What are the risk factors associated with symptomatic SARS-CoV-2 and rhinovirus infection in King County, Washington, from June 2020 to July 2022?

In a recent study published in JAMA Network Open, researchers evaluated the change in symptoms and risk factors associated with positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) tests during the coronavirus disease 2019 (COVID-19) pandemic and compared it to those associated with positive tests of other respiratory viruses such as rhinovirus among residents of King County, Washington, in the United States.

Study: Trends in Risk Factors and Symptoms Associated With SARS-CoV-2 and Rhinovirus Test Positivity in King County, Washington, June 2020 to July 2022. Image Credit: Kateryna Kon/Shutterstock


Studies have shown that the risk factors and symptoms associated with COVID-19 have changed since the onset of the pandemic. The severity of COVID-19 varies based on demographic and socioeconomic factors such as race and income. However, the changing symptoms and risk factors during the pandemic have not been explored comprehensively.

The non-pharmaceutical mitigation measures such as masking, hand-washing, and social distancing, as well as lockdowns during the early stages of the pandemic, have also reduced the circulation of other respiratory pathogens.

However, rhinovirus, which causes upper respiratory tract infections in adults and children, has been an exception, with the incidence of rhinovirus infections returning to the original levels after an initial decrease during the early stages of the COVID-19 pandemic.

About the study

In the present study, the researchers gathered data using the Seattle Coronavirus Assessment Network, which comprised a 25-month (June 2020 to July 2022) assessment of the risk factors and symptoms associated with positive SARS-CoV-2 tests among adults and children. This cross-sectional surveillance study also monitored the incidence of other respiratory pathogens among the participants.

The participants were supplied with free testing kits that allowed the self-collection of nasal swab samples, which were then tested using polymerase chain reaction (PCR) for 25 respiratory pathogens, including SARS-CoV-2 and rhinovirus. Furthermore, the spike protein target gene was used to identify the Delta and Omicron variants.

While assessing risk factors, the study considered all the individuals who tested negative for SARS-CoV-2 as the control group, while the individuals who tested positive, including coinfections with rhinovirus, were considered SARS-CoV-2 cases. An additional sensitivity analysis was conducted by excluding coinfection cases. Rhinovirus cases comprised all individuals that tested positive for rhinovirus without SARS-CoV-2 coinfections, while the corresponding control group consisted of individuals who tested negative for both rhinovirus and SARS-CoV-2.

The analysis included socio-demographic variables such as age, sex, social and economic risk index, county region, and race and ethnicity. Additional health behavior, demographic risk factors, and self-reported indicator variables for 16 SARS-CoV-2 symptoms were also included in the analysis. The community incidence of SARS-CoV-2 was determined using the weekly log of SARS-CoV-2 cases in the county.


The results reported that the risk factor and symptom variables most commonly associated with COVID-19 incidence were close-contact with a SARS-CoV-2-positive individual and loss of taste or smell, respectively. Contact with SARS-CoV-2 positive individuals who were vaccinated decreased the probability of testing positive for SARS-CoV-2 compared to contact with unvaccinated SARS-CoV-2 positive individuals.

When symptoms and risk factors were analyzed according to variants of concern, the probability of testing positive for SARS-CoV-2 after close contact with an infected individual and symptoms of anosmia and dysgeusia were lower for the Omicron variant. Individuals infected with the Omicron variant also reported more sore throats than infections with the Delta variant.

The risk factors associated with positive rhinovirus tests were fewer compared to SARS-CoV-2. Children below the age of 12 seemed more susceptible to rhinovirus infections. Additionally, socio-demographic factors such as race (Black persons), county region of residence (south King County), and the number of people in the household (five or more) were seen to be associated with a higher incidence of rhinovirus. The positive tests for rhinovirus were not correlated with SARS-CoV-2 positive tests, and there was a 10-to-12-week separation between each viral peak.

The authors reported that many of the risk factors and symptoms associated with the early phases of the pandemic reduced or disappeared during the later stages, especially during the period of dominance of the Omicron subvariants.

While the easing of non-pharmaceutical mitigation measures could have resulted in unaccounted asymptomatic contacts of infected individuals, the increased vaccination coverage and administration of booster vaccines could also have lowered the onward transmission risk of the Omicron variant.


Overall, the results indicated that the symptoms and risk factors associated with SARS-CoV-2 infections had changed during the course of the pandemic, with attenuation of symptoms and reduced probability of SARS-CoV-2 infections through close contact with infected individuals during the dominance of the Omicron variant.

Inequalities in risk factors and symptoms based on socio-demographic factors such as race and economic status were present during all phases of the COVID-19 pandemic, as well as in rhinovirus infections.

Journal reference:
  • Hansen, C. et al. (2022) "Trends in Risk Factors and Symptoms Associated With SARS-CoV-2 and Rhinovirus Test Positivity in King County, Washington, June 2020 to July 2022", JAMA Network Open, 5(12), p. e2245861. doi: 10.1001/jamanetworkopen.2022.45861. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2799348

Posted in: Medical Science News | Medical Research News | Disease/Infection News

Tags: Anosmia, Children, Coronavirus, Coronavirus Disease COVID-19, covid-19, Dysgeusia, Gene, Omicron, Pandemic, Polymerase, Polymerase Chain Reaction, Protein, Respiratory, Respiratory Tract Infections, Rhinovirus, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Spike Protein, Syndrome

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Written by

Dr. Chinta Sidharthan

Chinta Sidharthan is a writer based in Bangalore, India. Her academic background is in evolutionary biology and genetics, and she has extensive experience in scientific research, teaching, science writing, and herpetology. Chinta holds a Ph.D. in evolutionary biology from the Indian Institute of Science and is passionate about science education, writing, animals, wildlife, and conservation. For her doctoral research, she explored the origins and diversification of blindsnakes in India, as a part of which she did extensive fieldwork in the jungles of southern India. She has received the Canadian Governor General’s bronze medal and Bangalore University gold medal for academic excellence and published her research in high-impact journals.

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