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\begin{document}

\title{The Changing Virology and Trends in Resource Utilization for
Bronchiolitis since COVID-19}



\author[1]{Mary Orr}%
\author[1]{Allison Burks}%
\author[1]{William King}%
\affil[1]{The University of Alabama at Birmingham Department of Pediatrics}%


\vspace{-1em}



  
  \date{May 18, 2024}


\begingroup
\let\center\flushleft
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\endgroup





\selectlanguage{english}
\begin{abstract}
Background: Bronchiolitis is a viral respiratory illness most commonly
caused by respiratory syncytial virus (RSV). COVID-19 disrupted typical
patterns of viral transmission. Our study aimed to compare low value
care for bronchiolitis in a tertiary emergency department (ED) in the
United States over the previous five years. Methods: This was a
descriptive cohort study through a retrospective chart review from
2017-2022 analyzing ED visits for bronchiolitis including disposition,
disease severity, chest radiographs, albuterol, and high flow nasal
cannula. A year was a 12 month period from March to February. Results:
In the three years prior to the pandemic, there were over 2000 ED visits
for bronchiolitis per year (3.1\% of all ED visits), which decreased to
450 visits for bronchiolitis (1\% of all visits) in 2020. Human
rhino/enterovirus was the most common virus detected (92\%). Admission
rates, albuterol use, high flow nasal cannula use, and chest radiographs
were all higher during the first year of the pandemic. The summer of
2021 had the highest visits across the 5 study years (2743, 4.0\% of all
visits) with a return to previous rates of resource utilization.
Conclusions: During the early pandemic, measures to halt the spread of
COVID-19 also altered the transmission of RSV and emergency visits for
bronchiolitis. There was an increase in lower value care while the
volume was low and rhinovirus was the dominant virus detected. As
restrictions lifted in 2021, there was a large resurgence of RSV in the
atypical summer months with a return of previous rates of resource
utilization.%
\end{abstract}%



\sloppy


\textbf{Introduction}

Bronchiolitis is a common disease affecting children from infancy to 24
months with inflammation and mucous production in the distal bronchioles
that can progress to significant respiratory distress {[}1-3{]}. It is
most commonly due to respiratory syncytial virus (RSV) but can be caused
by numerous other viruses including human rhinovirus, metapneumovirus,
influenza, adenovirus, coronavirus, and parainfluenza virus {[}3-5{]}.
Bronchiolitis is the most common cause of hospitalizations for infants
less than 12 months of age and incurs a large financial burden on the
United States health system at over \$400 million dollars per year {[}3,
6{]}. According to the Centers for Disease Control, traditionally RSV
peaks in December through March in North America with some regional
variations. The treatment is largely supportive, and guidelines
recommend against routine use of chest radiographs, albuterol, steroids,
and corticosteroids {[}1{]}. More recently, evidence does not support
early use of high flow nasal cannula in mild to moderate bronchiolitis
{[}Franklin 7, Keprotes 8{]}. Despite these guidelines, use is
widespread and recently was the target of a national quality improvement
project {[}Byrd 9{]}.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID-19)
developed in late 2019 and quickly spread globally in the spring of
2020, causing a worldwide pandemic {[}10{]}. Many measures and practices
were put in place to try to slow the spread including social distancing,
increased hand hygiene, face coverings in public places, ``Stay at Home
Orders'', and mandatory closures of many businesses and schools. Early
on in the pandemic, emergency departments saw a significant decline in
patient encounters, including a decline in pediatric visits for
respiratory complaints {[}11{]}. A sharp decline in bronchiolitis was
noted in the Southern Hemisphere while COVID-19 cases were rising
{[}12{]}. A decrease in RSV cases continued worldwide during the first
year of the pandemic in 2020 to early 2021 {[}4, 12-15{]}. Previous
studies have focused on all emergency department (ED) visits or just
inpatient visits during the pandemic, but there is a lack of information
about changing patterns of bronchiolitis ED visits after more recent
rebounds, as well as how the changing volumes affect typical emphasis of
decreasing low value interventions.

This descriptive study aimed to compare bronchiolitis visits at a large
tertiary care pediatric ED in the southeast United States after the
onset of COVID-19 compared to the three years prior. Secondary aims
included comparing markers of visit acuity, virology, resource
utilization and general demographics of the study population to
determine if bronchiolitis ED visits consumed more resources after the
onset of the pandemic.

\textbf{Materials and Methods}

This study was a retrospective cohort study performed at a tertiary
children's hospital in the Southeastern US with annual ED visits of
74,000 before the pandemic. All emergency department visits for patients
under 24 months of age from March 2017 through February 2022 with an
ICD-10 diagnosis code for bronchiolitis (J.21) coded at any time during
their hospital stay. There were no exclusion criteria. Demographic
information including age, gender, race and ethnicity were collected
form the medical record. Visit information including acuity (based on
triage Emergency Severity Index level), disposition (admitted,
discharged, expired), admission unit, use of high flow nasal cannula,
albuterol, and chest radiographs during ED visit or after admission,
along with viral respiratory testing results were extracted. Viral
respiratory testing from nasopharyngeal swabs included three possible
panels that could be ordered at the prescriber's discretion including a
viral respiratory panel (VRP) polymerase chain reaction that tested for
15 common viruses as well as Sars-CoV-2, RSV, and influenza antigen
detection, and a rapid BioFire\selectlanguage{ngerman}® FilmArray® respiratory panel. Human
rhinovirus is not distinguished from other enteroviruses on these tests
and is reported as ``rhino/enterovirus.'' Data from the three years
prior to the pandemic (2017, 2018, 2019) were compared with ``pandemic
years'' 2020 and 2021. A year was a 12 month period from March to
February to help align with the emergence of COVID within the United
States in March of 2020.

Basic database management and analysis of descriptive statistics were
performed using Excel and SSPS statistical software. Comparisons of
differences among and within the 5 year study samples were accomplished
using the One Way ANOVA with post hoc pairwise multiple year comparisons
using Tukey's HSD at alpha =0.05. For nonparametric group analyses,
Kruskal-Wallis ANOVA with the post hoc multiple group Bonferroni
correction with an alpha of 0.005 was used. Year to year comparisons of
the proportions of use of therapies, medications, orders or unit
specific admissions was performed using a 95\% confidence interval
estimation of the differences of proportions (no continuity correction).
Intervals of the difference in proportions not inclusive of 0 were
considered statistically significant at p\textless{}0.05. This study was
approved by the University of Alabama at Birmingham Institutional Review
Board under exempt category four, protocol number IRB-300006644-004. The
datasets generated during and/or analyzed during the current study are
not publicly available, but are available from the corresponding author
on reasonable request.

\textbf{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),\textbar{}2017 vs
2020\textbar{}=146.4167 (p=0.0358); \textbar{}2018 vs
2020\textbar{}=149.75 (p=0.03); \textbar{}2019 vs
2020\textbar{}=157.6667 (p=0.0196); \textbar{}2020 vs
2021\textbar{}=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\textless{}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\textless{}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\textless{}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.

\textbf{Discussion}

COVID-19 nearly erased bronchiolitis and RSV infections within our
emergency department during the first year of the pandemic, with over
80\% reduction in bronchiolitis visits from the year prior. While all ED
visits fell, the proportion of visits due to bronchiolitis also
decreased. The marked decline in respiratory illness is likely
multi-factorial and is hypothesized to be largely driven by social
distancing, hand hygiene, masking, and Stay at Home Orders {[}11{]}.
This trend was also noted in other parts of the world including Belgium,
New Zealand, Brazil, France, and the US {[}12-15{]}. While other studies
have focused on ICU patients or all cause ED visits, this study adds
detailed information with a large cohort of bronchiolitis ED visits in
the Southeastern US with measures of resource utilization and changes in
virology as cases of bronchiolitis fell dramatically and then rose
sharply.

The 2014 AAP Guidelines for the management of bronchiolitis recommends
against routine chest radiographs and albuterol use {[}1{]}. Despite
this, over use still occurs in many hospitals. The pandemic brought
about many changes in how respiratory illnesses were acutely managed due
to the novelty of COVID-19 and fears that it would be more severe in
young children. However, none of the patients in 2020-2021 actually
tested positive for COVID. Increased use of high flow, albuterol, chest
radiographs and ICU admissions for bronchiolitis were seen during the
lower volume period when rhinovirus was the dominant pathogen detected.
Other studies have shown that providers are more likely to utilize
diagnostic tests and medications once high flow is initiated, and
increased use of low value care for bronchiolitis during lower census
periods has been described {[}18, 19{]}. Prior studies have not shown an
increase in bronchiolitis severity during this time {[}20{]}. In
2021-2022, 31\% of patients tested had COVID, a substantial increase
likely reflecting increased lower respiratory symptoms with changing
variants, but albuterol and decreased. The resurgence of bronchiolitis
after such a dramatic decrease means this disease is likely never going
to completely disappear. Ironically, concentrating quality improvement
efforts into periods of low census for a disease may have more impact.

This hospital saw a stark change in the virology of patients seen in the
ED with bronchiolitis over the course of the study period. There was an
initial disappearance of RSV in the first year of the pandemic with only
four RSV cases identified in 2020 among our study population. An
atypical summer spike in RSV in 2021 followed, which is likely the
primary driver in the increased bronchiolitis visits. The summer ED
visits were almost as high as the winter of the last typical season in
2019. During the low volume year of 2020, rhino/enterovirus was the
predominant virus detected by percentage, though the raw number detected
was relatively similar to previous years. It is possible that more
rhinovirus was detected due to higher testing rates, which increased by
23\% from the year prior. Rhinovirus is often found to be a co-infection
with a large number of asymptomatic carriers but is also known to cause
bronchiolitis, especially associated with wheezing, and may be an early
predictor of asthma {[}21-24{]}. It is possible that more albuterol was
used during this time due to more rhino/enterovirus induced wheezing
heard on exam.

The dominance of rhino/enterovirus during the emergence of the pandemic
and the disappearance of RSV raises important questions about how the
transmission of this virus was affected by efforts to slow the spread of
COVID. RSV is an enveloped, single\selectlanguage{english}-stranded, negative\selectlanguage{english}-sense RNA virus of
the Pneumoviridae family and is transmitted via droplet {[}24{]}.
Because of its enveloped structure, RSV is more affected by hand washing
then the non-enveloped structure of rhinovirus, which has a moderate
resistance to hand sanitizer {[}24, 25{]}. RSV's main reservoir is in
chronic obstructive pulmonary disease and immunocompromised hosts,
whereas rhinovirus is often carried and spread by asymptomatic healthy
children {[}1, 25{]}. Hand washing was heavily stressed as a
non-pharmaceutical intervention during the pandemic and could have
decreased RSV transmission but would not have the same impact on
rhinovirus. The relative resilience of rhinovirus during the pandemic
likens it to the cockroach of viruses- one that never completely
disappears and survives most extinguishing efforts.

Immunity to RSV is complex. For infants, the transfer of maternal
antibodies can help protect them in the first couple months of life
{[}27{]}. Adults also need continued antigenic exposure, as it has been
shown there is a loss of RSV-specific IgA memory B-cells, usually in the
summer months when RSV is dormant {[}27{]}. It is reasonable to
hypothesize there was decreased maternal antibody transfer to infants by
mothers who were pregnant during the early COVID pandemic and were not
being exposed to RSV antigens. Therefore it is not surprising there was
a large, atypical RSV spike in the summer of 2021 (Figure 2) when there
was likely a large population of infants and toddlers who were
immunologically naive to RSV being exposed for the first time. As COVID
precautions relaxed in the spring of 2021, RSV was able to have a strong
resurgence. The rise in bronchiolitis visits in the summer of 2021 also
followed the end of the state mask mandate in this state, which expired
in April of 2021. In the future, we will see if this shift in RSV
seasonality persists with bronchiolitis becoming a relatively steady
year-round illness, or return to previous seasonal norms. This could
influence the timing of Synagis given to eligible infants, as it is
currently only available during the winter months. It also remains to be
seen if other Sars-CoV-2 variants will cause more respiratory illness in
this population, as is suggested by the upwards trend in 2021-2022.

This study is limited by being a single-institution, retrospective
study. The diagnosis of bronchiolitis was based on ICD-10 coding only
and testing from other sources prior to admission were not included. The
increased ICU admission rate for bronchiolitis is difficult to interpret
as ICU admission criteria changed such that all patients on high flow
nasal cannula were admitted to the ICU instead of the step-down unit
until their COVID test resulted until November 2020, though the numbers
were very small. During 2021 this hospital participated in a Value in
Inpatient Pediatrics high flow initiation reduction quality improvement
project (HIFLO), which may account for some of the decreased high flow
rate from 2020 to 2021. Internal quality improvement projects targeted
albuterol use which likely accounts for the sharp decrease from 2017 to
2018.

In summary, COVID-19 had a significant impact on bronchiolitis emergency
department visits in overall number, admission rates, an increase in low
value care, and virology, while not being the predominant driver of
respiratory disease in young children.

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