay home 4-5 days after illness onset and until 24 hours fever-free (without fever-reducing medication), whichever is longer.

Influenza and SARS-CoV-2 Cocirculation

Influenza and COVID-19 frequently have similar symptoms. Testing can help distinguish between the viruses. However, a positive test for one virus does not necessarily rule out infection with the other. Co-infection with both viruses can occur and should be considered, particularly in hospitalized patients with severe respiratory disease. It is important for clinicians to be aware of viral activity in the community to help guide decision-making.

When both viruses circulate in the community, CDC recommends empiric antiviral treatment of influenza as soon as possible for the following priority groups:

  • Hospitalized patients with respiratory illness.
  • Outpatients with severe, complicated or progressive respiratory illness.
  • Outpatients at higher risk for influenza complications who present with acute respiratory illness symptoms (with or without fever).

CDC recommends testing hospitalized patients with influenza-like illnesses for both influenza and SARS-CoV-2. Patients who are not severely ill and not at high risk for influenza-related complications can be managed via telemedicine and referred to a community testing site for COVID-19 testing.

Testing for COVID-19 is important. It identifies cases so they can be appropriately isolated and contacts quarantined. Confirmed COVID-19 cases (lab-confirmed or those who have symptoms plus close contact with a lab-confirmed case) should isolate for 10 days following symptom onset and until 24 hours fever-free (without fever-reducing medication).

References and Resources

Contacting the Health Department

360-778-6100         Main Call Line – available M-F 8:30am to 4:30pm

360-715-2588         Afterhours Answering Service – available after 4:30pm and weekends

360-778-6150         Communicable Disease Report Line – 24 hours a day 7 days a week

360-778-6103         Confidential Communicable Disease Fax – 24 hours a day 7 days a week

For more information, contact:

Whatcom County Health Department Communicable Disease Program

1500 N State Street, Bellingham WA 98225

360-778-6100 Main | 360-778-6150 24-hour Communicable Disease Program Report Line

360-778-6101 Fax