Clinical Analysis of 9 Cases of Neonatal Inuenza A

Background: The population is generally susceptible to inuenza A, while neonatal cases are relatively rare. The study aims to explore the clinical characteristics, diagnosis, treatment, and prognosis of neonates with inuenza A. Methods: The clinical data from neonates with inuenza A who were treated in the neonatal department of Beijing Ditan Hospital aliated with Capital Medical University from November 2017 to January 2019 were retrospectively analyzed. Results: A total of 9 neonates with inuenza A were admitted and treated, with a distribution of 7 males and 2 females. The onset was 1.44 ± 1.46 days (mean ± SD), and age at diagnosis was 21.44 ±6. 53 days. All cases had a history of exposure to febrile patients, The main symptoms are fever, nasal congestion, runny nose, sneezing, coughing, other respiratory symptoms and digestive symptoms such as vomiting milk, choking milk, less milk, diarrhea. Laboratory tests showed 7 cases of decreased white blood cell counts, 3 cases of increased plasma C-reactive protein concentrations. All cases were administered antiviral therapy on the day of admission. Eight neonates reverted to a normal temperature within 48 hours after hospitalization, one neonate’s temperature returned to normal after 48 hours of hospitalization, and all cases' symptoms gradually improved. Conclusion: The symptoms of inuenza A in neonates are atypical, once a diagnosis is conrmed, the prognosis is likely to be favorable as long as antiviral treatment with antiviral is initiated as soon as possible.


Background
In uenza viruses are divided into types A, B, and C. The principal cause of in uenza pandemics is type A, while a few pandemics are type B; and type C only causes insigni cant or mild upper respiratory tract infections. In the in uenza season, more than 40% of preschool children and 30% of school-age children contract in uenza [1] . Symptoms such as laryngitis, tracheitis, bronchitis, bronchiolitis, pneumonia, and gastrointestinal symptoms caused by in uenza A virus are also more common in children than in adults [2] . Children and immunocompromised in uenza A patients often experience complications and may even die. Infants and neonates are at high risk of in uenza A due to their relatively weaker immune function and tendency to develop serious complications such as pneumonia, and this predicts a poor prognosis [3] . As a special population, neonates may exhibit different routes of infection, clinical manifestations, treatment options, and outcomes of in uenza virus infection relative to children of other ages. At present, there are few studies that focus on neonatal in uenza A virus infection in China or internationally. Therefore, we retrospectively analyzed the clinical data from 9 neonates diagnosed with in uenza A who were admitted and treated at our hospital over the past 2 years, and also analyzed and summarized their clinical characteristics in order to improve clinical diagnosis and treatment of neonatal in uenza.
The study was approved by the Ethics Committee of Beijing Ditan Hospital a liated to Capital Medical University.

Subjects And Methods
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Research subjects
Neonates with a diagnosis of in uenza A infection who were admitted to the pediatric department of our hospital from November 2017 to January 2019 were selected as research subjects.
Inclusion criteria were (1) age in days at diagnosis ≤ 28 d; (2) a recent contact history of fever patients; (3) having 1 of the following clinical manifestations-fever, stuffy nose, runny nose, coughing, sneezing, choking on milk, spitting up milk, poor appetite, and diarrhea; and (4) a nasal/pharyngeal swab screening test that was positive for in uenza A virus antigen.
Exclusion criteria were individuals with nasal/pharyngeal swab screening who tested positive for in uenza A virus antigen, but showed no obvious in uenza-like symptoms; and no recent history of exposure to febrile patients.
Diagnosis of In uenza A [4] . A. Clinical diagnosis: the above-mentioned clinical manifestations of in uenza occurred in the case, and there was epidemiologic evidence or a positive rapid in uenza antigen test, and other diseases causing in uenza-like symptoms were excluded. B. Con rmed diagnosis: the neonate exhibited the above clinical manifestations of in uenza, and demonstrated positive results with 1 or more of the following pathogenic tests-(1) positive detection of in uenza virus nucleic acid, (2) positive isolation and culture of in uenza virus, and (3) levels of in uenza virus-speci c IgG antibody in both sera of the acute and recovery phases that increased 4-fold or more.

Data collection:
We collected general information of neonates, including gender, gestational age, birth weight, time of onset, age in days at diagnosis, duration of fever, length of hospital stay, clinical manifestations, physical signs, laboratory test results, treatment, and prognosis.

Laboratory detection method for in uenza A virus
: nasal/pharyngeal swab specimens were collected from all cases on the day of admission. The insertion depth of the swab was approximately the linear distance from the nostril to the ear lobe. The specimens were collected and placed in sealed plastic tubes with screw caps, and sent to the Department of Laboratory Medicine, Beijing Ditan Hospital, Capital Medical University for testing. An immuno uorescence method was used to detect in uenza virus antigen, and real-time RT-PCR was used to detect in uenza A virus nucleic acid.

Statistical
Analysis: Measurement data that conformed to a normal distribution are described as means ± standard deviation (x̄ ± s), and measurement data that were not normally distributed are described as medians. Descriptive statistics are expressed by a proportion (%).

General information
A total of 9 neonates with in uenza A were diagnosed, with all of them term infants-including 7 males and 2 females. There were 6 cases of natural delivery and 3 cases of cesarean delivery. The mean gestational age was 39.0 ± 0.86 weeks, and mean birth weight was 3577.44 ± 330.72 g. The age at onset was 3-28 days, and the median age was 22 days. All neonates had a history of contact with febrile patients, including 2 cases of fever in the mother and 7 cases of fever in other relatives. The mean age at diagnosis was 21.44 ± 6.53 days. None of the mothers of the 9 neonates were vaccinated against in uenza during their pregnancies. The length of hospital stay was 4-8 days, with a mean of 5.1 ± 1.5 days.

Clinical manifestations
Fever occurred in 7 of the 9 neonates, with a maximally attained body temperature of 39.5°C and a duration of 1-6 days, with an average of 2.4 ± 1.7 days. There were 6 cases of respiratory symptoms, including 4 cases of nasal congestion, 3 cases of coughing, and 3 cases of runny nose and sneezing. There were 5 cases of digestive system symptoms, including 3 cases of reduced milk intake, 2 cases of spitting up and choking on milk, and 1 case of diarrhea. The physical signs included 8 cases of pharyngeal congestion, 2 cases of coarse breath sounds and audible coarse rales, and 1 case of mottled skin.
Liver enzymes, however, were normal. Eight cases showed a positive in uenza A nucleic acid test, of which 5 cases were positive for HIN1 nucleic acid, 3 cases were positive for universal nucleic acid test (see Table 1). Five neonates underwent chest radiography and 2 neonates showed complications of pneumonia; and 6 of the 9 neonates underwent ECG examinations, with no obvious abnormalities.

Severe cases
A total of 3 neonates were diagnosed as severe cases. One neonate had a fever lasting > 3 days with pneumonia, 1 neonate had pneumonia, 1 neonate exhibited elevated myocardial enzymes, and 2 neonates manifested pneumonia without serious complications such as respiratory failure, pleural effusion, pneumothorax and atelectasis; there were no deaths.

Treatment and prognosis
The 9 neonates were treated with antiviral drugs on the day of admission (paramivir for 2-5 days, which was discontinued after body temperature improved; or oseltamivir for 5 days), and no steroids were administered.Among them, 8 neonates reverted to a normal temperature within 48 hours, and clinical symptoms improved (1 neonate was treated with gamma globulin for recurrent high fever).The other neonate manifested fever for 5 days at the time of admission, complicated by bacterial infection.His symptoms gradually improved after the application of paramivir, cefmetazole, and gamma globulin, and his body temperature returned to normal 6 days after admission. A follow-up chest X-ray showed resolution of in ammation in the lungs. None of the 9 neonates showed any adverse drug reactions or serious complications, and all of them had a favorable prognosis.

Discussion
The general population is susceptible to in uenza virus transmission via droplets, aerosols, and direct or indirect contact. Typical clinical manifestations are systemic symptoms such as sudden chills, high fever, headache, general soreness, and weakness; while the respiratory symptoms are mild [6] . In our study, the age at onset for neonates with in uenza A was 3-28 days. After birth, these neonates had an obvious history of contact with febrile patients (mother or other family members), and all of them developed symptoms during the in uenza incubation period-which is consistent with the typical course of in uenza A. The principal source of infection for neonates with in uenza A is their caregivers, although the neonates have atypical symptoms due to their low immunity. In addition to fever, nasal congestion, runny nose, sneezing and coughing in neonates with in uenza A in our study, digestive symptoms such as spitting up and choking on milk, anorexia, and diarrhea are also relatively common-which is consistent with previous reports [7][8] . Neonates with in uenza A may have reduced white blood cell and neutrophil counts, and slightly increased C-reactive protein; but whether antibiotic treatment is needed depends upon the comprehensive assessment of neonatal symptoms, physical signs, and laboratory tests so as to avoid antibiotic abuse.
In the present study, all cases were positive for in uenza A virus antigen, and the positivity rate for nucleic acid testing for in uenza A virus was 88.9%. One of the cases was negative for nucleic acid testing, but we could not exclude a false-negative due to the collection site of the specimen being unsatisfactory. However, in combination with typical fever symptoms and contact history with febrile patients, all 9 neonates met the clinical diagnostic criteria for in uenza A; and 8 neonates met the de ned diagnostic criteria for in uenza A.
Prompt diagnosis and early antiviral treatment are the most important strategies for treating in uenza. Antiviral treatment is best for neonates within 48 hours of symptoms, but for neonates with severe illness or a high risk of complications, antiviral treatment should still be considered 48 hours after symptoms appear [9] . One neonate in the present study was started on antiviral therapy 5 days after the onset of the disease, and the prognosis was still favorable despite the long treatment time. At present, oral oseltamivir is still the rst choice for treating childhood in uenza; but paramivir can also be a treatment of choice for neonates at certain dosages (see Table 2 for speci c dosages). Therefore, early detection, early diagnosis, and early treatment are the primary means to be used to reduce the mortality and serious complications of neonatal in uenza [10] .
In uenza virus infection during pregnancy can increase the risks of spontaneous abortion, premature delivery, stillbirth, and low birth weight [11][12] . Pregnant women, especially after infection in the third trimester, can also easily develop critical illnesses that can result in death [13] . In uenza vaccination of pregnant women not only effectively prevents maternal in uenza during the in uenza season, but also produces protective antibodies that can pass through the placental barrier; and thus effectively prevents infection in infants under 6 months of age who are not suitable for in uenza vaccination [14][15] . In developed countries such as the United States, the in uenza vaccination rate for pregnant women has approached or exceeded 50% [16][17] , while the in uenza vaccination rate of pregnant women in China has been very low [18] . The latest guidelines suggest [19] that pregnant women be vaccinated at any stage of pregnancy, and that the prevention of contracting in uenza by infants under 6 months of age occur through the vaccination of their mothers during pregnancy, and also of their family members and caregivers.
In summary, the symptoms of neonatal in uenza A are often atypical. In addition to fever, nasal congestion, runny nose, sneezing, coughing, and other respiratory symptoms; digestive symptoms such as spitting up milk, choking on milk, reduced milk intake, and diarrhea are also relatively common. Early diagnosis and antiviral treatment can effectively improve clinical symptoms and reduce complications, and paramivir is relatively safe for neonatal use.

Declarations FINANCIAL SUPPORT:
Open Project of the Key Laboratory of Beijing Ditan Hospital, Capital Medical University (DTKF201803).

CONFLICTS OF INTREST:
All authors declare that they have no con icts of interest.