Assessing the Impact of Comorbidities on Respiratory Virus Prevalence Across Age Groups in Washington State

Background. Respiratory viruses, such as respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and parainfluenza viruses (PIV) 1-4 cause significant disease burden. Vaccines against RSV are now in use in the United States to protect specific populations, including older adults and young infants, and hMPV and PIV vaccines are in development. There are few data on community-based estimates of RSV, hMPV and PIV in individuals with comorbidities, particularly in younger adults. These data are needed to identify additional at-risk groups who would benefit particularly from vaccination.
Methods. We conducted active surveillance for ambulatory care visits for acute respiratory illness (ARI) among members of a health care provider network, Kaiser Permanente Washington (KPWA), a site in the US Flu Vaccine Efficacy Network. Enrolled participants provided respiratory specimens which were tested for 12 respiratory viruses via polymerase chain reaction. We estimated the prevalence of infection due to each virus by age group and comorbidity. Results. The KPWA population who presented for ARI and received swab tests consisted of 4,335 unique individuals tested from 2018 to 2023. After rhinovirus (106 per 1000), RSV (93 per 1000), hMPV (63 per 1000), and PIV (50 per 1000) were the most detected viruses. Prevalence of RSV was highest in the youngest (0-5) and oldest (60+) age groups. However, cases followed a more heterogenous distribution among individuals with comorbidities, where individuals under 60 with cancer, chronic liver disease, pulmonary disease, diabetes, or a history of organ transplant had higher prevalences than adults above 60 without comorbidities. RSV prevalence also differed by racial/ethnic groups, with higher prevalences of RSV among individuals who self-identified as Black, American Indian/Alaska Native, or Native Hawaiian/Pacific Islander. Conclusions. Among individuals with ARI symptoms under 60, we found that individuals with comorbidities such as cancer, chronic liver disease, and a history of organ transplants, as well as individuals of Black, Native Hawaiian, or American Indian/Alaska Native race/ethnicity had a higher prevalence of RSV infection. Clinical recommendations for vaccination and prevention should consider the impact of comorbidities to minimize morbidity related to respiratory viruses among high-risk populations.