Results
In the three years prior to the pandemic, there were over 2000 ED visits for bronchiolitis per year, averaging 3.1% of all visits seen (Table 1). In 2020, there were 450 visits for bronchiolitis, representing 1% of all ED visits, a statistically significant decrease in mean bronchiolitis visits over the 5 years of study, (F = 4.5, p=0.003). All years had higher mean bronchiolitis visits compared to 2020, Tukey’s HSD for year to year comparisons, (alpha=0.05),|2017 vs 2020|=146.4167 (p=0.0358); |2018 vs 2020|=149.75 (p=0.03); |2019 vs 2020|=157.6667 (p=0.0196); |2020 vs 2021|=191.0833 (p=0.0027). In the second year of the pandemic (2021), bronchiolitis visits had the highest proportion of ED visits for the 5 study years at 4% in addition to having the highest number of visits (2743 visits). Race/ethnicity, gender and age were similar between study years. There was an increase in rates of patients with bronchiolitis admitted to the hospital in the first year of the pandemic at 44% but returned to previous rate of 38% the following year. Viral testing was performed on 11% of patients on average, which increased to 35% during the pandemic but again decreased the year after. In the pre-pandemic period (2017-2019), RSV was positive in 43% of samples versus 29% in the pandemic period (2020-2021) (z=4.9, p<0.0001). In 2020 alone only 4% of viral testing was positive for RSV, followed by a sharp rebound to 63% in 2021-2022 (Table 1 and Figure 2). Rhino/enterovirus was detected in 92% of viral samples in 2020 (Table 1 and Figure 1). While there were no patients diagnosed with bronchiolitis with COVID-19 through the first year of the pandemic, 31% tested positive in the second year (Table 1 and Figure 1).
Multiple measures were analyzed to assess acuity of visits including estimated severity index (ESI), admission unit and use of high flow. There was no difference in ESI scores pre-pandemic compared to pandemic; median ESI’s were 3 for all study years except for 2018 with median ESI of 4 (Table 1). During 2020, 22% of patients with bronchiolitis were admitted to the ICU, which represented a significant increase (p<0.05) compared to all other study years (Table 2). In the second year of the pandemic, only 9% of patients were admitted to the ICU. There was a statistically significant increase (p<0.05) in high flow usage in 2020 with 23% of patients being placed on high flow. Chest radiographs increased in the first year of the pandemic compared to the other study years with 37% compared to 24%-31% in other years. Albuterol use in 2020 was 29%, compared to 15% in 2021 and 20% and 24% in the 2 years prior to the pandemic.
In addition to changes in overall yearly visit numbers, there was a shift in the seasonality of visits (Figure 2). Higher numbers of bronchiolitis visits were seen in late fall and winter in the pre-pandemic years. During the first year of the pandemic, there was a uniform decrease in visits for bronchiolitis, with the exception of March 2020. In 2021, there is a spike in bronchiolitis in the summer months of June and July with almost 500 visits each month and lower numbers during the winter months.