Discussion
Many kinds of viruses can cause ARTI with various clinical symptoms.
Early detection of virus is not only beneficial for the recovery from
infection,12 but also conducive to the control of
virus outbreaks so as to avoid wider spread. Besides, it also strongly
helps epidemiological investigation.13
The present study is the first one in the past decade to investigate the
epidemiology of respiratory viruses in west China. We found that the
total number of children with ARTI in the second year was more than that
in the first year. In both years, there were more boys than girls with
similar boy: girl ratios. The majority of children with ARTI were young
boys, indicating that boys were more vulnerable to ARTI than
girls.14 The average age of the population was only
2.2 ~ 2.3 years old, and nearly 50% of the children
were less than 1 year old. The heavier burden of viral respiratory
infections in children less than 1 year might be a result of an immature
immune system and waning of maternal antibodies after 6 months old.
Then, children are able to develop antibodies by themselves between the
age of 2.5 to 3.5 years old to prevent viral infections.15
Previous epidemiological data showed that RSV was the most predominant
respiratory virus in children.16 However, our data
revealed that Flu A was the most common virus in our region. It could be
caused by the usage of more sensitive detection methods or the seasonal
variations nature of virus distributions. Our results are aligned with a
study in which Flu A was found to be the most predominant virus among
Chinese young children, followed by RSV.17 In our
study, RSV was predominantly detected in children less than 5 years old,
while Flu A and B were mainly in 5 ~ 10 years old,
suggesting that RSV is likely to be infected in the family or community,
while Flu A and B might mainly be infected in school.
The characteristics of geographical areas could significantly affect the
observed burden of each respiratory virus.9 The
weather in west China belongs to subtropical monsoon humid climate. The
monthly positive rates of the two years were mostly similar, indicating
the positive rate of viruses remains almost unchanged in the same region
unless there were a large number of imported cases. The monthly trend
has been consistent until January. The highest burden of viral infection
in the first year was recorded in January, while in comparison the
positive number in January 2020 decreased significantly, mainly due to
measures against SARS-CoV-2 such as strict home isolation and long-term
wearing of masks, which could effectively block the spread of the
viruses. The sharp decrease in the number of infection was consistent
with the data provided by the China National Influenza Center on 5 June
202018, proving that measures taken by our country
against SARS-CoV-2 were completely effective.19Compared with other viruses, the positive rates of Flu A and RSV were
higher throughout the study period. We knew that Flu A and RSV have
obvious seasonality. The positive number increased when the weather got
colder (autumn and winter) and decreased when the weather was warmer
(spring and summer). The total number of positive samples increased from
October in the past two years. Therefore, it’s reasonable to infer that
the infection rate of respiratory virus in 2020 may gradually increase
from October if less strict isolation measures would be taken because of
the blockage of SARS-CoV-2 in China.
Due to the timely adoption of various isolation measures, SARS-CoV-2,
which broke out in late 2019, did not break out widely in our region.
Besides, few cases have been observed in children and adolescents
because they have a more favorable clinical course than
adult.20 From the outbreak to 3 June 2020, our
hospital has tested all presumed cases for SARS-CoV-2 nucleic acid, as
well as SARS-CoV-2 antibody tests for 21241 hospitalized patients and
their families, but none of the test results were positive. Therefore,
the possible influence of SARS-CoV-2 on the positive rate of the seven
respiratory viruses in children could be excluded.