SEATTLE — Along with the ongoing transmission of COVID-19, public health officials say common colds are on the rise in Seattle and King County.
The Seattle Flu Study began monitoring respiratory diseases in the Seattle area in 2018 and partnered with Public Health – Seattle & King County in early 2020 to launch the greater Seattle Coronavirus Assessment Network (SCAN) to monitor COVID-19.
Their combined data gives insights into COVID-19 mitigation efforts and the transmission of other viruses.
Based on the level of positive tests for all respiratory diseases in the summer of 2019, health officials say the causes of common colds held on through the summer alongside a measurable level of “continued flu importations.”
When comparing last summer’s data to this summer’s COVID-19 control, officials say the King County area saw “deeper and much longer suppression of respiratory disease with only the COVID-19 virus and rhinovirus enduring.”
Officials said that this summer, all respiratory disease was suppressed more and for longer than last summer largely due to different mitigation efforts put in place to help limit the spread of COVID-19.
“The same steps we take to prevent COVID-19... will also help reduce the spread of influenza and other respiratory viruses,” said Dr. Jeff Duchin, Health Officer for Public Health – Seattle & King County. “And because we need to prevent as many influenza infections as possible this season, everyone should please remember to get vaccinated.”
See data with in-depth breakdowns from health officials below:
1. Stacked histogram showing cumulative test positive fraction for 10 pathogens across the last two years in the Seattle metro area. We see that in the summer of 2020 all respiratory disease was suppressed more and for longer than in the summer of 2019. This can largely be attributed to the various mitigation efforts put in place to combat COVID-19.
"If we look closer at the data for this summer, we can see that the flu season was already winding down, but the voluntary closure of large employers, local schools, and the Stay Home, Stay Healthy order accelerated the normal seasonal decline in flu cases. Flu, RSV, common coronaviruses, and other pathogens died out quickly in response to the control measures and we are only now seeing detectable reimportations. Additionally, there is essentially a pairing between relaxing distancing restrictions (moving to phase 1.5 or 2) and additional mitigation efforts (increasingly strong mask requirements) that have helped keep the various respiratory diseases suppressed.
“There are three important lessons to learn from what we see here. First, our mitigation efforts are protecting us from more than just COVID-19. Second, our efforts are not perfect. Despite everything people have done and are doing, rhinovirus—the most common viral infection in humans and dominant cause of the common cold—continues to circulate. Third, not all circulation is equal—rhinovirus levels are still much lower and climbing more slowly than last summer, and COVID-19 levels are much lower than they would be if left unchecked.”
2. Looking at the summer of 2020 we see that the Stay Home, Stay Healthy order helped speed the end of the flu season. Combining relaxation of strict measures (going to phase 1.5 and 2) with other mitigation efforts (increasingly strong mask requirements) have managed to keep disease incidence low. However, the persistence of Covid-19 and Rhinovirus show that our efforts are not perfect in preventing the spread of respiratory disease.
“While Seattle and King County may see a very mild flu season this year due to ongoing COVID-19 mitigation efforts, the winter season still carries a risk for heightened spread of respiratory disease.”