Seasonal Influenza Activity Widespread Across the State
Seasonal influenza is hitting our region hard as we see marked increases in flu hospitalizations and deaths. So far this season, 452 Spokane County residents have been hospitalized with lab-confirmed flu and 25 have died, compared with 222 hospitalizations and 11 deaths at this same time last year. Over the past 15 flu seasons, the current season is the first time all states in the continental US have reported widespread flu activity during the same week.
Surveillance in Washington state shows that while both influenza A and B viruses are circulating throughout the state, influenza A(H3N2) viruses have been predominating so far this season. Similar seasons in the past have been associated with more hospitalizations and deaths in persons aged 65 and older and young children compared to other age groups. To date, the majority of Spokane residents who have died from flu-related complications have been in individuals over age 65.
Historically, vaccine effectiveness has been lower against A(H3N2) viruses than against influenza A(H1N1)pdm09 or influenza B viruses. Last season, vaccine effectiveness against circulating A(H3N2) viruses was estimated to be 32% in the United States (US) and the Center for Disease Control and Prevention (CDC) expects that vaccine effectiveness could be similar this year, should the trend with circulating viruses continue.
Antigenic characterization has been conducted by CDC on three influenza specimens collected in Washington state during the 2017-2018 season:
- Four influenza A (H3N2) specimens were characterized as A/Hong Kong/4801/2014-like, the influenza A (H3N2) component of the 2017-2018 vaccine.
- One influenza A specimen was characterized as A/MICHIGAN/45/2015-LIKE (H1N1)pdm09, the influenza A (H1N1) component of the 2017-2018 vaccine.
- Three influenza B specimens were characterized as B/Phuket/3073/2013-like, the B Yamagata lineage component of the 2017-2018 quadrivalent influenza vaccine.
Spokane Regional Health District (SRHD) continues to recommend flu vaccination for everyone over the age of six months, especially people at high risk of developing flu-related complications, including children younger than five, adults age 65 and older, pregnant women, residents of nursing homes and long-term care facilities, people with chronic medical conditions, and American Indians and Alaska Natives. Antiviral medications with activity against influenza are an important adjunct for prevention and treatment of influenza. Their early use in these high-risk groups has been shown to impact flu-related morbidity and mortality.
SRHD also recommends masking for unvaccinated healthcare workers when they are in direct patient care for the duration of this year’s flu season.
Further information for health professionals, including detailed vaccine recommendations, antiviral drug information, and infection control recommendations can be found at the Centers for Disease and Prevention web site.