3.Discussion
Using hospital-based and multicenter surveillance for RSV infection
among the all-age population in Beijing for four years, this study
revealed the epidemiological characteristics of RSV in Beijing from 2015
to 2019: The RSV was prevalent in the all-age population in Beijing with
only one annual epidemic season. Moreover, the RSV season started in
October, ended in March of the following year with a single peak in
Winter, and covered about 90% of RSV infections. The epidemic season’s
onset and offset times in different years may advance or be delayed by
about one month. However, the offset time of the RSV epidemic season we
observed was not consistent with Yu et al.’s
report[17]. The reason may be that they adopted
the definition of the RSV epidemic season described previously by CDC in
the U.S.[18], the consecutive weeks during which
the RSV detection rate per week exceeds a threshold of 10%, which might
be appropriate for RSV infections among children but not applicable in
this study due to the inclusion of adults. Yu et al. also reported that
RSV-A and RSV-B dominated
alternatively in different years in
Beijing from 2007 to 2015[17], but we observed
that RSV-A has remained dominant in Beijing since 2015.
This study compared the prevalence of RSV infections among the
populations of different age groups and found that the detection rate of
RSV was highest in children under five years of age (6.07%), followed
by people aged ≥60 years (1.57%).
Ren et al[19] reported that the RSV detection rate
in patients aged ≥66 years was 2% in Beijing during 2005–2007, the
same percentage Feng et al.[10] reported for the
average of RSV detection rates in patients aged ≥65 years from 22
provinces in China from 2009 to 2013. These two estimates are slightly
higher than ours, probably due to the inclusion of the 60–64 years of
age population in our study. However, our findings confirmed that the
elderly people aged ≥60 years were another RSV infection susceptible
population, accounting for 25.2% of
total RSV infections, besides the expected children under five years of
age, who accounted for 52.0%. Given that China is the world’s largest
population country and its population is aging, it can be speculated
that the proportion of RSV-infected patients with 60 years of age or
older will increase continuously shortly. So, the elderly population, 60
years of age or older, should receive full consideration when the RSV
prevention and control policy is made.
This study also found that co-infection of multiple pathogens was common
in RSV-infected cases. The most frequently identified pathogens was the
influenza virus, followed by M. pneumoniae , which might be due to
a certain overlap of the epidemic seasons of RSV, influenza virus, andM. pneumoniae in
Beijing[16].
Another contribution of this study was that we described and compared
the clinical characteristics of patients with RSV infection from
different age groups in Beijing, particularly patients 60 years or
older. We found that the many key indicators of the patients with RSV
infection among the elderly adult aged ≥60 years were significantly
higher than those among the populations of any other age group, namely,
the rate of hospitalization, the rate of ICU admission, and the rate of
death in hospital. However, the RSV detection rate of the elderly adult
aged ≥60 years was lower than that of children under five years old.
As to clinical manifestations, the most outstanding for RSV-infected
patients with ≥60 years of age was dyspnea followed by lymphocytopenia,
which was more common compared to other age groups, and occurred at a
significantly higher frequency than the RSV-infected patients under five
years of age. Regarding complications, there was an obvious difference
in the different age groups. RSV infections in elderly adults aged ≥60
years were frequently complicated by respiratory failure, heart failure,
and kidney failure compared to other populations, while acute myocardial
injury was more common in RSV infections in children under five years of
age. Notably, a total of eight RSV-infected patients with severe
pneumonia were given ECMO therapy in this study, and finally, seven
cases were cured, and one died. This favorable ratio suggests that there
may be a chance to improve the hospitalization mortality of RSV-infected
adults further and needs to be confirmed by collecting more cases.
Several studies reported the RSV infection in elderly adults focusing on
different aspects, and considered that the RSV infection led to a
heavier health burden and more severe illness in the elderly adults than
influenza[2, 20, 21]. In this study, the hospital
length of stay of patients with RSV infection was elevated as the age of
the patients increased, the hospital length of stay in RSV-infected
patients with ≥60 years was 12 days, and was longer than that of any
other age group, but was shorter than the hospital stay of 20 days
reported by Jin et al[20] for RSV-infected elderly
adults in South Korea. The hospitalization mortality of
RSV-infected patients aged ≥60 years
is 7.8%, which was also significantly higher than that of children with
RSV infection under five years of age (0%), and approximately
consistent with the study of Falsey et al. [2] on
American healthy elderly adults (mortality of 8% among RSV-infected
patients aged ≥65 years), but lower than Jin’s[20] study on the elderly adults in South Korea
(mortality of 12% among RSV-infected patients aged ≥65 years).
In
conclusion, The RSV season in
Beijing usually began in October and ended in March of the following
year and covered approximately 90% of RSV infections.
The RSV infection in the elderly
aged ≥60 years old, the second most susceptible population, usually
developed more severe outcomes than in children under five years of age,
with dyspnea and lymphocytopenia as important clinical
characteristics.These findings can promote the comprehensive
understanding of the illness course and contribute to the policy-making
on RSV prevention and control in China, particularly in Beijing.