| Objective:To study the clinical epidemiological characteristics,clinical manifestations,disease severity and correlation with environmental and climatic factors of lower respiratory tract infection caused by different subtypes(type A and type B)of respiratory syncytial virus(RSV)in hospitalized children in suzhou,China.Methods:We had collected nasopharyngeal secretions from children with acute lower respiratory tract infection(ALRTI)who were hospitalized in the Children's Hospital of Suzhou University from January 2016 to December 2018.RSV antigens were detected by direct immunofluorescence assay.RSV-RNAs were extracted by membrane extraction,and then cDNA templates were generated by reverse transcription.Each RSV typing was detected by real-time fluorescence quantitative PCR(RT-PCR).Then clinical data of children with positive RSV infection were collected and analyzed in relation to climatic and environmental factors.Results:(1)We classified 1157 RSV-infected children,of which RSV-A subtypes accounted for 60.41%(699 of 1157)and RSV-B subtypes accounted for 39.59%(458 of 1157).It was concluded that the RSV-A subtype was the main one in three years.While the RSV-B was the dominant strain in 2016(RSV-B 58.06%,RSV-A 41.94%,X2=12.834,P=0.01),and there was no statistical difference between the two subtypes in 2017(RSV-A 52.62%,RSV-B 47.38%,X2 = 2.677,P=0.137).In 2018,RSV-A was the dominant company(RSV-A 83.61%,RSV-B 16.39%,X2=27.920,P=0.000).(2)RSV infection was more common in children?6 months of age,accounting for 52.38%(606/1157).There was no significant difference in the distribution of RSV-A and RSV-B subtypes in five age groups(?6 months,?1 years old,?3 years old,?5 years old,and>5 years old)(X2=0.734,P=0.475;X2=0.000,P=1.000;X2=0.439,P=0.620;X2=0.205;P=1.000;X2=0.000;P=1.000).(3)Children included in the study were classified according to different genders.718 cases were male,among which 425 cases(59.19%)were RSV-A and 293 cases(40.81%)were RSV-B.There were 439 female patients,including 274(62.41%)with RSV-A and 165(37.59%)with RSV-B.There was no significant difference in the distribution of the two subtypes between different genders(X2=1.183,P=0.293>0.05).(4)We defined spring,summer,autumn and winter asJanuary to march,April to June,July to September and October to December every year respectively.Winter and spring were the high incidence of RSV infection,accounting for 41.40%(479/1157)and 49.70%(575/1157),respectively.There was no significant difference in the distribution of RSV-A and RSV-B in each quarter(X2=1.657,P=0.252;X2=0.205,P=1.000;X2=0.082,P=1.000;X2=2.422,P=0.157).The difference was statistically significant(X2=11.115,P=0.001)that the RSV-A subtypes were mostly concentrated in winter(58.66%,376/641),and the RSV-B subtypes were mostly concentrated in spring(51.82%,214/413).(5)We randomly selected 353 children with RSV infection with detailed clinical data and analyzed them.There were 233 males,of which 129(55.36%)were RSV-A and 104(44.64%)were RSV-B and there were 120 females,of which 73(60.83%)were RSV-A and 47(39.17%)were RSV-B.Children with different subtypes of infection had no difference in personal history,such as birth weight,mode of birth,full term or not,previous history of eczema,wheezing or allergy,and clinical manifestations,such as cough,wheezing,fever,duration of hospitalization,as well as in clinical pathogenicity severity(P>0.05).(6)?The positive rate of RSV-A was negatively correlated with monthly mean temperature,monthly mean wind speed,total monthly rainfall and O3 concentration(r=-0.586,P=0.000;r=-0.500,P=0.002;r=-0.500,P=0.002;r=-0.644,P=0.000),and positively correlated with concentration of PM2.5,PM 10,N02,S02 and CO(r=0.664,P=0.000;r=0.609,P=0.000;r=0.725,P=0.000;r=0.496,P=0.002;r=0.632,P=0.000),but no correlation with monthly relative humidity and sunshine time(P>0.05),of which monthly mean temperature(adjusted R2=0.551,regression coefficient-0.927,t=-0.358,P=0.001)and concentration of S02 concentration(adjusted R2=0.895 after adjustment,regression coefficient 0.527,t=2.704,P=0.011)had an effect on the positive detection rate of RSV-A Significantly.?The positive detection rate of monthly RSV-B was negatively correlated with monthly average temperature,monthly total rainfall,monthly sunshine duration and O3 concentration(r=-0.573,P=0.000;r=0.366,P=0.028;r=0.402,P=0.015:r=-0.595,P=0.000)and positively correlated with concentration of CO(r=0.554,P=0.000),but not correlated with monthly relative humidity,average wind speed,PM2.5,PM10,N02 and S02(P>0.05).The monthly mean temperature(adjusted R2=0.572,regression coefficient-1.051,t=-1.457,P=0.000)and the concentration of O3(adjusted R2=0.505,regression coefficient-0.659,t=-2.683,P=0.011)had significant effects on the positive detection rate of RSV-B.conclusion:(1)Among the children with RSV infection in Suzhou from 2016 to 2018,the RSV-A subtype was the main one,but the distribution advantages of the two subtypes in different years were not exactly the same.In 2016,the RSV-B subtype was the dominant strain.While there was no statistical difference in the distribution of the two subtypes in 2017.In 2018,the RSV-A subtype was the dominant strain.Winter and spring were high-risk seasons of RSV infection.While there was no significant difference in the distribution of two subtypes in spring,summer,autumn and winter.The RSV-A subtypes were mostly concentrated in winter,and the RSV-B subtypes were mostly concentrated in spring.(2)Children with RSV infection were mainly concentrated in the small age group,especially children less than or equal to 6 months old,and the proportion of children decreased significantly with age.There were no significant differences in children infected with different RSV subtypes in terms of gender,age,individual previous basic conditions,clinical manifestations and disease severity.(3)The positive detection rates of RSV-A and RSV-B in Suzhou area from 2016 to 2018 were correlated with different climatic and environmental factors.The positive detection rates of both subtypes were significantly correlated with temperature.RSV-A was mainly related to temperature,wind speed,rainfall and air pollutant such as PM2.5.PM 10,NO2,SO2,CO and O3,and the positive detection rate of RSV-B was related to temperature,rainfall,sunshine time and O3. |
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