| Background:Influenza is an acute infectious respiratory disease caused by the influenza virus.Influenza A is the main strain,accounting for about 90% influenza pathogens in northern China.Because the influenza A virus is prone to mutate,which easily causes large-scale human-to-human transmission.In recent years,the incidence of influenza in China had shown an upward trend,and it had shown a sharp increase in early 2019.More notably,during the influenza season of early 2019,there was an epidemic of influenza A among hospitalized patients.Hospital-acquired influenza A that aims at patients with primary diseases undoubtedly brings additional treatment burden and risk.Lungs are vulnerable to Influenza A virus,and part of patients can progress to viral pneumonia with a dangerous condition.Understanding the recent epidemic situation of influenza in this region,and analyzing the overall incidence trend,will improve the attention to disease and awareness of prevention.Center for Disease Control and Prevention of United States recommends high-risk groups of influenza include individuals older than 65,young children,pregnant women,patients with underlying illnesses,but this standard applies to most of infectious diseases.How to identify susceptible individuals in hospital inpatients and curb the prevalence of influenza A in the hospital is an unavoidable problem in nosocomial infection control.Currently,there are few reports on the risk factors of nosocomial infection.Also there is no unified definition of hospital-acquired influenza A,mainly because there is a 1-7 days incubation period for influenza A,so the epidemiological definition of nosocomial bacterial infections: the time interval from admission to diagnosis needs more than 48 hours cannot be used well for hospital-acquired influenza A;moreover,part of the research on the risk factors of nosocomial infection is not strict enough with the control group and did not exactly match the same period inpatients in the same department,so its conclusion was questionable.In addition,influenza A infection may cause viral pneumonia,especially in severe and critically ill patients,with rapid progress and high mortality.At present,there are many places worthy of discussion for its identification,early intervention and treatment.Objective:1.To investigate the influenza epidemic trend of recent years in Xi’an,and collect the information including age,sex,occupation,and the number of cases per year(month).To provide scientific reference for influenza vaccination and timing,and guide regional prevention and control.2.Based on the cases of influenza A in a large local level A tertiary teaching hospital from winter 2018 to spring 2019,master the epidemiological rules of this round of community-acquired influenza A.Clarify the departmental distribution characteristics of influenza A cases among inpatients,and compare the positive diagnosis rates of suspected influenza A patients in different departments,which help to take targeted measures to the epidemic of influenza A in hospitals.3.To explore the risk factors of hospital-acquired influenza A for identifying susceptible individuals early and prevent the spread of nosocomial infections effectively.4.A timely summary of the clinical features,treatment and outcome of severe influenza A viral pneumonia is conducive to improve the understanding of the disease,accumulate experience,and guide diagnosis and treatment.Methods:1.Cross-sectional study,descriptive analysis of influenza epidemic data from 2014 to2019 obtained from Xi’an Center for Disease Control and Prevention(only four items of patient’s age,gender,occupation and diagnosis time).2.Cross-sectional study,on the basis of medical records of outpatients and inpatients who had influenza-like illness and were further confirmed by viral nucleic acid real-time RT-PCR in a large tertiary hospital in Xi’an from December 2018 to April 2019,descriptively analyze the epidemiological characteristics such as visit time,gender,age,and departmental distribution of patients with influenza A,χ~2 test is applied to compare the difference in the positive diagnosis rate of patients with suspected influenza A among different groups.3.A 1: 1 matched case-control study,in which patients in the control group had no infection of influenza A during hospitalization.Matching factors:(1)Environment:Considering the process of patients exposed to the source of infection to onset(the incubation period is up to 7 days),the matched control individual should have been hospitalized for 7 days or more in the same department.(2)Age: the age difference of each matched control case was less than 5 years.Univariate analysis and conditional logistic regression analysis were used to find independent risk factors for hospital-acquired influenza A.4.Cross-sectional study,descriptive analysis of the clinical characteristics,treatment and prognosis of 13 cases of severe influenza A viral pneumonia treated in the intensive care unit of the Department of Respiratory Medicine during the two influenza seasons from winter 2017 to spring 2018 and winter 2018 to spring 2019.Results:1.(1)Xi’an influenza epidemic in recent 5 years: 602 cases in 2015;2771 cases in 2016;9471 cases in 2017;9997 cases in 2018;and 65404 cases were accumulated only from January to April in 2019.Time distribution: the incidence of influenza in winter and spring was the highest,with 41.5% of the cases in December and 30.6% in January of the following year.The incidence of summer was the lowest,with 0.4%,0.3%,and 0.4% in June,July,and August respectively.(2)Xi’an influenza outbreak season from December 2018 to April2019: Male accounted for 51.9% and female accounted for 48.1%.Age characteristics: The proportion of preschool children reached to 55%.Occupational distribution: 26.8% were children in kindergarten,24.3% were children in diaspora(referring to children aged 0 to 3years who had not entered kindergarten),and 23.8% were students(university,high school,primary school).2.Epidemiological characteristics of acquired influenza A of inpatients and outpatients of a level A tertiary teaching hospital in Xi’an from December 2018 to April 2019:(1)Community-acquired influenza A: 1012 confirmed cases,537 males,475 females.The positive diagnosis rate of suspected patients was 53.7% in December,47.6% in January,26.2% in February,14.6% in March,and 7.8% in April,with an average of 33.1%;mainly concentrated in infectious disease clinics(fever clinic)with 389 cases,342 cases in emergency department,148 cases in respiratory department,77 cases in pediatric department.Age was right skewed,with a median age(interquartile range)of 32.5(25-52)years,with a minimum of 5 months and a maximum of 92 years.(2)412 cases of infections were detected in hospitalized patients.The highest detection cases was found in geriatrics,neurology,and renal medicine.The average positive diagnosis rate of patients with suspected influenza A in all inpatient departments was 30.8%,and Nephrology(61.4%)and Geriatrics(45.6%)had a higher positive diagnosis rate than the average level(P <0.05);98cases of hospital-acquired influenza A were diagnosed.3.Univariate analysis showed that there was a significant difference in lymphopenia,hypoalbuminemia,and pleural effusion between the hospital-acquired influenza A group and the control group(P <0.05).After removing the age and environmental factors,conditional logistic regression analysis showed that : Lymphocytopenia(OR: 3.107;95%CI 1.238-7.796;P =0.016),Hypoalbuminemia(OR: 2.241;95% CI 1.099-4.570;P =0.027)and Pleural effusion(OR: 3.094;95% CI 1.263-7.583;P =0.014)were independent risk factors of hospital acquired influenza A.4.Among the 13 severe influenza A viral pneumonia,4 cases were male and 9 cases were female,aged 25 to 73 years,with a median age of 59 years.(1)Clinical manifestations:Mainly fever,cough,expectoration and shortness of breath;(2)Radiological examination:The median time from the onset to the appearance of radiological examination changes in the lungs was 5.5 days(range 4-7 days),which is characterized by interstitial shadows such as multiple ground-glass or linear,reticular;(3)Laboratory examination: Lymphocyte count and serum albumin decreased in 13 cases,and interleukin-6 and procalcitonin increased in 13 cases;sputum culture and alveolar lavage fluid culture results: 4 patients had positive results,including 1 case of P.maltophilia and Acinetobacter baumannii;1 case of Nearly smooth Candida;1 case of Acinetobacter baumannii;Aspergillus fumigatus was cultured in 1 case of alveolar lavage fluid.The oxygenation index of 8 patients was less than200 mm Hg;(4)Treatment and outcome: All patients were given antiviral and antibacterial drugs,5 cases were given intravenous glucocorticoids,1 case was given antifungal therapy,and 6 cases were given mechanical ventilation.9 patients recovered and were discharged.Conclusions:1.The influenza epidemic in Xi’an has increased significantly year by year,especially in the spring of 2019 the epidemic has increased sharply,and society should pay great attention to it.Influenza occurred throughout the year,and influenza began to prevail in November,especially in the two peak months: December and January,accounting for more than 70%of the total number of cases throughout the year.Vaccination time is the beginning of winter.Preschool children are the most susceptible and should be the focus of the epidemic prevention and control work.2.In the winter and spring,infectious disease clinics(fever clinics),emergency clinics,respiratory clinics,and pediatric clinics need to take measures to deal with a large number of community-acquired influenza A patients.The peak is January.The prevalence of influenza A among hospitalized patients deserves attention,and inpatients in geriatrics,nephrology,and neurology might be more susceptible to influenza virus A infection.3.The risk factors of hospital-acquired influenza A are lymphopenia,hypoalbuminemia,and pleural effusion.Based on these,susceptible individuals can be identified at an early stage,and nosocomial infection control can be targeted.4.Severe influenza A viral pneumonia has the characteristics of rapid onset,rapid progress,susceptibility to bacterial and fungal infection,severe dyspnea,suppressed immune function,and poor prognosis.Early diagnosis of influenza A viral pneumonia,accurate assessment of the condition,timely oxygen therapy and antiviral treatment,prevention and treatment of secondary diseases,and comprehensive treatment measures such as respiratory support,enhancing immunity and nutrition for critically ill,those are the main strategy for successful treatment. |
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