Dear Editor,
Pengcheng Liu
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reported that influenza virus activity dropped sharply among children in Shanghai,
China, during the COVID-19 pandemic. According to their research, the infection was
close to zero in the early stage of the COVID-19 pandemic. At present, the COVID-19
epidemic in China has entered the postpandemic period; consequently, the Chinese government
has announced 10 measures to optimize COVID prevention and control work since 7th
December. There is public concern that SARS-CoV-2 will circulate with other respiratory
viruses and increase the probability of coinfections. Therefore, we further explored
influenza virus coinfections with SARS-CoV-2 during 7th November 2022 and 31st December
2022 before and after the new policy.
COVID-19 poses a great challenge to China's medical and health system, either since
the battle of Wuhan and Hubei in 2019 or the battle against Delta and Omicron to date.
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China has a large population. In response to the outbreak, in the past three years,
China has organized and mobilized massive human and material resources and adopted
strict epidemic prevention measures, such as checking health codes when entering public
places, landing inspections for migrants between provinces, checking travel codes,
etc. MMoreover, standardized good hygiene habits are required in daily life, such
as wearing masks in public and washing hands frequently, which have been demonstrated
to be very effective in delaying SARS-CoV-2 transmission and remarkably decreasing
the incidence and death rate worldwide.
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However, these anti-epidemic measures have had a great impact on the social economy
and daily life. On December 7th, 2022, the Chinese National Health Commission announced
ten prevention and control measures to further optimize the COVID-19 response. These
new measures include scrapping negative nucleic acid results and health code requirements
for entering nonspecial public places and domestic cross-regional travel, changing
landing inspection into self-home quarantine in particular asymptomatic carriers and
mild COVID-19 patients. The new Ten optimization measures are based on the Omicron
variant with weakening “pathogenicity”, the popularization of vaccination, and the
accumulation of COVID-19 prevention and control experience and have again taken an
important step toward precision and science.
To extrapolate the influence of the adjustment, we counted the children who visited
the Children's Hospital of Zhejiang University outpatient and inpatient departments
(from November 7, 2022 to December 31, 2022) before and after the introduction of
the new ten optimization measures. According to the survey, since December 7th, 2022,
the number of positive patients with COVID-19 has continued to rise, and on December
22nd, the number of positive patients reached 887, with a positive rate of 68%. After
a small peak of infection, the number of infected patients showed a rapid downward
trend. This phenomenon is because since December 21, 2022, patients in medical institutions
no longer require nucleic acid testing as a mandatory requirement. In line with this
policy, the number of people taking part in the test has dropped significantly, and
the corresponding number of positive patients has also decreased, but the positive
rate has remained above 40%, indicating that the actual number of infected people
is still increasing (Fig. 1
A, Fig. 2
A).
Fig. 1
Number of total and positive specimens of SARS-CoV-2 and respiratory influenza viruses.
(A) SARS-CoV-2; (B) Mycoplasma pneumoniae (MP); (C) adenovirus (ADV); (D) influenza
A virus (FluA); (E) influenza B virus (FluB); (F) respiratory syncytial virus (RSV).
The vertical axis and colored lines on the left show the number of positive specimens
for SARS-CoV-2 and respiratory influenza virus. The right vertical axis and the gray
line represent the number of total specimens.
Fig 1
Fig. 2
Proportion of SARS-CoV-2 and respiratory influenza virus positives (A) and proportion
of coinfections (B).
Fig 2
Although the severe disease rate and mortality rate are not as high as the original
strain, it still places great pressure on medical institutions. To make matters worse,
in the season of high incidence of respiratory viruses such as influenza, respiratory
virus coinfections with COVID are more likely to occur. In the past three years, wearing
masks and other epidemic prevention measures have rapidly decreased the infection
rate of common respiratory viruses such as influenza, but these measures have also
reduced people's immunity to those respiratory pathogens. The liberalization of epidemic
prevention and control measures may cause a pandemic of these respiratory viruses,
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which increases the risk of combined common respiratory virus infections, such as
influenza in COVID-19. Coinfection is usually considered to lead to more severe symptoms
and worsen the clinical outcome of patients with COVID-19. A study from the State
Key Laboratory of Virology, Wuhan University
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found that in COVID-19 receptor human ACE2 transgenic mice, coinfection with influenza
and COVID-19 can cause more serious pathological damage to the lung and a higher COVID-19
load, which also means that it may lead to more serious secondary diseases. They found
that the expression of ACE2 was slightly upregulated (2∼3 times) by influenza alone
but strongly upregulated (approximately 20 times) by influenza coinfection with COVID-19[6].
We inferred from the article that influenza virus infection can increase coronavirus
infection by initiating the expression of ACE2 and accelerating the subsequent expression
process. At the same time, the study also shows that
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viral infection may worsen the clinical outcome and significantly increase the probability
of acute kidney injury, acute heart failure, secondary bacterial infection, multileaf
infiltration and ICU admission.
In fact, according to our data, there are few people with coinfection. We selected
five kinds of respiratory influenza viruses for research during this period, including
Mycoplasma pneumoniae, adenovirus, influenza A virus, influenza B virus and respiratory
syncytial virus, which appeared as seasonal epidemics in our hospital in previous
years (Fig. 1). However, according to our data, after the rapid increase in SARS-CoV-2
infection, coinfection of SARS-CoV-2 with these viruses is very rare, only 0.23% (Fig.
2). The most important reason should be that although the country has lifted restrictions
on the movement of people, the public's awareness of wearing masks has become stronger.
Our previous research shows that nonpharmaceutical interventions such as wearing masks
and washing hands can be useful to limit the infection of common respiratory viruses,
which is an effective measure to block respiratory virus infection in COVID-19.
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In summary, nonpharmaceutical intervention is an effective measure to block SARS-CoV-2
coinfections with common respiratory virus infections.
Declaration of Competing Interest
The authors report no conflicts of interest.